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

[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

[PATCH v7 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 straightforward and already has a Reviewed-by from Krzysztof Kozlowski. The binding looks correct.

**No issues found.** The binding properly describes the two ports (eDP input, DSI output), regulators (vdd 1.2V, vcc 3.3V), reset GPIO, and includes a complete example.

---

---
Generated by Claude Code Patch Reviewer

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

[syyang]

From: Sunyun Yang <syyang@lontium.com>

This commit adds support for the Lontium LT7911EXC eDP to MIPI DSI
bridge. It implements I2C-based setup, display configuration, and
provides a firmware update mechanism.

Signed-off-by: Sunyun Yang <syyang@lontium.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
---
 drivers/gpu/drm/bridge/Kconfig             |  15 +
 drivers/gpu/drm/bridge/Makefile            |   1 +
 drivers/gpu/drm/bridge/lontium-lt7911exc.c | 514 +++++++++++++++++++++
 3 files changed, 530 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..cb74730c6ef4 100644
--- a/drivers/gpu/drm/bridge/Kconfig
+++ b/drivers/gpu/drm/bridge/Kconfig
@@ -132,6 +132,21 @@ 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 FW_LOADER
+	select DRM_PANEL
+	select DRM_KMS_HELPER
+	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..ccea435b3c7b
--- /dev/null
+++ b/drivers/gpu/drm/bridge/lontium-lt7911exc.c
@@ -0,0 +1,514 @@
+// 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_bridge.h>
+#include <drm/drm_mipi_dsi.h>
+#include <drm/drm_of.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 {
+	struct device *dev;
+	struct i2c_client *client;
+	struct drm_bridge bridge;
+	struct regmap *regmap;
+	/* Protects all accesses to registers by stopping the on-chip MCU */
+	struct mutex ocm_lock;
+	struct gpio_desc *reset_gpio;
+	int fw_version;
+};
+
+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;
+
+	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 void lt7911exc_reset(struct lt7911exc *lt7911exc)
+{
+	gpiod_set_value_cansleep(lt7911exc->reset_gpio, 0);
+	msleep(20);
+
+	gpiod_set_value_cansleep(lt7911exc->reset_gpio, 1);
+	msleep(20);
+
+	gpiod_set_value_cansleep(lt7911exc->reset_gpio, 0);
+	msleep(400);
+
+	dev_dbg(lt7911exc->dev, "lt7911exc reset.\n");
+}
+
+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;
+
+	ret = regmap_write(lt7911exc->regmap, 0xe0ee, 0x01);
+	if (ret)
+		return ret;
+	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 void lt7911exc_lock(struct lt7911exc *lt7911exc)
+{
+	mutex_lock(&lt7911exc->ocm_lock);
+	regmap_write(lt7911exc->regmap, 0xe0ee, 0x01);
+}
+
+static void lt7911exc_unlock(struct lt7911exc *lt7911exc)
+{
+	regmap_write(lt7911exc->regmap, 0xe0ee, 0x00);
+	mutex_unlock(&lt7911exc->ocm_lock);
+}
+
+static void lt7911exc_block_erase(struct lt7911exc *lt7911exc)
+{
+	struct device *dev = lt7911exc->dev;
+	const u32 addr = 0x00;
+
+	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),
+	};
+
+	regmap_multi_reg_write(lt7911exc->regmap, seq_write, ARRAY_SIZE(seq_write));
+
+	msleep(200);
+	dev_dbg(dev, "erase flash done.\n");
+}
+
+static void lt7911exc_prog_init(struct lt7911exc *lt7911exc, u64 addr)
+{
+	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),
+	};
+
+	regmap_multi_reg_write(lt7911exc->regmap, seq_write, ARRAY_SIZE(seq_write));
+}
+
+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);
+		lt7911exc_prog_init(lt7911exc, addr);
+
+		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;
+	}
+
+	read_hw_crc = crc_tmp[0] << 24 | crc_tmp[1] << 16 |
+				crc_tmp[2] << 8 | 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 int lt7911exc_firmware_upgrade(struct lt7911exc *lt7911exc)
+{
+	struct device *dev = lt7911exc->dev;
+	const struct firmware *fw;
+	u8 *buffer;
+	size_t total_size = FW_SIZE - 4;
+	u32 crc32;
+	int ret;
+
+	/*1. load firmware*/
+	ret = request_firmware(&fw, FW_FILE, dev);
+	if (ret)
+		return dev_err_probe(dev, ret, "failed to load '%s'\n", FW_FILE);
+
+	/*2. check size*/
+	if (fw->size > total_size) {
+		dev_err(dev, "firmware too large (%zu > %zu)\n", fw->size, total_size);
+		ret = -EINVAL;
+		goto out_release_fw;
+	}
+
+	/*3. calculate crc32 */
+	buffer = kzalloc(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);
+	kfree(buffer);
+
+	/*4. firmware upgrade */
+	dev_dbg(dev, "starting firmware upgrade, size: %zu bytes\n", fw->size);
+
+	lt7911exc_block_erase(lt7911exc);
+
+	ret = lt7911exc_write_data(lt7911exc, fw, 0);
+	if (ret < 0) {
+		dev_err(dev, "failed to write firmware data\n");
+		goto out_release_fw;
+	}
+
+	ret = lt7911exc_write_crc(lt7911exc, crc32, FW_SIZE - 4);
+	if (ret < 0) {
+		dev_err(dev, "failed to write firmware crc\n");
+		goto out_release_fw;
+	}
+
+	/*5. check upgrade of result*/
+	lt7911exc_reset(lt7911exc);
+
+	ret = lt7911exc_upgrade_result(lt7911exc, crc32);
+
+out_release_fw:
+	release_firmware(fw);
+	return ret;
+}
+
+static void lt7911exc_atomic_pre_enable(struct drm_bridge *bridge, struct drm_atomic_state *state)
+{
+	struct lt7911exc *lt7911exc = bridge_to_lt7911exc(bridge);
+
+	lt7911exc_reset(lt7911exc);
+}
+
+static void lt7911exc_atomic_disable(struct drm_bridge *bridge, struct drm_atomic_state *state)
+{
+	/* Delay after panel is disabled */
+	msleep(20);
+}
+
+static void lt7911exc_atomic_post_disable(struct drm_bridge *bridge, struct drm_atomic_state *state)
+{
+	struct lt7911exc *lt7911exc = bridge_to_lt7911exc(bridge);
+
+	/* The reset GPIO is defined in device tree with GPIO_ACTIVE_LOW flag.
+	 * Set 1 means reset signal.
+	 */
+	gpiod_set_value_cansleep(lt7911exc->reset_gpio, 1);
+}
+
+static int lt7911exc_attach(struct drm_bridge *bridge,
+			    struct drm_encoder *encoder,
+			    enum drm_bridge_attach_flags flags)
+{
+	struct lt7911exc *lt7911exc = bridge_to_lt7911exc(bridge);
+
+	return drm_bridge_attach(lt7911exc->bridge.encoder, lt7911exc->bridge.next_bridge,
+				 &lt7911exc->bridge, flags);
+}
+
+static const struct drm_bridge_funcs lt7911exc_bridge_funcs = {
+	.attach = lt7911exc_attach,
+	.atomic_pre_enable = lt7911exc_atomic_pre_enable,
+	.atomic_disable = lt7911exc_atomic_disable,
+	.atomic_post_disable = lt7911exc_atomic_post_disable,
+};
+
+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);
+	int ret;
+
+	/* set 0: release reset signal */
+	gpiod_set_value_cansleep(lt7911exc->reset_gpio, 0);
+	msleep(400);
+
+	lt7911exc_lock(lt7911exc);
+
+	ret = lt7911exc_firmware_upgrade(lt7911exc);
+	if (ret < 0)
+		dev_err(dev, "upgrade failure\n");
+
+	lt7911exc->fw_version = lt7911exc_read_version(lt7911exc);
+
+	lt7911exc_unlock(lt7911exc);
+
+	return ret < 0 ? ret : len;
+}
+
+static ssize_t lt7911exc_firmware_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct lt7911exc *lt7911exc = dev_get_drvdata(dev);
+
+	return sysfs_emit(buf, "0x%04x\n", lt7911exc->fw_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 device *dev = &client->dev;
+	struct lt7911exc *lt7911exc;
+	int ret;
+
+	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");
+
+	lt7911exc->bridge.next_bridge = devm_drm_of_get_bridge(dev, dev->of_node, 1, 0);
+	if (IS_ERR(lt7911exc->bridge.next_bridge))
+		return PTR_ERR(lt7911exc->bridge.next_bridge);
+
+	lt7911exc->client = client;
+	lt7911exc->dev = dev;
+	i2c_set_clientdata(client, lt7911exc);
+
+	ret = devm_mutex_init(dev, &lt7911exc->ocm_lock);
+	if (ret)
+		return dev_err_probe(dev, ret, "failed to init mutex\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_LOW);
+	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);
+
+	lt7911exc_lock(lt7911exc);
+
+	lt7911exc->fw_version = lt7911exc_read_version(lt7911exc);
+
+	lt7911exc_unlock(lt7911exc);
+	if (lt7911exc->fw_version < 0)
+		return dev_err_probe(dev, lt7911exc->fw_version, "failed read version of chip\n");
+
+	lt7911exc->bridge.of_node = dev->of_node;
+
+	return devm_drm_bridge_add(dev, &lt7911exc->bridge);
+}
+
+static void lt7911exc_remove(struct i2c_client *client)
+{
+	struct lt7911exc *lt7911exc = i2c_get_clientdata(client);
+
+	/* pull reset low to prevent backpowering*/
+	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:**

1. **Missing atomic state management callbacks.** The driver uses `atomic_pre_enable`, `atomic_disable`, and `atomic_post_disable` but does not provide `atomic_duplicate_state`, `atomic_destroy_state`, or `atomic_reset`. The kernel documentation in `drm_bridge.c` explicitly states:

   > Bridge drivers may implement the legacy version of those operations, or the atomic version (prefixed with atomic_), in which case they shall also implement the atomic state bookkeeping operations (atomic_duplicate_state, atomic_destroy_state and reset).

   Without `atomic_reset`, `drm_bridge_is_atomic()` returns false and `drm_atomic_private_obj_init()` is never called during `drm_bridge_attach()`. Every other bridge driver in the tree using atomic callbacks provides these. The fix is to add the three helper functions, exactly as the sibling `lontium-lt9211.c` does:

   ```c
   .atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,
   .atomic_destroy_state   = drm_atomic_helper_bridge_destroy_state,
   .atomic_reset           = drm_atomic_helper_bridge_reset,
   ```

**Medium:**

2. **`lt7911exc_attach` uses `lt7911exc->bridge.encoder` instead of the `encoder` parameter.** While functionally equivalent (since `drm_bridge_attach` sets `bridge->encoder` before calling the callback), it's non-idiomatic and fragile:

   ```c
   return drm_bridge_attach(lt7911exc->bridge.encoder, lt7911exc->bridge.next_bridge,
                            &lt7911exc->bridge, flags);
   ```

   Should use `encoder` directly:
   ```c
   return drm_bridge_attach(encoder, lt7911exc->bridge.next_bridge,
                            &lt7911exc->bridge, flags);
   ```

3. **`lt7911exc_firmware_store` does not validate input.** The sysfs store callback ignores the buffer content entirely -- any write triggers a firmware upgrade. It should check for a specific trigger value (e.g., `"1\n"`) to prevent accidental upgrades.

4. **`lt7911exc_firmware_store` does not check `lt7911exc_read_version()` return value.** After firmware upgrade, the version is read but the error code is silently stored in `fw_version`:

   ```c
   lt7911exc->fw_version = lt7911exc_read_version(lt7911exc);
   ```

   If `lt7911exc_read_version` returns a negative error, subsequent reads from the `show` function would display a garbage version.

5. **`cal_crc32_custom` is unsafe for lengths not a multiple of 4.** The loop accesses `data[i+3]` without bounds checking. While the current caller always passes a length divisible by 4, the function itself is fragile. Either add a length check/assertion or document the requirement.

6. **Many register write return values are silently ignored.** `lt7911exc_block_erase`, `lt7911exc_prog_init`, `lt7911exc_lock`, `lt7911exc_unlock`, and `lt7911exc_write_crc` all ignore `regmap_write` / `regmap_multi_reg_write` return values. At minimum, `lt7911exc_block_erase` and `lt7911exc_prog_init` should propagate errors since they're part of the firmware upgrade path.

**Minor:**

7. **Kconfig help text formatting.** Missing space after period:

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

   Should be `chip. The LT7911EXC`.

8. **Unused include.** `#include <linux/platform_device.h>` is included but the driver is an I2C driver and never uses any platform_device APIs.

9. **Sysfs attribute naming.** `lt7911exc_firmware` embeds the driver name in the attribute name, which is unusual. Convention is a simple descriptive name like `firmware_version` (for the show) and `firmware_update` (for the store), or split into two attributes.

10. **`fw_version` format specifier.** `sysfs_emit(buf, "0x%04x\n", lt7911exc->fw_version)` uses `%04x` (4 hex digits, 16 bits), but the version is constructed from 3 bytes (24 bits). Should be `%06x` to consistently zero-pad the full version.

11. **`u64` used where `u32` suffices.** The `addr` parameter in `lt7911exc_prog_init`, `lt7911exc_write_data`, and `lt7911exc_write_crc` is `u64` but only 24 bits are ever used (3 bytes extracted). `u32` would be more appropriate.

12. **`lt7911exc_atomic_disable` is a bare delay.** The callback contains only `msleep(20)` with no hardware interaction. If this delay is truly needed, a comment explaining *why* (e.g., panel timing requirement) would help reviewers. If it's not needed, it should be removed.

---
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: 2026-05-16T14:16:44.993415

---

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 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

[PATCH v8 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 Krzysztof's Reviewed-by. No issues found.

---

---
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

[PATCH v4 1/2] dt-bindings: bridge: 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.

Signed-off-by: Sunyun Yang <syyang@lontium.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 in decent shape. Minor observations:

- **Missing `description` property at the top level**: The schema has `title` but no `description`. DT binding convention recommends a `description` block explaining the chip's capabilities (eDP 1.4 receiver, single/dual MIPI DSI output lanes, supported resolutions, etc.).

- **No `data-lanes` property for DSI output**: Since this chip supports "single/dual port MIPI" output, the binding should describe how the number of DSI lanes and ports is configured. Other MIPI DSI bridge bindings (e.g., `lontium,lt9611`) include `data-lanes` on the DSI port endpoints.

- **Commit message grammar**: "Receiver eDP1.4 and output signal/dual port mipi" — should be "receives eDP 1.4 input and outputs single/dual port MIPI DSI."

- **Example looks correct** — uses `GPIO_ACTIVE_LOW` for reset (matching the active-low convention), proper port definitions, correct I2C address.

Overall this patch is close but should add DSI lane configuration properties.

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Generated by Claude Code Patch Reviewer