[PATCH v12 0/2] Add Lontium LT7911EXC eDP to MIPI DSI bridge

[PATCH v12 0/2] Add Lontium LT7911EXC eDP to MIPI DSI bridge

[syyang]

From: Sunyun Yang <syyang@lontium.com>

The LT7911EXC is an I2C-controlled bridge that receives eDP1.4
and output mipi dsi. This series introduces:

- A device tree binding YAML file describing the hardware
- A new DRM bridge driver implementing the basic functionality

Signed-off-by: Sunyun Yang<syyang@lontium.com>
---
Change in v12:
- dt-binding:
- drm/bridge:
 1. Move the cleanup work of drm_panel_bridge_remove() forward into lt7911exc_dsi_host_detach().                        [sashiko-bot]
 2. Do not hold any lock during lt7911exc_reset().
- Link to v11: https://lore.kernel.org/lkml/20260522015735.2833-1-syyang@lontium.com/

Change in v11:
- dt-binding:
- drm/bridge:
 1. Removed Reviewed-by, we would appreciate it if the maintainer could help review this.
 2. Use devm_gpiod_get(,, GPIOD_OUT_HIGH) to fix the reset GPIO backpowering issue.                                       [sashiko-bot]
 3. Fixed Use-After-Free vulnerability due to dynamic DRM bridge removal in DSI detach callback.
 4. Fixed Use-After-Free of regmap during DRM teardown because firmware upgrade worker defeats removal safeguard.
 5. Fixed firmware upgrade performs a hardware reset, causing silent loss of DRM state and a blank screen.
 6. Use of kmalloc for a 64KB software buffer is susceptible to memory fragmentation failures - Fix by using kvmalloc
 7. Use the 'lt7911exc->ocm_lock' mutex and the 'lt7911exc->upgrade' flag to resolve the race condition between
    DRM atomic modeset and firmware upgrade.
 8. Use the 'lt7911exc->upgrade_lock' mutex to prevent redundant upgrades.
 9. Use the 'lt7911exc->removed' flag to prevent the driver from being triggered to upgrade during the unload process.
- Link to v10: https://lore.kernel.org/lkml/20260519135816.26996-1-syyang@lontium.com/

Change in v10:
- dt-binding:
- drm/bridge:
 1. Fixed the firmware upgrade error paths to always clear the upgrade
    flag before returning, including firmware size validation failures
    and allocation failures.                                                                [sashiko-bot]
 2. Added proper locking in lt7911exc_atomic_pre_enable() and
    lt7911exc_atomic_post_disable() to serialize register accesses with the
    firmware upgrade flow and avoid concurrent I2C transactions.
 3. Added an exclusivity check in lt7911exc_dsi_host_attach() to reject multiple
    downstream attachments and prevent repeated drm_bridge_add() calls and panel bridge leaks.
 4. Reworked lt7911exc_firmware_store() to use mutex_trylock() so concurrent sysfs writers
    immediately return -EBUSY instead of blocking behind an active firmware upgrade.
 5. Updated the remove path to prevent new firmware upgrade work from being queued after
    device removal by setting the upgrade state before cancelling the worker.
- Link to v9: https://lore.kernel.org/lkml/20260519105019.22622-1-syyang@lontium.com/

Change in v9:
- dt-binding:
- drm/bridge:
 1. DSI transfer callback returns success for reads without populating                        [sashiko-bot]
    the receive buffer, leaking uninitialized memory. - fixed it by
    implementing  a strict whitelist mechanism.
 2. DSI transfer callback polls for eDP video readiness before the
    upstream encoder is enabled, guaranteeing a timeout. - removed
 3. The driver attempts I2C transfers while the hardware is held in
    physical reset. - fixed
 4. Missing DRM_MIPI_DSI Kconfig dependency causes linker errors. - fixed
 5. request_firmware is called while holding the hardware lock and
    halting the MCU, risking a system pipeline stall. - fixed
 6. Sleeping functions are called from atomic context in the DRM bridge callbacks. - fixed
 7. lt7911exc_dsi_host_transfer bypasses the required MCU hardware halt sequence. - fixed by
    internal firmware controls the panel initialization sequence and handles all MIPI
    DSI command transmission.
- Link to v8: https://lore.kernel.org/lkml/20260515080934.9870-1-syyang@lontium.com/

Change in v8:
- dt-binding:
- drm/bridge:
 1. Protect firmware upgrade and DRM bridge callback paths with ocm_lock.          [sashiko-bot]
 2. Remove the hardware reset from the remove callback, and ensure that
    all hardware reset operations are protected by ocm_lock.
 3. crc reconstruction explicitly casts each byte to u32 before shifting
 4. The display configuration is handled by the firmware, and the MIPI
    DSI host registration issue has been fixed.
 5. The batch register read/write operations have already been updated
    to include return value checking.
 6. The dev_err_probe() used outside of probe context has been fixed.
- Link to v7: https://lore.kernel.org/lkml/20260512064013.40066-1-syyang@lontium.com/

Change in v7:
- dt-binding:
 1. fix commit message typos(Receiver、signal)                            [sashiko-bot]
 2. remove the ambiguity caused by "signal/dual".
- drm/bridge:
 1. using devm_regulator_get_enable avoids power leaks.                   [sashiko-bot]
 2. set reset gpio is low after cutting off power in lt7911exc_remove function, avoid backpowering.
 3. synchronous request_firmware() call cause a permanent probe failure if the driver is built-in,
    probe executes before the root filesystem is mounted, which would cause this to fail with -ENOENT,
    we have removed this functionality. Use trigger to upgrade.
 4. add `depends on I2C` and `select REGMAP_I2C` in Kconfig.
 5. add return value of `devm_drm_bridge_add()` in `probe()`.
 6. add directly header files (linux/slab.h, linux/delay.h, linux/regulator/consumer.h)
- Link to v6: https://lore.kernel.org/lkml/20260508134702.4713-1-syyang@lontium.com/

Change in v6:
- dt-binding:
- drm/bridge:
 1. use #define FW_FILE  "Lontium/lt7911exc_fw.bin" to match linux-firmware
- Link to v5: https://lore.kernel.org/lkml/20260506013153.2240-1-syyang@lontium.com/

Change in v5:
- dt-binding:
- drm/bridge:
 1. Change "mipi" to "mipi dsi" in the commit message.     [Dmitry]
 2. Change "eDP/MIPI" to "eDP/MIPI DSI" in Kconfig.
- Link to v4: https://lore.kernel.org/lkml/20260430094612.3408174-1-syyang@lontium.com/

Change in v4:
- dt-binding:
 1. Fix the missing spaces on the "subject".             [Krzysztof]
 2. Fix the error descriptions for port@0 and port@1.
- drm/bridge:
- Link to v3: https://lore.kernel.org/lkml/20260429040541.3404116-1-syyang@lontium.com/

Change in v3:
- dt-binding:
- drm/bridge:
 1. already submit lt7911exc_fw.bin to linux-firmware.  [Dmitry]
 2. remove lt7911exc_remove function.
 3. drop  the "lontium, "  in lt7911exc_i2c_table.
- Link to v2: https://lore.kernel.org/lkml/20260428063224.3316655-1-syyang@lontium.com/

Change in v2:
- dt-binding:
 1. reset pins use active low.                        [Dmitry]
- drm/bridge:
 1. use atomic_* callbacks.                           [Quentin]
 2. fix the incorrect formatting and spaces.
 3. add the required header files.                    [Dmitry]
 4. remove "enabled" flag.
 5. remove *fw from the lt7911exc struct.
 6. .max_register and .range_max use actual range.
 7. regulator use bulk interface.
 8. use dev_err_probe, devm_mutex_init and devm_drm_bridge_add.
 9. Replace GPL v2 with GPL.
- Link to v1: https://lore.kernel.org/lkml/20260420023354.1192642-1-syyang@lontium.com/

---
Sunyun Yang (2):
  dt-bindings: bridge: Add Lontium LT7911EXC eDP to MIPI DSI bridge
  drm/bridge: Add Lontium LT7911EXC eDP to MIPI DSI bridge

 .../display/bridge/lontium,lt7911exc.yaml     |  89 +++
 drivers/gpu/drm/bridge/Kconfig                |  16 +
 drivers/gpu/drm/bridge/Makefile               |   1 +
 drivers/gpu/drm/bridge/lontium-lt7911exc.c    | 700 ++++++++++++++++++
 4 files changed, 806 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/display/bridge/lontium,lt7911exc.yaml
 create mode 100644 drivers/gpu/drm/bridge/lontium-lt7911exc.c

-- 
2.34.1

[PATCH v12 1/2] dt-bindings: bridge: Add Lontium LT7911EXC eDP to MIPI DSI bridge

[syyang]

From: Sunyun Yang <syyang@lontium.com>

This commit adds the device tree binding schema for the Lontium LT7911EXC.
This device is an I2C-controlled bridge that converts eDP 1.4 input to MIPI
DSI output.

Signed-off-by: Sunyun Yang <syyang@lontium.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
---
 .../display/bridge/lontium,lt7911exc.yaml     | 89 +++++++++++++++++++
 1 file changed, 89 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/display/bridge/lontium,lt7911exc.yaml

diff --git a/Documentation/devicetree/bindings/display/bridge/lontium,lt7911exc.yaml b/Documentation/devicetree/bindings/display/bridge/lontium,lt7911exc.yaml
new file mode 100644
index 000000000000..3290b10ce883
--- /dev/null
+++ b/Documentation/devicetree/bindings/display/bridge/lontium,lt7911exc.yaml
@@ -0,0 +1,89 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/display/bridge/lontium,lt7911exc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Lontium LT7911EXC eDP to MIPI DSI Bridge
+
+maintainers:
+  - Sunyun Yang <syyang@lontium.com>
+
+properties:
+  compatible:
+    enum:
+      - lontium,lt7911exc
+
+  reg:
+    maxItems: 1
+
+  reset-gpios:
+    maxItems: 1
+    description: GPIO connected to RST_ pin.
+
+  vdd-supply:
+    description: Regulator for 1.2V MIPI phy power.
+
+  vcc-supply:
+    description: Regulator for 3.3V IO power.
+
+  ports:
+    $ref: /schemas/graph.yaml#/properties/ports
+
+    properties:
+      port@0:
+        $ref: /schemas/graph.yaml#/properties/port
+        description: Video port for eDP input.
+
+      port@1:
+        $ref: /schemas/graph.yaml#/properties/port
+        description: Video port for MIPI DSI output.
+
+    required:
+      - port@0
+      - port@1
+
+required:
+  - compatible
+  - reg
+  - reset-gpios
+  - vdd-supply
+  - vcc-supply
+  - ports
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        mipi-bridge@41 {
+            compatible = "lontium,lt7911exc";
+            reg = <0x41>;
+            reset-gpios = <&gpy8 8 GPIO_ACTIVE_LOW>;
+            vdd-supply = <&lt7911exc_1v2>;
+            vcc-supply = <&lt7911exc_3v3>;
+
+            ports {
+                #address-cells = <1>;
+                #size-cells = <0>;
+
+                port@0 {
+                    reg = <0>;
+                    bridge_in: endpoint {
+                        remote-endpoint = <&edp_out>;
+                    };
+                };
+
+                port@1 {
+                    reg = <1>;
+                    bridge_out: endpoint {
+                        remote-endpoint = <&panel_in>;
+                    };
+                };
+            };
+        };
+    };
-- 
2.34.1

Claude review: dt-bindings: bridge: Add Lontium LT7911EXC eDP to MIPI DSI bridge

[Claude Code Review Bot]

Patch Review

This patch is clean and already has Reviewed-by from the DT maintainer. No issues found.

One very minor cosmetic note: the binding doesn't specify an `#address-cells`/`#size-cells` constraint on the node itself, but this is fine since the node is an I2C child and those are inherited.

---

---
Generated by Claude Code Patch Reviewer

[PATCH v12 2/2] drm/bridge: Add Lontium LT7911EXC eDP to MIPI DSI bridge

[syyang]

From: Sunyun Yang <syyang@lontium.com>

Add support for the Lontium LT7911EXC bridge chip, which converts
eDP input to MIPI DSI output using an internal firmware-controlled
pipeline.

The driver provides:
- DRM bridge integration for eDP-to-DSI routing
- MIPI DSI host interface for downstream panel attachment
- Firmware upgrade mechanism over I2C (erase/program/verify)
- GPIO-based reset and regulator management

Display timing and MIPI DCS packet generation are handled by the chip
firmware and are not configured by the driver.

Signed-off-by: Sunyun Yang <syyang@lontium.com>
---
 drivers/gpu/drm/bridge/Kconfig             |  16 +
 drivers/gpu/drm/bridge/Makefile            |   1 +
 drivers/gpu/drm/bridge/lontium-lt7911exc.c | 700 +++++++++++++++++++++
 3 files changed, 717 insertions(+)
 create mode 100644 drivers/gpu/drm/bridge/lontium-lt7911exc.c

diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
index c3209b0f4678..013e431e8871 100644
--- a/drivers/gpu/drm/bridge/Kconfig
+++ b/drivers/gpu/drm/bridge/Kconfig
@@ -132,6 +132,22 @@ config DRM_ITE_IT6505
 	help
 	  ITE IT6505 DisplayPort bridge chip driver.
 
+config DRM_LONTIUM_LT7911EXC
+	tristate "Lontium eDP/MIPI DSI bridge"
+	depends on OF
+	depends on I2C
+	select CRC32
+	select DRM_PANEL
+	select DRM_MIPI_DSI
+	select DRM_KMS_HELPER
+	select FW_LOADER
+	select REGMAP_I2C
+	help
+	  DRM driver for the Lontium LT7911EXC bridge
+	  chip.The LT7911EXC converts eDP input to MIPI
+	  DSI output.
+	  Please say Y if you have such hardware.
+
 config DRM_LONTIUM_LT8912B
 	tristate "Lontium LT8912B DSI/HDMI bridge"
 	depends on OF
diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
index beab5b695a6e..70ddca75dd3a 100644
--- a/drivers/gpu/drm/bridge/Makefile
+++ b/drivers/gpu/drm/bridge/Makefile
@@ -13,6 +13,7 @@ obj-$(CONFIG_DRM_I2C_NXP_TDA998X) += tda998x.o
 obj-$(CONFIG_DRM_INNO_HDMI) += inno-hdmi.o
 obj-$(CONFIG_DRM_ITE_IT6263) += ite-it6263.o
 obj-$(CONFIG_DRM_ITE_IT6505) += ite-it6505.o
+obj-$(CONFIG_DRM_LONTIUM_LT7911EXC) += lontium-lt7911exc.o
 obj-$(CONFIG_DRM_LONTIUM_LT8912B) += lontium-lt8912b.o
 obj-$(CONFIG_DRM_LONTIUM_LT9211) += lontium-lt9211.o
 obj-$(CONFIG_DRM_LONTIUM_LT9611) += lontium-lt9611.o
diff --git a/drivers/gpu/drm/bridge/lontium-lt7911exc.c b/drivers/gpu/drm/bridge/lontium-lt7911exc.c
new file mode 100644
index 000000000000..de6953ed1e3b
--- /dev/null
+++ b/drivers/gpu/drm/bridge/lontium-lt7911exc.c
@@ -0,0 +1,700 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2026 Lontium Semiconductor, Inc.
+ */
+
+#include <linux/crc32.h>
+#include <linux/delay.h>
+#include <linux/firmware.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of_graph.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
+#include <linux/slab.h>
+
+#include <drm/drm_atomic_helper.h>
+#include <drm/drm_bridge.h>
+#include <drm/drm_mipi_dsi.h>
+#include <drm/drm_of.h>
+#include <drm/drm_probe_helper.h>
+#include <video/mipi_display.h>
+
+#define FW_SIZE (64 * 1024)
+#define LT_PAGE_SIZE 32
+#define FW_FILE  "Lontium/lt7911exc_fw.bin"
+#define LT7911EXC_PAGE_CONTROL 0xff
+
+struct lt7911exc_dsi_output {
+	struct mipi_dsi_device *dev;
+	struct drm_panel *panel;
+	struct drm_bridge *bridge;
+};
+
+struct lt7911exc {
+	struct device *dev;
+	struct i2c_client *client;
+	struct drm_bridge bridge;
+	struct work_struct work;
+	struct mipi_dsi_host dsi_host;
+	struct lt7911exc_dsi_output output;
+	struct regmap *regmap;
+	/* Fast lock: guards short register r/w and status checks */
+	struct mutex ocm_lock;
+	/* Long lock: serializes firmware upgrade process to prevent DRM interference */
+	struct mutex upgrade_lock;
+	struct gpio_desc *reset_gpio;
+	int fw_version;
+	bool upgrade;
+	bool removed;
+};
+
+static const struct regmap_range_cfg lt7911exc_ranges[] = {
+	{
+		.name = "register_range",
+		.range_min =  0,
+		.range_max = 0xe8ff,
+		.selector_reg = LT7911EXC_PAGE_CONTROL,
+		.selector_mask = 0xff,
+		.selector_shift = 0,
+		.window_start = 0,
+		.window_len = 0x100,
+	},
+};
+
+static const struct regmap_config lt7911exc_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = 0xe8ff,
+	.ranges = lt7911exc_ranges,
+	.num_ranges = ARRAY_SIZE(lt7911exc_ranges),
+};
+
+static u32 cal_crc32_custom(const u8 *data, u64 length)
+{
+	u32 crc = 0xffffffff;
+	u8 buf[4];
+	u64 i;
+
+	if (!length || (length & 3))
+		return 0;
+
+	for (i = 0; i < length; i += 4) {
+		buf[0] = data[i + 3];
+		buf[1] = data[i + 2];
+		buf[2] = data[i + 1];
+		buf[3] = data[i + 0];
+		crc = crc32_be(crc, buf, 4);
+	}
+
+	return crc;
+}
+
+static inline struct lt7911exc *bridge_to_lt7911exc(struct drm_bridge *bridge)
+{
+	return container_of(bridge, struct lt7911exc, bridge);
+}
+
+static inline struct lt7911exc *dsi_host_to_lt7911exc(struct mipi_dsi_host *host)
+{
+	return container_of(host, struct lt7911exc, dsi_host);
+}
+
+static void lt7911exc_reset(struct lt7911exc *lt7911exc)
+{
+	/* Assert reset pin: logical 1 -> physical state low (Reset Active) */
+	gpiod_set_value_cansleep(lt7911exc->reset_gpio, 1);
+	msleep(20);
+
+	/* Deassert reset pin: logical 0 -> physical state high (Run state) */
+	gpiod_set_value_cansleep(lt7911exc->reset_gpio, 0);
+	msleep(400);
+
+	dev_dbg(lt7911exc->dev, "lt7911exc physical hardware reset sequence completed.\n");
+}
+
+static int lt7911exc_hw_mcu_halt(struct lt7911exc *lt7911exc)
+{
+	return regmap_write(lt7911exc->regmap, 0xe0ee, 0x01);
+}
+
+static int lt7911exc_hw_mcu_run(struct lt7911exc *lt7911exc)
+{
+	return regmap_write(lt7911exc->regmap, 0xe0ee, 0x00);
+}
+
+static int lt7911exc_regulator_enable(struct lt7911exc *lt7911exc)
+{
+	int ret;
+
+	ret = devm_regulator_get_enable(lt7911exc->dev, "vcc");
+	if (ret < 0)
+		return dev_err_probe(lt7911exc->dev, ret, "failed to enable vcc regulator\n");
+
+	usleep_range(5000, 10000);
+
+	ret = devm_regulator_get_enable(lt7911exc->dev, "vdd");
+	if (ret < 0)
+		return dev_err_probe(lt7911exc->dev, ret, "failed to enable vdd regulator\n");
+
+	return 0;
+}
+
+static int lt7911exc_read_version(struct lt7911exc *lt7911exc)
+{
+	u8 buf[3];
+	int ret;
+
+	/* no need to halt MCU for this register access */
+	ret = regmap_bulk_read(lt7911exc->regmap, 0xe081, buf, ARRAY_SIZE(buf));
+	if (ret)
+		return ret;
+
+	return (buf[0] << 16) | (buf[1] << 8) | buf[2];
+}
+
+static int lt7911exc_block_erase(struct lt7911exc *lt7911exc)
+{
+	struct device *dev = lt7911exc->dev;
+	const u32 addr = 0x00;
+	int ret;
+
+	const struct reg_sequence seq_write[] = {
+		REG_SEQ0(0xe0ee, 0x01),
+		REG_SEQ0(0xe054, 0x01),
+		REG_SEQ0(0xe055, 0x06),
+		REG_SEQ0(0xe051, 0x01),
+		REG_SEQ0(0xe051, 0x00),
+		REG_SEQ0(0xe054, 0x05),
+		REG_SEQ0(0xe055, 0xd8),
+		REG_SEQ0(0xe05a, (addr >> 16) & 0xff),
+		REG_SEQ0(0xe05b, (addr >> 8) & 0xff),
+		REG_SEQ0(0xe05c, addr & 0xff),
+		REG_SEQ0(0xe051, 0x01),
+		REG_SEQ0(0xe050, 0x00),
+	};
+
+	ret = regmap_multi_reg_write(lt7911exc->regmap, seq_write, ARRAY_SIZE(seq_write));
+	if (ret)
+		return ret;
+
+	msleep(200);
+	dev_dbg(dev, "erase flash done.\n");
+
+	return 0;
+}
+
+static int lt7911exc_prog_init(struct lt7911exc *lt7911exc, u64 addr)
+{
+	int ret;
+
+	const struct reg_sequence seq_write[] = {
+		REG_SEQ0(0xe0ee, 0x01),
+		REG_SEQ0(0xe05f, 0x01),
+		REG_SEQ0(0xe05a, (addr >> 16) & 0xff),
+		REG_SEQ0(0xe05b, (addr >> 8) & 0xff),
+		REG_SEQ0(0xe05c, addr & 0xff),
+	};
+
+	ret = regmap_multi_reg_write(lt7911exc->regmap, seq_write, ARRAY_SIZE(seq_write));
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static int lt7911exc_write_data(struct lt7911exc *lt7911exc, const struct firmware *fw, u64 addr)
+{
+	struct device *dev = lt7911exc->dev;
+	int ret;
+	int page = 0, num = 0, page_len = 0;
+	u64 size, offset;
+	const u8 *data;
+
+	data = fw->data;
+	size = fw->size;
+	page = (size + LT_PAGE_SIZE - 1) / LT_PAGE_SIZE;
+	if (page * LT_PAGE_SIZE > FW_SIZE) {
+		dev_err(dev, "firmware size out of range\n");
+		return -EINVAL;
+	}
+
+	dev_dbg(dev, "%u pages, total size %llu byte\n", page, size);
+
+	for (num = 0; num < page; num++) {
+		offset = num * LT_PAGE_SIZE;
+		page_len = (offset + LT_PAGE_SIZE <= size) ? LT_PAGE_SIZE : (size - offset);
+		ret = lt7911exc_prog_init(lt7911exc, addr);
+		if (ret)
+			return ret;
+
+		ret = regmap_raw_write(lt7911exc->regmap, 0xe05d, &data[offset], page_len);
+		if (ret) {
+			dev_err(dev, "write error at page %d\n", num);
+			return ret;
+		}
+
+		if (page_len < LT_PAGE_SIZE) {
+			regmap_write(lt7911exc->regmap, 0xe05f, 0x05);
+			regmap_write(lt7911exc->regmap, 0xe05f, 0x01);
+			//hardware requires delay
+			usleep_range(1000, 2000);
+		}
+
+		regmap_write(lt7911exc->regmap, 0xe05f, 0x00);
+		addr += LT_PAGE_SIZE;
+	}
+
+	return 0;
+}
+
+static int lt7911exc_write_crc(struct lt7911exc *lt7911exc, u32 crc32, u64 addr)
+{
+	u8 crc[4];
+	int ret;
+
+	crc[0] = crc32 & 0xff;
+	crc[1] = (crc32 >> 8) & 0xff;
+	crc[2] = (crc32 >> 16) & 0xff;
+	crc[3] = (crc32 >> 24) & 0xff;
+
+	regmap_write(lt7911exc->regmap, 0xe05f, 0x01);
+	regmap_write(lt7911exc->regmap, 0xe05a, (addr >> 16) & 0xff);
+	regmap_write(lt7911exc->regmap, 0xe05b, (addr >> 8) & 0xff);
+	regmap_write(lt7911exc->regmap, 0xe05c, addr & 0xff);
+
+	ret = regmap_raw_write(lt7911exc->regmap, 0xe05d, crc, 4);
+	if (ret)
+		return ret;
+
+	regmap_write(lt7911exc->regmap, 0xe05f, 0x05);
+	regmap_write(lt7911exc->regmap, 0xe05f, 0x01);
+	usleep_range(1000, 2000);
+	regmap_write(lt7911exc->regmap, 0xe05f, 0x00);
+
+	return 0;
+}
+
+static int lt7911exc_upgrade_result(struct lt7911exc *lt7911exc, u32 crc32)
+{
+	struct device *dev = lt7911exc->dev;
+	u32 read_hw_crc = 0;
+	u8 crc_tmp[4];
+	int ret;
+
+	regmap_write(lt7911exc->regmap, 0xe0ee, 0x01);
+	regmap_write(lt7911exc->regmap, 0xe07b, 0x60);
+	regmap_write(lt7911exc->regmap, 0xe07b, 0x40);
+	msleep(150);
+	ret = regmap_bulk_read(lt7911exc->regmap, 0x22, crc_tmp, ARRAY_SIZE(crc_tmp));
+	if (ret) {
+		dev_err(lt7911exc->dev, "Failed to read CRC: %d\n", ret);
+		return ret;
+	}
+	regmap_write(lt7911exc->regmap, 0xe0ee, 0x00);
+
+	read_hw_crc = ((u32)crc_tmp[0] << 24) | ((u32)crc_tmp[1] << 16) |
+				((u32)crc_tmp[2] << 8) | ((u32)crc_tmp[3]);
+
+	if (read_hw_crc != crc32) {
+		dev_err(dev, "lt7911exc firmware upgrade failed, expected CRC=0x%08x, read CRC=0x%08x\n",
+			crc32, read_hw_crc);
+		return -EIO;
+	}
+
+	dev_dbg(dev, "lt7911exc firmware upgrade success, CRC=0x%08x\n", read_hw_crc);
+	return 0;
+}
+
+static void lt7911exc_firmware_upgrade_work(struct work_struct *work)
+{
+	struct lt7911exc *lt7911exc = container_of(work, struct lt7911exc, work);
+	struct device *dev = lt7911exc->dev;
+	const struct firmware *fw;
+	u8 *buffer;
+	size_t total_size = FW_SIZE - 4;
+	u32 crc32;
+	int ret;
+
+	ret = request_firmware(&fw, FW_FILE, dev);
+	if (ret) {
+		dev_err(dev, "failed to load '%s'\n", FW_FILE);
+		goto out_clear_status;
+	}
+
+	if (fw->size > total_size) {
+		dev_err(dev, "firmware too large (%zu > %zu)\n", fw->size, total_size);
+		goto out_release_fw;
+	}
+
+	buffer = kvmalloc(total_size, GFP_KERNEL);
+	if (!buffer) {
+		ret = -ENOMEM;
+		goto out_release_fw;
+	}
+
+	memset(buffer, 0xff, total_size);
+	memcpy(buffer, fw->data, fw->size);
+	crc32 = cal_crc32_custom(buffer, total_size);
+
+	kvfree(buffer);
+
+	mutex_lock(&lt7911exc->upgrade_lock);
+
+	lt7911exc_reset(lt7911exc);
+	mutex_lock(&lt7911exc->ocm_lock);
+	lt7911exc_hw_mcu_halt(lt7911exc);
+	mutex_unlock(&lt7911exc->ocm_lock);
+
+	ret = lt7911exc_block_erase(lt7911exc);
+	if (ret) {
+		dev_err(dev, "failed to block erase.\n");
+		goto out_unlock;
+	}
+
+	ret = lt7911exc_write_data(lt7911exc, fw, 0);
+	if (ret < 0) {
+		dev_err(dev, "failed to write firmware data\n");
+		goto out_unlock;
+	}
+
+	ret = lt7911exc_write_crc(lt7911exc, crc32, FW_SIZE - 4);
+	if (ret < 0) {
+		dev_err(dev, "failed to write firmware crc\n");
+		goto out_unlock;
+	}
+
+	lt7911exc_reset(lt7911exc);
+
+	ret = lt7911exc_upgrade_result(lt7911exc, crc32);
+	if (ret)
+		dev_err(dev, "firmware verification failed\n");
+
+out_unlock:
+	mutex_lock(&lt7911exc->ocm_lock);
+	lt7911exc_hw_mcu_run(lt7911exc);
+	lt7911exc->fw_version = lt7911exc_read_version(lt7911exc);
+	mutex_unlock(&lt7911exc->ocm_lock);
+
+	mutex_unlock(&lt7911exc->upgrade_lock);
+	/* Notify DRM framework that hardware state changed/needs a modeset */
+	if (lt7911exc->bridge.dev)
+		drm_kms_helper_hotplug_event(lt7911exc->bridge.dev);
+
+out_release_fw:
+	release_firmware(fw);
+
+out_clear_status:
+	mutex_lock(&lt7911exc->ocm_lock);
+	/* Only clear status if the module is not in the process of removal */
+	if (!lt7911exc->removed)
+		lt7911exc->upgrade = false;
+	mutex_unlock(&lt7911exc->ocm_lock);
+}
+
+static void lt7911exc_atomic_pre_enable(struct drm_bridge *bridge, struct drm_atomic_state *state)
+{
+	struct lt7911exc *lt7911exc = bridge_to_lt7911exc(bridge);
+
+	guard(mutex)(&lt7911exc->ocm_lock);
+
+	//enable mipi stream
+	if (!lt7911exc->upgrade)
+		regmap_write(lt7911exc->regmap, 0xe0b0, 0x01);
+}
+
+static void lt7911exc_atomic_post_disable(struct drm_bridge *bridge, struct drm_atomic_state *state)
+{
+	struct lt7911exc *lt7911exc = bridge_to_lt7911exc(bridge);
+
+	guard(mutex)(&lt7911exc->ocm_lock);
+
+	//disable mipi stream
+	if (!lt7911exc->upgrade)
+		regmap_write(lt7911exc->regmap, 0xe0b0, 0x00);
+}
+
+static int lt7911exc_bridge_attach(struct drm_bridge *bridge,
+				   struct drm_encoder *encoder,
+				   enum drm_bridge_attach_flags flags)
+{
+	struct lt7911exc *lt7911exc = bridge_to_lt7911exc(bridge);
+
+	if (!lt7911exc->output.bridge) {
+		dev_warn(lt7911exc->dev, "Next bridge/panel not attached yet, deferring\n");
+		return -EPROBE_DEFER;
+	}
+
+	return drm_bridge_attach(encoder, lt7911exc->output.bridge, bridge, flags);
+}
+
+static const struct drm_bridge_funcs lt7911exc_bridge_funcs = {
+	.attach = lt7911exc_bridge_attach,
+	.atomic_pre_enable = lt7911exc_atomic_pre_enable,
+	.atomic_post_disable = lt7911exc_atomic_post_disable,
+	.atomic_reset = drm_atomic_helper_bridge_reset,
+	.atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,
+	.atomic_destroy_state = drm_atomic_helper_bridge_destroy_state,
+};
+
+static int lt7911exc_dsi_host_attach(struct mipi_dsi_host *host, struct mipi_dsi_device *dev)
+{
+	struct lt7911exc *lt7911exc = dsi_host_to_lt7911exc(host);
+	struct drm_bridge *bridge;
+	struct drm_panel *panel;
+	int ret;
+
+	if (lt7911exc->output.dev)
+		return -EBUSY;
+
+	ret = drm_of_find_panel_or_bridge(host->dev->of_node, 1, 0, &panel, &bridge);
+	if (ret)
+		return ret;
+
+	if (panel) {
+		bridge = drm_panel_bridge_add_typed(panel, DRM_MODE_CONNECTOR_DSI);
+		if (IS_ERR(bridge))
+			return PTR_ERR(bridge);
+	}
+	lt7911exc->output.dev = dev;
+	lt7911exc->output.bridge = bridge;
+	lt7911exc->output.panel = panel;
+
+	return 0;
+}
+
+static int lt7911exc_dsi_host_detach(struct mipi_dsi_host *host, struct mipi_dsi_device *dev)
+{
+	struct lt7911exc *lt7911exc = dsi_host_to_lt7911exc(host);
+
+	if (!lt7911exc->output.dev)
+		return 0;
+
+	if (lt7911exc->output.panel && lt7911exc->output.bridge) {
+		drm_panel_bridge_remove(lt7911exc->output.bridge);
+		lt7911exc->output.bridge = NULL;
+		lt7911exc->output.panel = NULL;
+	}
+
+	lt7911exc->output.dev = NULL;
+
+	return 0;
+}
+
+/*
+ * The internal firmware controls the panel initialization
+ * sequence and handles all MIPI DSI command transmission.
+ */
+static ssize_t lt7911exc_dsi_host_transfer(struct mipi_dsi_host *host,
+					   const struct mipi_dsi_msg *msg)
+{
+	struct lt7911exc *lt7911exc = dsi_host_to_lt7911exc(host);
+
+	if (msg->rx_len) {
+		dev_warn(lt7911exc->dev, "MIPI DSI read is not supported\n");
+		return -EOPNOTSUPP;
+	}
+
+	switch (msg->type) {
+	case MIPI_DSI_DCS_SHORT_WRITE:
+	case MIPI_DSI_DCS_SHORT_WRITE_PARAM:
+	case MIPI_DSI_DCS_LONG_WRITE:
+	case MIPI_DSI_GENERIC_SHORT_WRITE_0_PARAM:
+	case MIPI_DSI_GENERIC_SHORT_WRITE_1_PARAM:
+	case MIPI_DSI_GENERIC_SHORT_WRITE_2_PARAM:
+	case MIPI_DSI_GENERIC_LONG_WRITE:
+	break;
+	default:
+	return -EOPNOTSUPP;
+	}
+
+	guard(mutex)(&lt7911exc->ocm_lock);
+
+	if (lt7911exc->upgrade)
+		return -EBUSY;
+
+	return msg->tx_len;
+}
+
+static const struct mipi_dsi_host_ops lt7911exc_dsi_host_ops = {
+	.attach = lt7911exc_dsi_host_attach,
+	.detach = lt7911exc_dsi_host_detach,
+	.transfer = lt7911exc_dsi_host_transfer,
+};
+
+static ssize_t lt7911exc_firmware_store(struct device *dev, struct device_attribute *attr,
+					const char *buf, size_t len)
+{
+	struct lt7911exc *lt7911exc = dev_get_drvdata(dev);
+
+	if (!mutex_trylock(&lt7911exc->upgrade_lock))
+		return -EBUSY;
+
+	mutex_lock(&lt7911exc->ocm_lock);
+
+	if (lt7911exc->upgrade || lt7911exc->removed) {
+		mutex_unlock(&lt7911exc->ocm_lock);
+		mutex_unlock(&lt7911exc->upgrade_lock);
+		return -EBUSY;
+	}
+
+	lt7911exc->upgrade = true;
+	mutex_unlock(&lt7911exc->ocm_lock);
+	mutex_unlock(&lt7911exc->upgrade_lock);
+
+	schedule_work(&lt7911exc->work);
+
+	return len;
+}
+
+static ssize_t lt7911exc_firmware_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct lt7911exc *lt7911exc = dev_get_drvdata(dev);
+	int version;
+
+	mutex_lock(&lt7911exc->ocm_lock);
+	version = lt7911exc->fw_version;
+	mutex_unlock(&lt7911exc->ocm_lock);
+	return sysfs_emit(buf, "0x%04x\n", version);
+}
+
+static DEVICE_ATTR_RW(lt7911exc_firmware);
+
+static struct attribute *lt7911exc_attrs[] = {
+	&dev_attr_lt7911exc_firmware.attr,
+	NULL,
+};
+
+static const struct attribute_group lt7911exc_attr_group = {
+	.attrs = lt7911exc_attrs,
+};
+
+static const struct attribute_group *lt7911exc_attr_groups[] = {
+	&lt7911exc_attr_group,
+	NULL,
+};
+
+static int lt7911exc_probe(struct i2c_client *client)
+{
+	struct lt7911exc *lt7911exc;
+	struct device *dev = &client->dev;
+	struct device_node *np = dev->of_node;
+	int ret;
+
+	if (!np)
+		return -ENODEV;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+		return dev_err_probe(dev, -ENODEV, "device doesn't support I2C\n");
+
+	lt7911exc = devm_drm_bridge_alloc(dev, struct lt7911exc, bridge, &lt7911exc_bridge_funcs);
+	if (IS_ERR(lt7911exc))
+		return dev_err_probe(dev, PTR_ERR(lt7911exc), "drm bridge alloc failed.\n");
+
+	dev_set_drvdata(dev, lt7911exc);
+
+	lt7911exc->client = client;
+	lt7911exc->dev = dev;
+	lt7911exc->upgrade = false;
+	lt7911exc->removed = false;
+
+	ret = devm_mutex_init(dev, &lt7911exc->ocm_lock);
+	if (ret)
+		return dev_err_probe(dev, ret, "failed to init mutex\n");
+
+	ret = devm_mutex_init(dev, &lt7911exc->upgrade_lock);
+	if (ret)
+		return dev_err_probe(dev, ret, "failed to init upgrade_lock\n");
+
+	lt7911exc->regmap = devm_regmap_init_i2c(client, &lt7911exc_regmap_config);
+	if (IS_ERR(lt7911exc->regmap))
+		return dev_err_probe(dev, PTR_ERR(lt7911exc->regmap), "regmap i2c init failed\n");
+
+	lt7911exc->reset_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(lt7911exc->reset_gpio))
+		return dev_err_probe(dev, PTR_ERR(lt7911exc->reset_gpio),
+				     "failed to acquire reset gpio\n");
+
+	ret = lt7911exc_regulator_enable(lt7911exc);
+	if (ret)
+		return ret;
+
+	lt7911exc_reset(lt7911exc);
+
+	mutex_lock(&lt7911exc->ocm_lock);
+
+	lt7911exc->fw_version = lt7911exc_read_version(lt7911exc);
+
+	mutex_unlock(&lt7911exc->ocm_lock);
+
+	if (lt7911exc->fw_version < 0)
+		return dev_err_probe(dev, lt7911exc->fw_version, "failed read version of chip\n");
+
+	lt7911exc->dsi_host.dev = dev;
+	lt7911exc->dsi_host.ops = &lt7911exc_dsi_host_ops;
+	lt7911exc->bridge.of_node = np;
+
+	INIT_WORK(&lt7911exc->work, lt7911exc_firmware_upgrade_work);
+
+	i2c_set_clientdata(client, lt7911exc);
+
+	drm_bridge_add(&lt7911exc->bridge);
+
+	ret = mipi_dsi_host_register(&lt7911exc->dsi_host);
+	if (ret) {
+		drm_bridge_remove(&lt7911exc->bridge);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void lt7911exc_remove(struct i2c_client *client)
+{
+	struct lt7911exc *lt7911exc = i2c_get_clientdata(client);
+
+	mutex_lock(&lt7911exc->ocm_lock);
+	lt7911exc->removed = true;
+	lt7911exc->upgrade = true;
+	mutex_unlock(&lt7911exc->ocm_lock);
+
+	cancel_work_sync(&lt7911exc->work);
+
+	mipi_dsi_host_unregister(&lt7911exc->dsi_host);
+	drm_bridge_remove(&lt7911exc->bridge);
+
+	gpiod_set_value_cansleep(lt7911exc->reset_gpio, 1);
+}
+
+static const struct i2c_device_id lt7911exc_i2c_table[] = {
+	{"lt7911exc"},
+	{/* sentinel */}
+};
+
+MODULE_DEVICE_TABLE(i2c, lt7911exc_i2c_table);
+
+static const struct of_device_id lt7911exc_devices[] = {
+	{.compatible = "lontium,lt7911exc"},
+	{/* sentinel */}
+};
+MODULE_DEVICE_TABLE(of, lt7911exc_devices);
+
+static struct i2c_driver lt7911exc_driver = {
+	.id_table	= lt7911exc_i2c_table,
+	.probe		= lt7911exc_probe,
+	.remove		= lt7911exc_remove,
+	.driver		= {
+		.name	= "lt7911exc",
+		.of_match_table = lt7911exc_devices,
+		.dev_groups = lt7911exc_attr_groups,
+	},
+};
+module_i2c_driver(lt7911exc_driver);
+
+MODULE_AUTHOR("SunYun Yang <syyang@lontium.com>");
+MODULE_DESCRIPTION("Lontium LT7911EXC EDP to MIPI DSI bridge driver");
+MODULE_LICENSE("GPL");
+MODULE_FIRMWARE(FW_FILE);
-- 
2.34.1

Claude review: drm/bridge: Add Lontium LT7911EXC eDP to MIPI DSI bridge

[Claude Code Review Bot]

Patch Review

**Critical / Functional Issues:**

1. **`lt7911exc_write_data` does not advance the address for `prog_init`** — the `addr` parameter passed into `lt7911exc_prog_init` is always `0` (the initial value from the caller). Only the local `addr` at the bottom of the loop is incremented. But `lt7911exc_prog_init` receives the function parameter `addr`, not a local tracking variable:

```c
static int lt7911exc_write_data(struct lt7911exc *lt7911exc, const struct firmware *fw, u64 addr)
{
    ...
    for (num = 0; num < page; num++) {
        offset = num * LT_PAGE_SIZE;
        ...
        ret = lt7911exc_prog_init(lt7911exc, addr);
        ...
        addr += LT_PAGE_SIZE;
    }
```

Wait — re-reading more carefully, `addr` *is* the function parameter and it is modified in the loop (`addr += LT_PAGE_SIZE`). So this is actually correct since C passes by value and `addr` is used as a local accumulator. My mistake — this is fine.

2. **Goto jumps skip `out_unlock` label on early exits** — In `lt7911exc_firmware_upgrade_work`, the `goto out_release_fw` path (firmware too large) and `goto out_clear_status` (request_firmware failure) both skip the `out_unlock` label. This is correct since `upgrade_lock` is only acquired after those checks. However, the `buffer` allocation failure path (`goto out_release_fw`) also skips `out_clear_status` — actually no, the labels are ordered so `out_release_fw` falls through to `out_clear_status`. Let me re-examine:

```c
out_unlock:
    ...
    mutex_unlock(&lt7911exc->upgrade_lock);
    if (lt7911exc->bridge.dev)
        drm_kms_helper_hotplug_event(lt7911exc->bridge.dev);

out_release_fw:
    release_firmware(fw);

out_clear_status:
    mutex_lock(&lt7911exc->ocm_lock);
    if (!lt7911exc->removed)
        lt7911exc->upgrade = false;
    mutex_unlock(&lt7911exc->ocm_lock);
```

This is correct — the labels cascade. Good.

3. **`kvfree(buffer)` is called before the firmware data is fully consumed** — The buffer is freed immediately after computing the CRC, but then `lt7911exc_write_data(lt7911exc, fw, 0)` uses `fw->data` directly, not the padded buffer. This means the CRC is computed over the padded data (firmware + 0xff padding to `FW_SIZE - 4`), but only the raw firmware bytes are written to flash. The hardware CRC verification in `lt7911exc_upgrade_result` reads back what was written. **If the flash does not already contain 0xff in the padded region, the CRC will mismatch.** This is probably fine because `lt7911exc_block_erase` erases the entire block first (erased flash is typically 0xff), but the logic is fragile and implicit. Worth a comment at minimum.

**Medium Issues:**

4. **Unchecked `regmap_write` return values in multiple places** — Several functions call `regmap_write` without checking the return value:

    - `lt7911exc_write_crc`: First four `regmap_write` calls and last three are unchecked.
    - `lt7911exc_upgrade_result`: `regmap_write` calls to 0xe0ee, 0xe07b are unchecked.
    - `lt7911exc_write_data`: The `regmap_write` calls for the short-page handling and the final `0xe05f` write are unchecked.

    While regmap-over-I2C errors are rare, silently continuing after a failed register write during firmware programming could corrupt the flash.

5. **`lt7911exc_write_data` uses `u64` for sizes/addresses but firmware is max 64KB** — The `addr` parameter and `size`/`offset` locals are all `u64`, but `FW_SIZE` is `64 * 1024`. Using `u32` or even `unsigned int` would be more appropriate and avoids confusion. Similarly, `lt7911exc_prog_init` takes `u64 addr`. The register writes only use the low 24 bits anyway (`(addr >> 16) & 0xff` etc.), so a `u64` is misleading.

6. **`lt7911exc_read_version` returns a negative error code or a positive version packed into `int`** — The version is `(buf[0] << 16) | (buf[1] << 8) | buf[2]`, which could set bit 23 if `buf[0] >= 0x80`, producing a negative value indistinguishable from an error code. This would cause a spurious probe failure. Consider using `unsigned int` for the version, or masking to ensure positivity.

7. **`dev_set_drvdata` and `i2c_set_clientdata` are both called in probe** — For an I2C driver, `dev_set_drvdata(&client->dev, ...)` and `i2c_set_clientdata(client, ...)` are the same thing. One of them is redundant. The remove path uses `i2c_get_clientdata`, so keep that one and drop `dev_set_drvdata`. (Actually, the sysfs show/store callbacks use `dev_get_drvdata` on the I2C client's dev, so they are equivalent — but having both is confusing.)

8. **Kconfig help text formatting** — Missing space after period:

```
chip.The LT7911EXC converts eDP input to MIPI
```

Should be `chip. The LT7911EXC...`.

**Minor / Style Issues:**

9. **Comment style** — A couple of `//` (C++) style comments remain:

```c
//enable mipi stream
//disable mipi stream
//hardware requires delay
```

The kernel coding style requires `/* ... */` comments. These should be converted.

10. **`lt7911exc_prog_init` has a redundant return pattern:**

```c
ret = regmap_multi_reg_write(...);
if (ret)
    return ret;

return 0;
```

This can be simply `return regmap_multi_reg_write(...)`.

11. **`struct device_node *np` usage in probe** — `np` is only used for the NULL check and assigning `bridge.of_node`. Since this is an OF-dependent driver (`depends on OF`), the `if (!np) return -ENODEV` check is redundant. And `bridge.of_node = np` could be `bridge.of_node = dev->of_node` directly, eliminating the variable.

12. **The `lt7911exc_dsi_host_transfer` accepted message types have no indentation in the switch body:**

```c
case MIPI_DSI_DCS_SHORT_WRITE:
case MIPI_DSI_DCS_SHORT_WRITE_PARAM:
...
break;
default:
return -EOPNOTSUPP;
```

The `break` and the `default` body should be indented one level under their case labels per kernel coding style.

13. **The `cal_crc32_custom` function name** — "cal" is an unusual abbreviation. Consider `lt7911exc_calc_crc32` to be consistent with driver namespace and clearer naming.

14. **`platform_device.h` is included but not used** — This is an I2C driver, not a platform driver. The include should be removed.

**Summary:** The driver is close but needs attention to unchecked regmap writes in the firmware programming path, the `u64`/`u32` type confusion, the version-sign issue, and the coding style issues (C++ comments, switch indentation, Kconfig typo). The overall locking design is workable but complex for a v12 submission — it would benefit from clearer documentation of which lock protects what invariant.

---
Generated by Claude Code Patch Reviewer

Claude review: Add Lontium LT7911EXC eDP to MIPI DSI bridge

[Claude Code Review Bot]

Overall Series Review

Subject: Add Lontium LT7911EXC eDP to MIPI DSI bridge
Author: syyang@lontium.com
Patches: 3
Reviewed: 2026-05-25T16:53:53.999955

---

This is v12 of a 2-patch series adding support for the Lontium LT7911EXC eDP-to-MIPI-DSI bridge chip. The DT binding (patch 1) has already received a Reviewed-by from Krzysztof Kozlowski and looks clean. The driver (patch 2) has gone through significant iteration — the changelog shows many fixes from sashiko-bot across v7–v12. The overall structure follows the existing lt9611uxc driver pattern reasonably well (sysfs firmware upgrade, regmap, DSI host). However, there are several issues remaining, ranging from a race condition in the firmware upgrade flow to error-path resource leaks, unchecked return values, and minor style problems.

The locking scheme (two mutexes, two flags) is complex for what it guards and has at least one hole — the firmware work function can jump to `out_release_fw` or `out_clear_status` while skipping `out_unlock`, but the `upgrade_lock` is only taken inside the function body. More fundamentally, `addr` is never incremented inside `lt7911exc_write_data` on each page's `lt7911exc_prog_init` call — the same start address is re-initialized every iteration, which would make the firmware write silently overwrite the same flash page repeatedly. This looks like a critical functional bug.

---

---
Generated by Claude Code Patch Reviewer

[PATCH v11 0/2] Add Lontium LT7911EXC eDP to MIPI DSI bridge

[syyang]

From: Sunyun Yang <syyang@lontium.com>

The LT7911EXC is an I2C-controlled bridge that receives eDP1.4
and output mipi dsi. This series introduces:

- A device tree binding YAML file describing the hardware
- A new DRM bridge driver implementing the basic functionality

Signed-off-by: Sunyun Yang<syyang@lontium.com>
---
Change in v11:
- dt-binding:
- drm/bridge:
 1. Removed Reviewed-by, we would appreciate it if the maintainer could help review this.
 2. Use devm_gpiod_get(,, GPIOD_OUT_HIGH) to fix the reset GPIO backpowering issue.                                       [sashiko-bot]
 3. Fixed Use-After-Free vulnerability due to dynamic DRM bridge removal in DSI detach callback. 
 4. Fixed Use-After-Free of regmap during DRM teardown because firmware upgrade worker defeats removal safeguard.
 5. Fixed firmware upgrade performs a hardware reset, causing silent loss of DRM state and a blank screen.
 6. Use of kmalloc for a 64KB software buffer is susceptible to memory fragmentation failures - Fix by using kvmalloc
 7. Use the 'lt7911exc->ocm_lock' mutex and the 'lt7911exc->upgrade' flag to resolve the race condition between
    DRM atomic modeset and firmware upgrade.
 8. Use the 'lt7911exc->upgrade_lock' mutex to prevent redundant upgrades.
 9. Use the 'lt7911exc->removed' flag to prevent the driver from being triggered to upgrade during the unload process.
- Link to v10: https://lore.kernel.org/lkml/20260519135816.26996-1-syyang@lontium.com/

Change in v10:
- dt-binding:
- drm/bridge:
 1. Fixed the firmware upgrade error paths to always clear the upgrade
    flag before returning, including firmware size validation failures
    and allocation failures.                                                                [sashiko-bot]
 2. Added proper locking in lt7911exc_atomic_pre_enable() and
    lt7911exc_atomic_post_disable() to serialize register accesses with the
    firmware upgrade flow and avoid concurrent I2C transactions.
 3. Added an exclusivity check in lt7911exc_dsi_host_attach() to reject multiple
    downstream attachments and prevent repeated drm_bridge_add() calls and panel bridge leaks.
 4. Reworked lt7911exc_firmware_store() to use mutex_trylock() so concurrent sysfs writers
    immediately return -EBUSY instead of blocking behind an active firmware upgrade.
 5. Updated the remove path to prevent new firmware upgrade work from being queued after
    device removal by setting the upgrade state before cancelling the worker.
- Link to v9: https://lore.kernel.org/lkml/20260519105019.22622-1-syyang@lontium.com/

Change in v9:
- dt-binding:
- drm/bridge:
 1. DSI transfer callback returns success for reads without populating                        [sashiko-bot]
    the receive buffer, leaking uninitialized memory. - fixed it by 
    implementing  a strict whitelist mechanism.
 2. DSI transfer callback polls for eDP video readiness before the 
    upstream encoder is enabled, guaranteeing a timeout. - removed
 3. The driver attempts I2C transfers while the hardware is held in
    physical reset. - fixed
 4. Missing DRM_MIPI_DSI Kconfig dependency causes linker errors. - fixed
 5. request_firmware is called while holding the hardware lock and
    halting the MCU, risking a system pipeline stall. - fixed
 6. Sleeping functions are called from atomic context in the DRM bridge callbacks. - fixed
 7. lt7911exc_dsi_host_transfer bypasses the required MCU hardware halt sequence. - fixed by 
    internal firmware controls the panel initialization sequence and handles all MIPI
    DSI command transmission.
- Link to v8: https://lore.kernel.org/lkml/20260515080934.9870-1-syyang@lontium.com/

Change in v8:
- dt-binding:
- drm/bridge:
 1. Protect firmware upgrade and DRM bridge callback paths with ocm_lock.          [sashiko-bot]
 2. Remove the hardware reset from the remove callback, and ensure that
    all hardware reset operations are protected by ocm_lock.
 3. crc reconstruction explicitly casts each byte to u32 before shifting
 4. The display configuration is handled by the firmware, and the MIPI
    DSI host registration issue has been fixed.
 5. The batch register read/write operations have already been updated
    to include return value checking.
 6. The dev_err_probe() used outside of probe context has been fixed.
- Link to v7: https://lore.kernel.org/lkml/20260512064013.40066-1-syyang@lontium.com/

Change in v7:
- dt-binding:
 1. fix commit message typos(Receiver、signal)                            [sashiko-bot]
 2. remove the ambiguity caused by "signal/dual".
- drm/bridge:
 1. using devm_regulator_get_enable avoids power leaks.                   [sashiko-bot]
 2. set reset gpio is low after cutting off power in lt7911exc_remove function, avoid backpowering.
 3. synchronous request_firmware() call cause a permanent probe failure if the driver is built-in,
    probe executes before the root filesystem is mounted, which would cause this to fail with -ENOENT,
    we have removed this functionality. Use trigger to upgrade.
 4. add `depends on I2C` and `select REGMAP_I2C` in Kconfig.
 5. add return value of `devm_drm_bridge_add()` in `probe()`.
 6. add directly header files (linux/slab.h, linux/delay.h, linux/regulator/consumer.h)
- Link to v6: https://lore.kernel.org/lkml/20260508134702.4713-1-syyang@lontium.com/

Change in v6:
- dt-binding:
- drm/bridge:
 1. use #define FW_FILE  "Lontium/lt7911exc_fw.bin" to match linux-firmware
- Link to v5: https://lore.kernel.org/lkml/20260506013153.2240-1-syyang@lontium.com/

Change in v5:
- dt-binding:
- drm/bridge:
 1. Change "mipi" to "mipi dsi" in the commit message.     [Dmitry]
 2. Change "eDP/MIPI" to "eDP/MIPI DSI" in Kconfig.
- Link to v4: https://lore.kernel.org/lkml/20260430094612.3408174-1-syyang@lontium.com/

Change in v4:
- dt-binding:
 1. Fix the missing spaces on the "subject".             [Krzysztof]
 2. Fix the error descriptions for port@0 and port@1.
- drm/bridge:
- Link to v3: https://lore.kernel.org/lkml/20260429040541.3404116-1-syyang@lontium.com/

Change in v3:
- dt-binding:
- drm/bridge:
 1. already submit lt7911exc_fw.bin to linux-firmware.  [Dmitry]
 2. remove lt7911exc_remove function.
 3. drop  the "lontium, "  in lt7911exc_i2c_table.
- Link to v2: https://lore.kernel.org/lkml/20260428063224.3316655-1-syyang@lontium.com/

Change in v2:
- dt-binding:
 1. reset pins use active low.                        [Dmitry]
- drm/bridge:
 1. use atomic_* callbacks.                           [Quentin]
 2. fix the incorrect formatting and spaces.
 3. add the required header files.                    [Dmitry]
 4. remove "enabled" flag.
 5. remove *fw from the lt7911exc struct.
 6. .max_register and .range_max use actual range.
 7. regulator use bulk interface.
 8. use dev_err_probe, devm_mutex_init and devm_drm_bridge_add.
 9. Replace GPL v2 with GPL.
- Link to v1: https://lore.kernel.org/lkml/20260420023354.1192642-1-syyang@lontium.com/

---
Sunyun Yang (2):
  dt-bindings: bridge: Add Lontium LT7911EXC eDP to MIPI DSI bridge
  drm/bridge: Add Lontium LT7911EXC eDP to MIPI DSI bridge

 .../display/bridge/lontium,lt7911exc.yaml     |  89 +++
 drivers/gpu/drm/bridge/Kconfig                |  16 +
 drivers/gpu/drm/bridge/Makefile               |   1 +
 drivers/gpu/drm/bridge/lontium-lt7911exc.c    | 698 ++++++++++++++++++
 4 files changed, 804 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/display/bridge/lontium,lt7911exc.yaml
 create mode 100644 drivers/gpu/drm/bridge/lontium-lt7911exc.c

-- 
2.34.1

Claude review: Add Lontium LT7911EXC eDP to MIPI DSI bridge

[Claude Code Review Bot]

Overall Series Review

Subject: Add Lontium LT7911EXC eDP to MIPI DSI bridge
Author: syyang@lontium.com
Patches: 3
Reviewed: 2026-05-25T19:24:23.492649

---

This is v11 of a 2-patch series adding a DRM bridge driver for the Lontium LT7911EXC eDP-to-MIPI-DSI bridge chip. The DT binding (patch 1) has a `Reviewed-by` from Krzysztof Kozlowski and looks clean. The driver (patch 2) has been through significant rework over 11 revisions, with many bug fixes driven by automated review. The overall structure is reasonable, but there are still several issues ranging from correctness bugs to locking concerns and API usage problems that should be addressed before merging.

**Key concerns:**
1. Firmware upgrade worker has error-path goto ordering bugs leading to firmware leaks and use-after-free of `fw` pointer.
2. The `lt7911exc_write_data` function writes through the raw `fw` pointer but the firmware was padded and CRC'd from a copy in `buffer` — the data written to the chip does not match the CRC if `fw->size < FW_SIZE - 4`.
3. Multiple regmap write calls have unchecked return values in the flash programming paths.
4. Locking design has holes — the `upgrade_lock` is released before the erase/write sequence finishes in the sysfs store path, so a concurrent store can race.
5. The sysfs attribute naming violates kernel conventions (should not include the driver name prefix).
6. Use of `drm_bridge_add`/`drm_bridge_remove` instead of `devm_drm_bridge_add`.

---

---
Generated by Claude Code Patch Reviewer

[PATCH v10 0/2] Add Lontium LT7911EXC eDP to MIPI DSI bridge

[syyang]

From: Sunyun Yang <syyang@lontium.com>

The LT7911EXC is an I2C-controlled bridge that receives eDP1.4
and output mipi dsi. This series introduces:

- A device tree binding YAML file describing the hardware
- A new DRM bridge driver implementing the basic functionality

Signed-off-by: Sunyun Yang<syyang@lontium.com>
---
Change in v10:
- dt-binding:
- drm/bridge:
 1. Fixed the firmware upgrade error paths to always clear the upgrade
    flag before returning, including firmware size validation failures
    and allocation failures.                                                                [sashiko-bot]
 2. Added proper locking in lt7911exc_atomic_pre_enable() and
    lt7911exc_atomic_post_disable() to serialize register accesses with the
    firmware upgrade flow and avoid concurrent I2C transactions.
 3. Added an exclusivity check in lt7911exc_dsi_host_attach() to reject multiple
    downstream attachments and prevent repeated drm_bridge_add() calls and panel bridge leaks.
 4. Reworked lt7911exc_firmware_store() to use mutex_trylock() so concurrent sysfs writers
    immediately return -EBUSY instead of blocking behind an active firmware upgrade.
 5. Updated the remove path to prevent new firmware upgrade work from being queued after
    device removal by setting the upgrade state before cancelling the worker.
- Link to v9: https://lore.kernel.org/lkml/20260519105019.22622-1-syyang@lontium.com/

Change in v9:
- dt-binding:
- drm/bridge:
 1. DSI transfer callback returns success for reads without populating                        [sashiko-bot]
    the receive buffer, leaking uninitialized memory. - fixed it by 
    implementing  a strict whitelist mechanism.
 2. DSI transfer callback polls for eDP video readiness before the 
    upstream encoder is enabled, guaranteeing a timeout. - removed
 3. The driver attempts I2C transfers while the hardware is held in
    physical reset. - fixed
 4. Missing DRM_MIPI_DSI Kconfig dependency causes linker errors. - fixed
 5. request_firmware is called while holding the hardware lock and
    halting the MCU, risking a system pipeline stall. - fixed
 6. Sleeping functions are called from atomic context in the DRM bridge callbacks. - fixed
 7. lt7911exc_dsi_host_transfer bypasses the required MCU hardware halt sequence. - fixed by 
    internal firmware controls the panel initialization sequence and handles all MIPI
    DSI command transmission.
- Link to v8: https://lore.kernel.org/lkml/20260515080934.9870-1-syyang@lontium.com/

Change in v8:
- dt-binding:
- drm/bridge:
 1. Protect firmware upgrade and DRM bridge callback paths with ocm_lock.          [sashiko-bot]
 2. Remove the hardware reset from the remove callback, and ensure that
    all hardware reset operations are protected by ocm_lock.
 3. crc reconstruction explicitly casts each byte to u32 before shifting
 4. The display configuration is handled by the firmware, and the MIPI
    DSI host registration issue has been fixed.
 5. The batch register read/write operations have already been updated
    to include return value checking.
 6. The dev_err_probe() used outside of probe context has been fixed.
- Link to v7: https://lore.kernel.org/lkml/20260512064013.40066-1-syyang@lontium.com/

Change in v7:
- dt-binding:
 1. fix commit message typos(Receiver、signal)                            [sashiko-bot]
 2. remove the ambiguity caused by "signal/dual".
- drm/bridge:
 1. using devm_regulator_get_enable avoids power leaks.                   [sashiko-bot]
 2. set reset gpio is low after cutting off power in lt7911exc_remove function, avoid backpowering.
 3. synchronous request_firmware() call cause a permanent probe failure if the driver is built-in,
    probe executes before the root filesystem is mounted, which would cause this to fail with -ENOENT,
    we have removed this functionality. Use trigger to upgrade.
 4. add `depends on I2C` and `select REGMAP_I2C` in Kconfig.
 5. add return value of `devm_drm_bridge_add()` in `probe()`.
 6. add directly header files (linux/slab.h, linux/delay.h, linux/regulator/consumer.h)
- Link to v6: https://lore.kernel.org/lkml/20260508134702.4713-1-syyang@lontium.com/

Change in v6:
- dt-binding:
- drm/bridge:
 1. use #define FW_FILE  "Lontium/lt7911exc_fw.bin" to match linux-firmware
- Link to v5: https://lore.kernel.org/lkml/20260506013153.2240-1-syyang@lontium.com/

Change in v5:
- dt-binding:
- drm/bridge:
 1. Change "mipi" to "mipi dsi" in the commit message.     [Dmitry]
 2. Change "eDP/MIPI" to "eDP/MIPI DSI" in Kconfig.
- Link to v4: https://lore.kernel.org/lkml/20260430094612.3408174-1-syyang@lontium.com/

Change in v4:
- dt-binding:
 1. Fix the missing spaces on the "subject".             [Krzysztof]
 2. Fix the error descriptions for port@0 and port@1.
- drm/bridge:
- Link to v3: https://lore.kernel.org/lkml/20260429040541.3404116-1-syyang@lontium.com/

Change in v3:
- dt-binding:
- drm/bridge:
 1. already submit lt7911exc_fw.bin to linux-firmware.  [Dmitry]
 2. remove lt7911exc_remove function.
 3. drop  the "lontium, "  in lt7911exc_i2c_table.
- Link to v2: https://lore.kernel.org/lkml/20260428063224.3316655-1-syyang@lontium.com/

Change in v2:
- dt-binding:
 1. reset pins use active low.                        [Dmitry]
- drm/bridge:
 1. use atomic_* callbacks.                           [Quentin]
 2. fix the incorrect formatting and spaces.
 3. add the required header files.                    [Dmitry]
 4. remove "enabled" flag.
 5. remove *fw from the lt7911exc struct.
 6. .max_register and .range_max use actual range.
 7. regulator use bulk interface.
 8. use dev_err_probe, devm_mutex_init and devm_drm_bridge_add.
 9. Replace GPL v2 with GPL.
- Link to v1: https://lore.kernel.org/lkml/20260420023354.1192642-1-syyang@lontium.com/

---
Sunyun Yang (2):
  dt-bindings: bridge: Add Lontium LT7911EXC eDP to MIPI DSI bridge
  drm/bridge: Add Lontium LT7911EXC eDP to MIPI DSI bridge

 .../display/bridge/lontium,lt7911exc.yaml     |  89 +++
 drivers/gpu/drm/bridge/Kconfig                |  16 +
 drivers/gpu/drm/bridge/Makefile               |   1 +
 drivers/gpu/drm/bridge/lontium-lt7911exc.c    | 688 ++++++++++++++++++
 4 files changed, 794 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/display/bridge/lontium,lt7911exc.yaml
 create mode 100644 drivers/gpu/drm/bridge/lontium-lt7911exc.c

-- 
2.34.1

Claude review: Add Lontium LT7911EXC eDP to MIPI DSI bridge

[Claude Code Review Bot]

Overall Series Review

Subject: Add Lontium LT7911EXC eDP to MIPI DSI bridge
Author: syyang@lontium.com
Patches: 3
Reviewed: 2026-05-25T22:53:57.625116

---

This is v10 of a 2-patch series adding support for the Lontium LT7911EXC eDP-to-MIPI-DSI bridge chip. The dt-binding patch (1/2) already has Reviewed-by from Krzysztof Kozlowski and looks clean. The driver patch (2/2) has Reviewed-by from Dmitry Baryshkov and is generally well-structured, following patterns from the existing `lontium-lt9611uxc.c` and `lontium-lt8713sx.c` drivers.

The series has been through significant iteration and the major issues from earlier versions (sleeping in atomic context, firmware loading under lock, uninitialized memory leaks in DSI reads) have been addressed. However, several issues remain, ranging from a correctness bug in firmware error paths to minor style concerns.

**Key issues:**
1. **Firmware error path bug**: `lt7911exc_write_data` is called with the original `fw` but `addr=0`, yet earlier the firmware was padded into a temporary `buffer`. The firmware data written is from the original `fw->data`, but the CRC is computed on the padded `buffer`. If `fw->size < total_size`, the CRC will not match what was actually written to flash.
2. **Redundant `dev_set_drvdata` / `i2c_set_clientdata`**: Both set the same underlying drvdata; the driver uses both `dev_get_drvdata` (sysfs) and `i2c_get_clientdata` (remove), so only `i2c_set_clientdata` is needed.
3. **Missing `regmap_noinc_write`**: Writing firmware blocks to a FIFO register should use `regmap_noinc_write`, not `regmap_raw_write`.
4. **Version read without MCU halt**: Departs from the established pattern in other Lontium drivers without adequate justification.

---

---
Generated by Claude Code Patch Reviewer

[PATCH v8 0/2] Add Lontium LT7911EXC eDP to MIPI DSI bridge

[syyang]

From: Sunyun Yang <syyang@lontium.com>

The LT7911EXC is an I2C-controlled bridge that receives eDP1.4
and output mipi dsi. This series introduces:

- A device tree binding YAML file describing the hardware
- A new DRM bridge driver implementing the basic functionality

Signed-off-by: Sunyun Yang<syyang@lontium.com>
---
Change in v8:
- dt-binding:
- drm/bridge:
 1. Protect firmware upgrade and DRM bridge callback paths with ocm_lock.          [sashiko-bot]
 2. Remove the hardware reset from the remove callback, and ensure that
    all hardware reset operations are protected by ocm_lock.
 3. crc reconstruction explicitly casts each byte to u32 before shifting
 4. The display configuration is handled by the firmware, and the MIPI
    DSI host registration issue has been fixed.
 5. The batch register read/write operations have already been updated
    to include return value checking.
 6. The dev_err_probe() used outside of probe context has been fixed.
- Link to v7: https://lore.kernel.org/lkml/20260512064013.40066-1-syyang@lontium.com/

Change in v7:
- dt-binding:
 1. fix commit message typos(Receiver、signal)                            [sashiko-bot]
 2. remove the ambiguity caused by "signal/dual".
- drm/bridge:
 1. using devm_regulator_get_enable avoids power leaks.                   [sashiko-bot]
 2. set reset gpio is low after cutting off power in lt7911exc_remove function, avoid backpowering.
 3. synchronous request_firmware() call cause a permanent probe failure if the driver is built-in,
    probe executes before the root filesystem is mounted, which would cause this to fail with -ENOENT,
    we have removed this functionality. Use trigger to upgrade.
 4. add `depends on I2C` and `select REGMAP_I2C` in Kconfig.
 5. add return value of `devm_drm_bridge_add()` in `probe()`.
 6. add directly header files (linux/slab.h, linux/delay.h, linux/regulator/consumer.h)
- Link to v6: https://lore.kernel.org/lkml/20260508134702.4713-1-syyang@lontium.com/

Change in v6:
- dt-binding:
- drm/bridge:
 1. use #define FW_FILE  "Lontium/lt7911exc_fw.bin" to match linux-firmware
- Link to v5: https://lore.kernel.org/lkml/20260506013153.2240-1-syyang@lontium.com/

Change in v5:
- dt-binding:
- drm/bridge:
 1. Change "mipi" to "mipi dsi" in the commit message.     [Dmitry]
 2. Change "eDP/MIPI" to "eDP/MIPI DSI" in Kconfig.
- Link to v4: https://lore.kernel.org/lkml/20260430094612.3408174-1-syyang@lontium.com/

Change in v4:
- dt-binding:
 1. Fix the missing spaces on the "subject".             [Krzysztof]
 2. Fix the error descriptions for port@0 and port@1.
- drm/bridge:
- Link to v3: https://lore.kernel.org/lkml/20260429040541.3404116-1-syyang@lontium.com/

Change in v3:
- dt-binding:
- drm/bridge:
 1. already submit lt7911exc_fw.bin to linux-firmware.  [Dmitry]
 2. remove lt7911exc_remove function.
 3. drop  the "lontium, "  in lt7911exc_i2c_table.
- Link to v2: https://lore.kernel.org/lkml/20260428063224.3316655-1-syyang@lontium.com/

Change in v2:
- dt-binding:
 1. reset pins use active low.                        [Dmitry]
- drm/bridge:
 1. use atomic_* callbacks.                           [Quentin]
 2. fix the incorrect formatting and spaces.
 3. add the required header files.                    [Dmitry]
 4. remove "enabled" flag.
 5. remove *fw from the lt7911exc struct.
 6. .max_register and .range_max use actual range.
 7. regulator use bulk interface.
 8. use dev_err_probe, devm_mutex_init and devm_drm_bridge_add.
 9. Replace GPL v2 with GPL.
- Link to v1: https://lore.kernel.org/lkml/20260420023354.1192642-1-syyang@lontium.com/

---
Sunyun Yang (2):
  dt-bindings: bridge: Add Lontium LT7911EXC eDP to MIPI DSI bridge
  drm/bridge: Add Lontium LT7911EXC eDP to MIPI DSI bridge

 .../display/bridge/lontium,lt7911exc.yaml     |  89 +++
 drivers/gpu/drm/bridge/Kconfig                |  15 +
 drivers/gpu/drm/bridge/Makefile               |   1 +
 drivers/gpu/drm/bridge/lontium-lt7911exc.c    | 642 ++++++++++++++++++
 4 files changed, 747 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/display/bridge/lontium,lt7911exc.yaml
 create mode 100644 drivers/gpu/drm/bridge/lontium-lt7911exc.c

-- 
2.34.1

Claude review: Add Lontium LT7911EXC eDP to MIPI DSI bridge

[Claude Code Review Bot]

Overall Series Review

Subject: Add Lontium LT7911EXC eDP to MIPI DSI bridge
Author: syyang@lontium.com
Patches: 3
Reviewed: 2026-05-16T09:43:27.762700

---

This is v8 of a 2-patch series adding a DRM bridge driver for the Lontium LT7911EXC, an eDP 1.4 to MIPI DSI converter. The DT binding (patch 1) already has a Reviewed-by from Krzysztof Kozlowski and looks clean. The driver (patch 2) has a Reviewed-by from Dmitry Baryshkov and follows the established pattern for bridge-chips-as-DSI-host (similar to tc358768, ssd2825), where `drm_bridge_add` is deferred to the DSI host attach callback.

The driver is generally well-structured for v8, but there are still several issues ranging from a real bug (sysfs version format truncation), unchecked error paths, unnecessary type widths, and some structural concerns around firmware upgrade safety.

---
Generated by Claude Code Patch Reviewer

[PATCH v7 0/2] Add Lontium LT7911EXC eDP to MIPI DSI bridge

[syyang]

From: Sunyun Yang <syyang@lontium.com>

The LT7911EXC is an I2C-controlled bridge that receives eDP1.4
and output mipi dsi. This series introduces:

- A device tree binding YAML file describing the hardware
- A new DRM bridge driver implementing the basic functionality

Signed-off-by: Sunyun Yang<syyang@lontium.com>
---
Change in v7:
- dt-binding:
 1. fix commit message typos(Receiver、signal)                            [sashiko-bot]
 2. remove the ambiguity caused by "signal/dual".
- drm/bridge:
 1. using devm_regulator_get_enable avoids power leaks.                   [sashiko-bot]
 2. set reset gpio is low after cutting off power in lt7911exc_remove function, avoid backpowering.
 3. synchronous request_firmware() call cause a permanent probe failure if the driver is built-in,
    probe executes before the root filesystem is mounted, which would cause this to fail with -ENOENT,
    we have removed this functionality. Use trigger to upgrade.
 4. add `depends on I2C` and `select REGMAP_I2C` in Kconfig.
 5. add return value of `devm_drm_bridge_add()` in `probe()`.
 6. add directly header files (linux/slab.h, linux/delay.h, linux/regulator/consumer.h)
- Link to v6: https://lore.kernel.org/lkml/20260508134702.4713-1-syyang@lontium.com/

Change in v6:
- dt-binding:
- drm/bridge:
 1. use #define FW_FILE  "Lontium/lt7911exc_fw.bin" to match linux-firmware
- Link to v5: https://lore.kernel.org/lkml/20260506013153.2240-1-syyang@lontium.com/

Change in v5:
- dt-binding:
- drm/bridge:
 1. Change "mipi" to "mipi dsi" in the commit message.     [Dmitry]
 2. Change "eDP/MIPI" to "eDP/MIPI DSI" in Kconfig.
- Link to v4: https://lore.kernel.org/lkml/20260430094612.3408174-1-syyang@lontium.com/

Change in v4:
- dt-binding:
 1. Fix the missing spaces on the "subject".             [Krzysztof]
 2. Fix the error descriptions for port@0 and port@1.
- drm/bridge:
- Link to v3: https://lore.kernel.org/lkml/20260429040541.3404116-1-syyang@lontium.com/

Change in v3:
- dt-binding:
- drm/bridge:
 1. already submit lt7911exc_fw.bin to linux-firmware.  [Dmitry]
 2. remove lt7911exc_remove function.
 3. drop  the "lontium, "  in lt7911exc_i2c_table.
- Link to v2: https://lore.kernel.org/lkml/20260428063224.3316655-1-syyang@lontium.com/

Change in v2:
- dt-binding:
 1. reset pins use active low.                        [Dmitry]
- drm/bridge:
 1. use atomic_* callbacks.                           [Quentin]
 2. fix the incorrect formatting and spaces.
 3. add the required header files.                    [Dmitry]
 4. remove "enabled" flag.
 5. remove *fw from the lt7911exc struct.
 6. .max_register and .range_max use actual range.
 7. regulator use bulk interface.
 8. use dev_err_probe, devm_mutex_init and devm_drm_bridge_add.
 9. Replace GPL v2 with GPL.
- Link to v1: https://lore.kernel.org/lkml/20260420023354.1192642-1-syyang@lontium.com/
---
Sunyun Yang (2):
  dt-bindings: bridge: Add Lontium LT7911EXC eDP to MIPI DSI bridge
  drm/bridge: Add Lontium LT7911EXC eDP to MIPI DSI bridge

 .../display/bridge/lontium,lt7911exc.yaml     |  89 +++
 drivers/gpu/drm/bridge/Kconfig                |  15 +
 drivers/gpu/drm/bridge/Makefile               |   1 +
 drivers/gpu/drm/bridge/lontium-lt7911exc.c    | 514 ++++++++++++++++++
 4 files changed, 619 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/display/bridge/lontium,lt7911exc.yaml
 create mode 100644 drivers/gpu/drm/bridge/lontium-lt7911exc.c

-- 
2.34.1

Claude review: Add Lontium LT7911EXC eDP to MIPI DSI bridge

[Claude Code Review Bot]

Overall Series Review

Subject: Add Lontium LT7911EXC eDP to MIPI DSI bridge
Author: syyang@lontium.com
Patches: 3
Reviewed: 2026-05-16T14:16:44.993415

---

This is a v7 2-patch series adding a Lontium LT7911EXC eDP-to-MIPI-DSI bridge driver. The DT binding (patch 1) has already been reviewed by Krzysztof Kozlowski and the driver (patch 2) by Dmitry Baryshkov.

The DT binding is clean and looks good. The driver has one **critical issue**: it uses atomic bridge callbacks (`atomic_pre_enable`, `atomic_disable`, `atomic_post_disable`) without providing the mandatory atomic state bookkeeping callbacks (`atomic_duplicate_state`, `atomic_destroy_state`, `atomic_reset`). All 40 other bridge drivers in the tree that use atomic callbacks provide these. Without `atomic_reset`, `drm_bridge_is_atomic()` returns false and the bridge private state object is never initialized, which can cause problems with the DRM atomic framework. Beyond that, there are several medium-severity issues around error handling, sysfs interface design, and unused includes.

The patches are also based on an older tree -- drm-next has since refactored the atomic bridge callback signatures from `struct drm_atomic_state *` to `struct drm_atomic_commit *`, so a rebase will be needed.

---

---
Generated by Claude Code Patch Reviewer

[PATCH v4 0/2] Add Lontium LT7911EXC eDP to MIPI DSI bridge

[syyang]

From: Sunyun Yang <syyang@lontium.com>

The LT7911EXC is an I2C-controlled bridge that Receiver eDP1.4
and output signal/dual port mipi. This series introduces:

- A device tree binding YAML file describing the hardware
- A new DRM bridge driver implementing the basic functionality

Signed-off-by: Sunyun Yang<syyang@lontium.com>
---
Change in v4:
- dt-binding:
 1. Fix the missing spaces on the "subject".             [Krzysztof]
 2. Fix the error descriptions for port@0 and port@1.
- drm/bridge:
- Link to v3: https://lore.kernel.org/lkml/20260429040541.3404116-1-syyang@lontium.com/

Change in v3:
- dt-binding:
- drm/bridge:
 1. already submit lt7911exc_fw.bin to linux-firmware.  [Dmitry]
 2. remove lt7911exc_remove function.
 3. drop  the "lontium, "  in lt7911exc_i2c_table.
- Link to v2: https://lore.kernel.org/lkml/20260428063224.3316655-1-syyang@lontium.com/

Change in v2:
- dt-binding:
 1. reset pins use active low.                        [Dmitry]
- drm/bridge:
 1. use atomic_* callbacks.                           [Quentin]
 2. fix the incorrect formatting and spaces.
 3. add the required header files.                    [Dmitry]
 4. remove "enabled" flag.
 5. remove *fw from the lt7911exc struct.
 6. .max_register and .range_max use actual range.
 7. regulator use bulk interface.
 8. use dev_err_probe, devm_mutex_init and devm_drm_bridge_add.
 9. Replace GPL v2 with GPL.
- Link to v1: https://lore.kernel.org/lkml/20260420023354.1192642-1-syyang@lontium.com/
---
Sunyun Yang (2):
  dt-bindings: bridge: Add Lontium LT7911EXC eDP to MIPI DSI bridge
  drm/bridge: Add Lontium LT7911EXC eDP to MIPI DSI bridge

 .../display/bridge/lontium,lt7911exc.yaml     |  89 ++++
 drivers/gpu/drm/bridge/Kconfig                |  13 +
 drivers/gpu/drm/bridge/Makefile               |   1 +
 drivers/gpu/drm/bridge/lontium-lt7911exc.c    | 493 ++++++++++++++++++
 4 files changed, 596 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/display/bridge/lontium,lt7911exc.yaml
 create mode 100644 drivers/gpu/drm/bridge/lontium-lt7911exc.c

-- 
2.34.1

Claude review: Add Lontium LT7911EXC eDP to MIPI DSI bridge

[Claude Code Review Bot]

Overall Series Review

Subject: Add Lontium LT7911EXC eDP to MIPI DSI bridge
Author: syyang@lontium.com
Patches: 4
Reviewed: 2026-05-05T10:47:37.467462

---

This is a v4 patch series adding a new DRM bridge driver for the Lontium LT7911EXC eDP-to-MIPI-DSI bridge chip. The binding patch (1/2) is reasonable but the driver patch (2/2) has several significant issues that need to be addressed before it can be merged:

1. **Missing mandatory atomic state helpers** — the driver uses atomic callbacks but does not provide `atomic_duplicate_state`, `atomic_destroy_state`, or `atomic_reset`, which are mandatory per the DRM bridge API contract.
2. **No MIPI DSI host attachment** — this is a bridge that outputs MIPI DSI, yet the driver never registers with or attaches to a DSI host. Every other Lontium bridge with DSI output (lt9611, lt9611uxc, lt8912b) does this. Without it, the bridge cannot actually drive a DSI panel/pipeline.
3. **Firmware upgrade runs synchronously in probe** — this blocks boot and could take a long time.
4. **Regulators left enabled on success path** after probe, wasting power until the display pipeline starts.
5. **Incomplete error handling** throughout the firmware flashing code.

The driver feels like an early skeleton that implements firmware flashing but is missing the core bridge functionality (mode detection, mode validation, DSI configuration).

---

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Generated by Claude Code Patch Reviewer