[PATCH v4 0/2] drm/panel: Add panel driver for ChipWealth CH13726A based panels

[PATCH v4 0/2] drm/panel: Add panel driver for ChipWealth CH13726A based panels

[Aaron Kling via B4 Relay]

This driver is based on the one by Teguh Sobirin [0], cut down to only
support the AYN Thor bottom panel.

Due to [1], the AYN vendor description patch has been folded into the
AYN QCS8550 dt series. Which means this series now depends on said
series and it must be picked up before this.

[0] https://github.com/AYNTechnologies/linux/commit/d0ff75b09e66023c5f88992706dee4601aa7a437
[1] https://lore.kernel.org/linux-arm-msm/c7fb3f89-6574-4761-9ef2-2fdf6d4801b5@kernel.org

Signed-off-by: Aaron Kling <webgeek1234@gmail.com>
---
Changes in v4:
- Add fallback compatible to bindings doc in patch 1
- Link to v3: https://lore.kernel.org/r/20260323-ch13726a-v3-0-e28b6f97fe80@gmail.com

Changes in v3:
- Reword patch 1 commit message for clarity
- Order properties properly in patch 1
- Track vendor description dependency series change
- Link to v2: https://lore.kernel.org/r/20260317-ch13726a-v2-0-28aa46bcd6d0@gmail.com

Changes in v2:
- Add Neil Armstrong to binding maintainer list
- Add 120hz mode, which required a minor restructure of the driver
- Link to v1: https://lore.kernel.org/r/20260222-ch13726a-v1-0-e501d78e105a@gmail.com

---
Aaron Kling (1):
      dt-bindings: display: panel: Add ChipWealth CH13726A AMOLED driver

Teguh Sobirin (1):
      drm/panel: Add panel driver for ChipWealth CH13726A based panels

 .../display/panel/chipwealth,ch13726a.yaml         |  67 ++++
 drivers/gpu/drm/panel/Kconfig                      |  11 +
 drivers/gpu/drm/panel/Makefile                     |   1 +
 drivers/gpu/drm/panel/panel-chipwealth-ch13726a.c  | 339 +++++++++++++++++++++
 4 files changed, 418 insertions(+)
---
base-commit: 785f0eb2f85decbe7c1ef9ae922931f0194ffc2e
change-id: 20260220-ch13726a-59c6678d53d8
prerequisite-change-id: 20260217-ayn-qcs8550-16c07b63de26:v4
prerequisite-patch-id: 042cab8f04748207ba5395dd0f23c445955aaa2b
prerequisite-patch-id: 4e13275bfaa4f838a627fe8dfa3d4cb8972fc5b4
prerequisite-patch-id: 16c130bcfd7c787b91e828b8e600bd0d740f937e
prerequisite-patch-id: 4b7e6b017349c386f54e221790da4392fe066ff3
prerequisite-patch-id: 3844bef2eda3cf59031b1d131eb6ba9295629bb4
prerequisite-patch-id: bcb261e40f0386b91a09eb4080cbdf74d21f3df2

Best regards,
-- 
Aaron Kling <webgeek1234@gmail.com>

[PATCH v4 1/2] dt-bindings: display: panel: Add ChipWealth CH13726A AMOLED driver

[Aaron Kling via B4 Relay]

From: Aaron Kling <webgeek1234@gmail.com>

The Chip Wealth Technology CH13726A AMOLED driver is a single chip
solution for MIPI-DSI. This is used for the AYN Thor bottom panel.

Signed-off-by: Aaron Kling <webgeek1234@gmail.com>
---
 .../display/panel/chipwealth,ch13726a.yaml         | 67 ++++++++++++++++++++++
 1 file changed, 67 insertions(+)

diff --git a/Documentation/devicetree/bindings/display/panel/chipwealth,ch13726a.yaml b/Documentation/devicetree/bindings/display/panel/chipwealth,ch13726a.yaml
new file mode 100644
index 00000000000000..c8d7b61037e622
--- /dev/null
+++ b/Documentation/devicetree/bindings/display/panel/chipwealth,ch13726a.yaml
@@ -0,0 +1,67 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/display/panel/chipwealth,ch13726a.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Chip Wealth Technology CH13726A AMOLED driver
+
+maintainers:
+  - Neil Armstrong <neil.armstrong@linaro.org>
+
+description:
+  Chip Wealth Technology CH13726A is a single-chip solution
+  for AMOLED connected using a MIPI-DSI video interface.
+
+allOf:
+  - $ref: panel-common.yaml#
+
+properties:
+  compatible:
+    items:
+      - const: ayntec,thor-panel-bottom
+      - const: chipwealth,ch13726a
+
+  reg:
+    maxItems: 1
+    description: DSI virtual channel
+
+  vdd-supply: true
+  vddio-supply: true
+  vdd1v2-supply: true
+  avdd-supply: true
+
+  port: true
+  reset-gpios: true
+  rotation: true
+
+required:
+  - compatible
+  - reg
+  - vdd-supply
+  - vddio-supply
+  - vdd1v2-supply
+  - avdd-supply
+  - reset-gpios
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+
+    dsi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+        panel@0 {
+            compatible = "ayntec,thor-panel-bottom", "chipwealth,ch13726a";
+            reg = <0>;
+            vdd1v2-supply = <&vreg_l11b_1p2>;
+            vddio-supply = <&vdd_disp_1v8>;
+            vdd-supply = <&vreg_l13b_3p0>;
+            avdd-supply = <&vdd_disp2_2v8>;
+            reset-gpios = <&tlmm 133 GPIO_ACTIVE_HIGH>;
+        };
+    };
+
+...

-- 
2.53.0

Re: [PATCH v4 1/2] dt-bindings: display: panel: Add ChipWealth CH13726A AMOLED driver

[Krzysztof Kozlowski]

On Wed, Apr 08, 2026 at 12:32:39AM -0500, Aaron Kling wrote:
> The Chip Wealth Technology CH13726A AMOLED driver is a single chip
> solution for MIPI-DSI. This is used for the AYN Thor bottom panel.
> 
> Signed-off-by: Aaron Kling <webgeek1234@gmail.com>
> ---
>  .../display/panel/chipwealth,ch13726a.yaml         | 67 ++++++++++++++++++++++
>  1 file changed, 67 insertions(+)

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>

Best regards,
Krzysztof

Claude review: dt-bindings: display: panel: Add ChipWealth CH13726A AMOLED driver

[Claude Code Review Bot]

Patch Review

This patch looks good overall.

**Minor observations:**

- The binding correctly uses a two-entry compatible (`"ayntec,thor-panel-bottom"`, `"chipwealth,ch13726a"`) which was requested in v4 changes.

- The `port` property is listed as `true` but not in `required`. This is fine since the DSI connection will be described by the parent node, but it might be worth documenting that it's optional if board-specific DTS needs vary.

- No issues with the supply names, reset-gpios, or the example.

**Verdict:** Looks ready to merge.

---

---
Generated by Claude Code Patch Reviewer

[PATCH v4 2/2] drm/panel: Add panel driver for ChipWealth CH13726A based panels

[Aaron Kling via B4 Relay]

From: Teguh Sobirin <teguh@sobir.in>

This is used by the AYN Thor for the bottom panel.

Signed-off-by: Teguh Sobirin <teguh@sobir.in>
Co-developed-by: Aaron Kling <webgeek1234@gmail.com>
Signed-off-by: Aaron Kling <webgeek1234@gmail.com>
---
 drivers/gpu/drm/panel/Kconfig                     |  11 +
 drivers/gpu/drm/panel/Makefile                    |   1 +
 drivers/gpu/drm/panel/panel-chipwealth-ch13726a.c | 339 ++++++++++++++++++++++
 3 files changed, 351 insertions(+)

diff --git a/drivers/gpu/drm/panel/Kconfig b/drivers/gpu/drm/panel/Kconfig
index d6863b28ddc559..e2c00f08f4507d 100644
--- a/drivers/gpu/drm/panel/Kconfig
+++ b/drivers/gpu/drm/panel/Kconfig
@@ -105,6 +105,17 @@ config DRM_PANEL_BOE_TV101WUM_LL2
 	  Say Y here if you want to support for BOE TV101WUM-LL2
 	  WUXGA PANEL DSI Video Mode panel
 
+config DRM_PANEL_CHIPWEALTH_CH13726A
+	tristate "CHIPWEALTH CH13726A-based DSI panel"
+	depends on OF
+	depends on DRM_MIPI_DSI
+	depends on BACKLIGHT_CLASS_DEVICE
+	select DRM_DISPLAY_DP_HELPER
+	select DRM_DISPLAY_HELPER
+	help
+	  Say Y here if you want to enable support for ChipWealth
+	  CH13726A-based display panels.
+
 config DRM_PANEL_EBBG_FT8719
 	tristate "EBBG FT8719 panel driver"
 	depends on OF
diff --git a/drivers/gpu/drm/panel/Makefile b/drivers/gpu/drm/panel/Makefile
index a4291dc3905bed..343d283d1620fb 100644
--- a/drivers/gpu/drm/panel/Makefile
+++ b/drivers/gpu/drm/panel/Makefile
@@ -9,6 +9,7 @@ obj-$(CONFIG_DRM_PANEL_BOE_TD4320) += panel-boe-td4320.o
 obj-$(CONFIG_DRM_PANEL_BOE_TH101MB31UIG002_28A) += panel-boe-th101mb31ig002-28a.o
 obj-$(CONFIG_DRM_PANEL_BOE_TV101WUM_LL2) += panel-boe-tv101wum-ll2.o
 obj-$(CONFIG_DRM_PANEL_BOE_TV101WUM_NL6) += panel-boe-tv101wum-nl6.o
+obj-$(CONFIG_DRM_PANEL_CHIPWEALTH_CH13726A) += panel-chipwealth-ch13726a.o
 obj-$(CONFIG_DRM_PANEL_DSI_CM) += panel-dsi-cm.o
 obj-$(CONFIG_DRM_PANEL_LVDS) += panel-lvds.o
 obj-$(CONFIG_DRM_PANEL_SIMPLE) += panel-simple.o
diff --git a/drivers/gpu/drm/panel/panel-chipwealth-ch13726a.c b/drivers/gpu/drm/panel/panel-chipwealth-ch13726a.c
new file mode 100644
index 00000000000000..48a5e20e07c487
--- /dev/null
+++ b/drivers/gpu/drm/panel/panel-chipwealth-ch13726a.c
@@ -0,0 +1,339 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * ChipWealth CH13726A MIPI-DSI panel driver
+ * Copyright (c) 2024, Teguh Sobirin <teguh@sobir.in>.
+ */
+
+#include <linux/backlight.h>
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/regulator/consumer.h>
+
+#include <drm/drm_mipi_dsi.h>
+#include <drm/drm_modes.h>
+#include <drm/drm_panel.h>
+
+#include <video/mipi_display.h>
+
+struct ch13726a_panel {
+	struct drm_panel panel;
+	struct mipi_dsi_device *dsi;
+	struct regulator_bulk_data supplies[4];
+	struct gpio_desc *reset_gpio;
+	struct ch13726a_desc *desc;
+	enum drm_panel_orientation orientation;
+	bool prepared;
+};
+
+struct ch13726a_desc {
+	unsigned int width_mm;
+	unsigned int height_mm;
+	unsigned int bpc;
+
+	const struct drm_display_mode *modes;
+	unsigned int num_modes;
+};
+
+static inline struct ch13726a_panel *to_ch13726a_panel(struct drm_panel *panel)
+{
+	return container_of(panel, struct ch13726a_panel, panel);
+}
+
+static void ch13726a_reset(struct ch13726a_panel *ctx)
+{
+	gpiod_set_value_cansleep(ctx->reset_gpio, 1);
+	usleep_range(10000, 11000);
+	gpiod_set_value_cansleep(ctx->reset_gpio, 0);
+	usleep_range(10000, 11000);
+	gpiod_set_value_cansleep(ctx->reset_gpio, 1);
+	usleep_range(10000, 11000);
+}
+
+static int ch13726a_on(struct ch13726a_panel *ctx)
+{
+	struct mipi_dsi_multi_context dsi_ctx = { .dsi = ctx->dsi };
+
+	ctx->dsi->mode_flags |= MIPI_DSI_MODE_LPM;
+
+	mipi_dsi_generic_write_seq_multi(&dsi_ctx, 0xf0, 0x50);
+	mipi_dsi_generic_write_seq_multi(&dsi_ctx, 0xb9, 0x00);
+
+	mipi_dsi_dcs_exit_sleep_mode_multi(&dsi_ctx);
+
+	mipi_dsi_dcs_set_display_on_multi(&dsi_ctx);
+
+	return dsi_ctx.accum_err;
+}
+
+static int ch13726a_disable(struct drm_panel *panel)
+{
+	struct ch13726a_panel *ctx = to_ch13726a_panel(panel);
+	struct mipi_dsi_multi_context dsi_ctx = { .dsi = ctx->dsi };
+
+	ctx->dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
+
+	mipi_dsi_dcs_set_display_off_multi(&dsi_ctx);
+	mipi_dsi_msleep(&dsi_ctx, 50);
+	mipi_dsi_dcs_enter_sleep_mode_multi(&dsi_ctx);
+
+	return dsi_ctx.accum_err;
+}
+
+static int ch13726a_prepare(struct drm_panel *panel)
+{
+	struct ch13726a_panel *ctx = to_ch13726a_panel(panel);
+	struct device *dev = &ctx->dsi->dev;
+	int ret;
+
+	if (ctx->prepared)
+		return 0;
+
+	ret = regulator_bulk_enable(ARRAY_SIZE(ctx->supplies), ctx->supplies);
+	if (ret < 0) {
+		dev_err(dev, "Failed to enable regulators: %d\n", ret);
+		return ret;
+	}
+
+	ch13726a_reset(ctx);
+
+	ret = ch13726a_on(ctx);
+	if (ret < 0) {
+		dev_err(dev, "Failed to initialize panel: %d\n", ret);
+		gpiod_set_value_cansleep(ctx->reset_gpio, 0);
+		regulator_bulk_disable(ARRAY_SIZE(ctx->supplies), ctx->supplies);
+		return ret;
+	}
+
+	msleep(28);
+
+	ctx->prepared = true;
+
+	return 0;
+}
+
+static int ch13726a_unprepare(struct drm_panel *panel)
+{
+	struct ch13726a_panel *ctx = to_ch13726a_panel(panel);
+
+	if (!ctx->prepared)
+		return 0;
+
+	gpiod_set_value_cansleep(ctx->reset_gpio, 0);
+	regulator_bulk_disable(ARRAY_SIZE(ctx->supplies), ctx->supplies);
+
+	ctx->prepared = false;
+	return 0;
+}
+
+static const struct drm_display_mode thor_bottom_modes[] = {
+	{
+		/* 120Hz */
+		.clock = (1080 + 28 + 4 + 36) * (1240 + 16 + 4 + 8) * 120 / 1000,
+		.hdisplay = 1080,
+		.hsync_start = 1080 + 28,
+		.hsync_end = 1080 + 28 + 4,
+		.htotal = 1080 + 28 + 4 + 36,
+		.vdisplay = 1240,
+		.vsync_start = 1240 + 16,
+		.vsync_end = 1240 + 16 + 4,
+		.vtotal = 1240 + 16 + 4 + 8,
+	},
+	{
+		/* 60Hz */
+		.clock = (1080 + 28 + 4 + 36) * (1240 + 16 + 4 + 8) * 60 / 1000,
+		.hdisplay = 1080,
+		.hsync_start = 1080 + 28,
+		.hsync_end = 1080 + 28 + 4,
+		.htotal = 1080 + 28 + 4 + 36,
+		.vdisplay = 1240,
+		.vsync_start = 1240 + 16,
+		.vsync_end = 1240 + 16 + 4,
+		.vtotal = 1240 + 16 + 4 + 8,
+	}
+};
+
+static struct ch13726a_desc thor_bottom_desc = {
+	.modes = thor_bottom_modes,
+	.num_modes = ARRAY_SIZE(thor_bottom_modes),
+	.width_mm = 65,
+	.height_mm = 75,
+	.bpc = 8,
+};
+
+static int ch13726a_get_modes(struct drm_panel *panel,
+					struct drm_connector *connector)
+{
+	struct ch13726a_panel *ctx = to_ch13726a_panel(panel);
+
+	for (uint8_t i = 0; i < ctx->desc->num_modes; i++) {
+		const struct drm_display_mode *m = &ctx->desc->modes[i];
+		struct drm_display_mode *mode;
+
+		mode = drm_mode_duplicate(connector->dev, m);
+		if (!mode) {
+			dev_err(&ctx->dsi->dev, "failed to add mode %ux%u@%u\n",
+				m->hdisplay, m->vdisplay, drm_mode_vrefresh(m));
+			return -ENOMEM;
+		}
+
+		mode->type = DRM_MODE_TYPE_DRIVER;
+		if (i == 0)
+			mode->type |= DRM_MODE_TYPE_PREFERRED;
+
+		drm_mode_set_name(mode);
+		drm_mode_probed_add(connector, mode);
+	}
+
+	connector->display_info.width_mm = ctx->desc->width_mm;
+	connector->display_info.height_mm = ctx->desc->height_mm;
+	connector->display_info.bpc = ctx->desc->bpc;
+
+	return ctx->desc->num_modes;
+}
+
+static enum drm_panel_orientation ch13726a_get_orientation(struct drm_panel *panel)
+{
+	struct ch13726a_panel *ctx = to_ch13726a_panel(panel);
+
+	return ctx->orientation;
+}
+
+static const struct drm_panel_funcs ch13726a_panel_funcs = {
+	.prepare = ch13726a_prepare,
+	.unprepare = ch13726a_unprepare,
+	.disable = ch13726a_disable,
+	.get_modes = ch13726a_get_modes,
+	.get_orientation = ch13726a_get_orientation,
+};
+
+static int ch13726a_bl_update_status(struct backlight_device *bl)
+{
+	struct mipi_dsi_device *dsi = bl_get_data(bl);
+	u16 brightness = backlight_get_brightness(bl);
+	int ret;
+
+	dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
+
+	ret = mipi_dsi_dcs_set_display_brightness(dsi, brightness);
+	if (ret < 0)
+		return ret;
+
+	dsi->mode_flags |= MIPI_DSI_MODE_LPM;
+
+	return 0;
+}
+
+static const struct backlight_ops ch13726a_bl_ops = {
+	.update_status = ch13726a_bl_update_status,
+};
+
+static struct backlight_device *
+ch13726a_create_backlight(struct mipi_dsi_device *dsi)
+{
+	struct device *dev = &dsi->dev;
+	const struct backlight_properties props = {
+		.type = BACKLIGHT_RAW,
+		.brightness = 255,
+		.max_brightness = 255,
+	};
+
+	return devm_backlight_device_register(dev, dev_name(dev), dev, dsi,
+					      &ch13726a_bl_ops, &props);
+}
+
+static int ch13726a_probe(struct mipi_dsi_device *dsi)
+{
+	struct device *dev = &dsi->dev;
+	struct ch13726a_panel *ctx;
+	int ret;
+
+	ctx = devm_kzalloc(dev, sizeof(*ctx), GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+
+	ctx->desc = (struct ch13726a_desc *)of_device_get_match_data(dev);
+	if (!ctx->desc)
+		return -ENODEV;
+
+	ctx->supplies[0].supply = "vdd1v2";
+	ctx->supplies[1].supply = "vddio";
+	ctx->supplies[2].supply = "vdd";
+	ctx->supplies[3].supply = "avdd";
+
+	ret = devm_regulator_bulk_get(dev, ARRAY_SIZE(ctx->supplies),
+				      ctx->supplies);
+	if (ret < 0)
+		return dev_err_probe(dev, ret, "Failed to get regulators\n");
+
+	ctx->reset_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
+	if (IS_ERR(ctx->reset_gpio))
+		return dev_err_probe(dev, PTR_ERR(ctx->reset_gpio),
+				     "Failed to get reset-gpios\n");
+
+	ret = of_drm_get_panel_orientation(dev->of_node, &ctx->orientation);
+	if (ret < 0) {
+		dev_err(dev, "%pOF: failed to get orientation %d\n", dev->of_node, ret);
+		return ret;
+	}
+
+	ctx->dsi = dsi;
+	mipi_dsi_set_drvdata(dsi, ctx);
+
+	dsi->lanes = 4;
+	dsi->format = MIPI_DSI_FMT_RGB888;
+	dsi->mode_flags = MIPI_DSI_MODE_VIDEO |
+			  MIPI_DSI_CLOCK_NON_CONTINUOUS;
+
+	drm_panel_init(&ctx->panel, dev, &ch13726a_panel_funcs,
+		       DRM_MODE_CONNECTOR_DSI);
+	ctx->panel.prepare_prev_first = true;
+
+	ctx->panel.backlight = ch13726a_create_backlight(dsi);
+	if (IS_ERR(ctx->panel.backlight))
+		return dev_err_probe(dev, PTR_ERR(ctx->panel.backlight),
+				     "Failed to create backlight\n");
+
+	drm_panel_add(&ctx->panel);
+
+	ret = mipi_dsi_attach(dsi);
+	if (ret < 0) {
+		dev_err(dev, "Failed to attach to DSI host: %d\n", ret);
+		drm_panel_remove(&ctx->panel);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void ch13726a_remove(struct mipi_dsi_device *dsi)
+{
+	struct ch13726a_panel *ctx = mipi_dsi_get_drvdata(dsi);
+	int ret;
+
+	ret = mipi_dsi_detach(dsi);
+	if (ret < 0)
+		dev_err(&dsi->dev, "Failed to detach from DSI host: %d\n", ret);
+
+	drm_panel_remove(&ctx->panel);
+}
+
+static const struct of_device_id ch13726a_of_match[] = {
+	{ .compatible = "ayntec,thor-panel-bottom", .data = &thor_bottom_desc },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, ch13726a_of_match);
+
+static struct mipi_dsi_driver ch13726a_driver = {
+	.probe = ch13726a_probe,
+	.remove = ch13726a_remove,
+	.driver = {
+		.name = "panel-ch13726a-amoled",
+		.of_match_table = ch13726a_of_match,
+	},
+};
+module_mipi_dsi_driver(ch13726a_driver);
+
+MODULE_DESCRIPTION("DRM driver for CH13726A DSI panels");
+MODULE_LICENSE("GPL");

-- 
2.53.0

Claude review: drm/panel: Add panel driver for ChipWealth CH13726A based panels

[Claude Code Review Bot]

Patch Review

Several issues need attention:

**1. Unnecessary `select DRM_DISPLAY_DP_HELPER` and `select DRM_DISPLAY_HELPER` in Kconfig (important)**

```c
+	select DRM_DISPLAY_DP_HELPER
+	select DRM_DISPLAY_HELPER
```

This is a pure MIPI-DSI panel driver — it has no DisplayPort or DSC functionality. These selects are unnecessary and pull in code the driver doesn't use. Other pure MIPI-DSI panel drivers (e.g., `panel-boe-th101mb31ig002-28a`, `panel-himax-hx8394`) do not select these. Remove both lines.

**2. Redundant `prepared` flag tracking (important)**

```c
+struct ch13726a_panel {
+	...
+	bool prepared;
+};
```

And in `ch13726a_prepare()`:

```c
+	if (ctx->prepared)
+		return 0;
+	...
+	ctx->prepared = true;
```

And in `ch13726a_unprepare()`:

```c
+	if (!ctx->prepared)
+		return 0;
+	...
+	ctx->prepared = false;
```

The DRM panel core already tracks `panel->prepared` and guards against double-prepare/unprepare in `drm_panel_prepare()`/`drm_panel_unprepare()` (see `drm_panel.c` lines 122-134 and 177-199). This driver-level tracking is redundant and should be removed. No current in-tree panel driver uses a private `prepared` flag anymore.

**3. `thor_bottom_desc` should be `const` (minor)**

```c
+static struct ch13726a_desc thor_bottom_desc = {
```

This should be `static const struct ch13726a_desc`. It's immutable data. The struct member should also be `const`:

```c
-	struct ch13726a_desc *desc;
+	const struct ch13726a_desc *desc;
```

This would also eliminate the need for the cast in probe:

```c
+	ctx->desc = (struct ch13726a_desc *)of_device_get_match_data(dev);
```

With `const struct ch13726a_desc *desc`, this becomes simply:

```c
	ctx->desc = of_device_get_match_data(dev);
```

**4. `uint8_t` loop variable (minor, style)**

```c
+	for (uint8_t i = 0; i < ctx->desc->num_modes; i++) {
```

Kernel code uses `u8` rather than `uint8_t`, but for a loop index iterating over a small count, a plain `unsigned int` or `int` is more idiomatic. Declaring the variable inside `for()` is a C99/C11 feature — while it works with modern kernel builds, many panel drivers still declare loop variables at function scope. Use `int i;` declared at the top for consistency with the prevailing kernel style.

**5. Reset GPIO polarity in error path (worth verifying)**

In `ch13726a_prepare()`:

```c
+		gpiod_set_value_cansleep(ctx->reset_gpio, 0);
```

The GPIO is obtained with `GPIOD_OUT_LOW` and the reset sequence asserts high (1), deasserts to low (0), then asserts high (1) again. In the error path after `ch13726a_on()` fails, the driver sets GPIO to 0 (deasserted/inactive), which keeps the panel out of reset. This is inconsistent — typically on error you want to put the panel *into* reset (assert reset) before disabling regulators. If active-high means "reset active", the error path should set the GPIO to 1. However, this depends on the actual hardware semantics. Since the binding says `GPIO_ACTIVE_HIGH` and `reset-gpios` is the name, `gpiod_set_value(1)` means "assert reset" which would be the safer state on error. Worth confirming with the hardware.

Similarly in `ch13726a_unprepare()`:

```c
+	gpiod_set_value_cansleep(ctx->reset_gpio, 0);
```

This deasserts reset before killing power, which could leave the panel in an undefined state. Most panel drivers assert reset (set to 1) before cutting regulators to ensure clean shutdown. Compare with how `ch13726a_reset()` works — it uses `1` as the active/working state. The unprepare should logically assert reset (1) then cut power, not the other way around.

**6. `mipi_dsi_detach` error checking in `remove()` is unnecessary noise (very minor)**

```c
+	ret = mipi_dsi_detach(dsi);
+	if (ret < 0)
+		dev_err(&dsi->dev, "Failed to detach from DSI host: %d\n", ret);
```

`mipi_dsi_detach()` never fails in practice (the host ops->detach can return an error, but no upstream host driver does). Newer panel drivers tend to not check this return. Not a blocker, but the error message adds no value.

**7. Missing `msleep`/delay between display-off and sleep-enter in `ch13726a_disable()` (minor)**

```c
+	mipi_dsi_dcs_set_display_off_multi(&dsi_ctx);
+	mipi_dsi_msleep(&dsi_ctx, 50);
+	mipi_dsi_dcs_enter_sleep_mode_multi(&dsi_ctx);
```

There is a 50ms delay between display-off and sleep-enter, which is good. But there is no delay *after* entering sleep mode. Many MIPI panel datasheets require a delay (commonly 120ms) after entering sleep mode before cutting power in `unprepare()`. The `ch13726a_on()` path has a 28ms `msleep` at the end of `prepare()`, but the disable->unprepare transition has no such guard. If the panel requires a post-sleep delay per its datasheet, this could cause issues.

**8. Mode flags manipulation in backlight callback (worth noting)**

```c
+static int ch13726a_bl_update_status(struct backlight_device *bl)
+{
+	...
+	dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
+	ret = mipi_dsi_dcs_set_display_brightness(dsi, brightness);
+	...
+	dsi->mode_flags |= MIPI_DSI_MODE_LPM;
```

And in `ch13726a_on()`:

```c
+	ctx->dsi->mode_flags |= MIPI_DSI_MODE_LPM;
```

And `ch13726a_disable()`:

```c
+	ctx->dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
```

The LPM flag toggling is not protected by any locking. If backlight updates can race with disable/prepare calls, the mode_flags could be corrupted. This is a pre-existing pattern in many panel drivers, so not unique to this one, but worth noting.

**Summary of requested changes for v5:**
1. Remove `DRM_DISPLAY_DP_HELPER` and `DRM_DISPLAY_HELPER` from Kconfig
2. Remove the private `prepared` bool and the associated checks
3. Make `thor_bottom_desc` and the `desc` pointer `const`, drop the cast
4. Use `int` or `unsigned int` for the loop variable, not `uint8_t`
5. Verify GPIO reset polarity in error/unprepare paths (assert reset before cutting power)

---
Generated by Claude Code Patch Reviewer

Claude review: drm/panel: Add panel driver for ChipWealth CH13726A based panels

[Claude Code Review Bot]

Overall Series Review

Subject: drm/panel: Add panel driver for ChipWealth CH13726A based panels
Author: Aaron Kling via B4 Relay <devnull+webgeek1234.gmail.com@kernel.org>
Patches: 4
Reviewed: 2026-04-12T13:10:38.270464

---

This is a straightforward 2-patch series adding a new MIPI-DSI panel driver for the ChipWealth CH13726A AMOLED, used as the bottom panel on the AYN Thor handheld device. The dt-bindings patch is clean and well-structured. The driver patch is functional but has several issues ranging from unnecessary boilerplate (redundant `prepared` tracking that the core already handles) to a potentially incorrect Kconfig (selecting DP helpers for a pure DSI panel) and minor style issues. None are critical, but a v5 addressing them would be worthwhile.

---

---
Generated by Claude Code Patch Reviewer

[PATCH v3 0/2] drm/panel: Add panel driver for ChipWealth CH13726A based panels

[Aaron Kling via B4 Relay]

This driver is based on the one by Teguh Sobirin [0], cut down to only
support the AYN Thor bottom panel.

Due to [1], the AYN vendor description patch has been folded into the
AYN QCS8550 dt series. Which means this series now depends on said
series and it must be picked up before this.

[0] https://github.com/AYNTechnologies/linux/commit/d0ff75b09e66023c5f88992706dee4601aa7a437
[1] https://lore.kernel.org/linux-arm-msm/c7fb3f89-6574-4761-9ef2-2fdf6d4801b5@kernel.org

Signed-off-by: Aaron Kling <webgeek1234@gmail.com>
---
Changes in v3:
- Reword patch 1 commit message for clarity
- Order properties properly in patch 1
- Track vendor description dependency series change
- Link to v2: https://lore.kernel.org/r/20260317-ch13726a-v2-0-28aa46bcd6d0@gmail.com

Changes in v2:
- Add Neil Armstrong to binding maintainer list
- Add 120hz mode, which required a minor restructure of the driver
- Link to v1: https://lore.kernel.org/r/20260222-ch13726a-v1-0-e501d78e105a@gmail.com

---
Aaron Kling (1):
      dt-bindings: display: panel: Add ChipWealth CH13726A AMOLED driver

Teguh Sobirin (1):
      drm/panel: Add panel driver for ChipWealth CH13726A based panels

 .../display/panel/chipwealth,ch13726a.yaml         |  65 ++++
 drivers/gpu/drm/panel/Kconfig                      |  11 +
 drivers/gpu/drm/panel/Makefile                     |   1 +
 drivers/gpu/drm/panel/panel-chipwealth-ch13726a.c  | 339 +++++++++++++++++++++
 4 files changed, 416 insertions(+)
---
base-commit: 785f0eb2f85decbe7c1ef9ae922931f0194ffc2e
change-id: 20260220-ch13726a-59c6678d53d8
prerequisite-change-id: 20260217-ayn-qcs8550-16c07b63de26:v4
prerequisite-patch-id: 042cab8f04748207ba5395dd0f23c445955aaa2b
prerequisite-patch-id: 4e13275bfaa4f838a627fe8dfa3d4cb8972fc5b4
prerequisite-patch-id: 16c130bcfd7c787b91e828b8e600bd0d740f937e
prerequisite-patch-id: 4b7e6b017349c386f54e221790da4392fe066ff3
prerequisite-patch-id: 3844bef2eda3cf59031b1d131eb6ba9295629bb4
prerequisite-patch-id: bcb261e40f0386b91a09eb4080cbdf74d21f3df2

Best regards,
-- 
Aaron Kling <webgeek1234@gmail.com>

[PATCH v3 2/2] drm/panel: Add panel driver for ChipWealth CH13726A based panels

[Aaron Kling via B4 Relay]

From: Teguh Sobirin <teguh@sobir.in>

This is used by the AYN Thor for the bottom panel.

Signed-off-by: Teguh Sobirin <teguh@sobir.in>
Co-developed-by: Aaron Kling <webgeek1234@gmail.com>
Signed-off-by: Aaron Kling <webgeek1234@gmail.com>
---
 drivers/gpu/drm/panel/Kconfig                     |  11 +
 drivers/gpu/drm/panel/Makefile                    |   1 +
 drivers/gpu/drm/panel/panel-chipwealth-ch13726a.c | 339 ++++++++++++++++++++++
 3 files changed, 351 insertions(+)

diff --git a/drivers/gpu/drm/panel/Kconfig b/drivers/gpu/drm/panel/Kconfig
index a99f2e2a49fe66a09c6f2d503f570b05a5e228b1..e953b61a819082866b93d0a453ee750a76d70c18 100644
--- a/drivers/gpu/drm/panel/Kconfig
+++ b/drivers/gpu/drm/panel/Kconfig
@@ -105,6 +105,17 @@ config DRM_PANEL_BOE_TV101WUM_LL2
 	  Say Y here if you want to support for BOE TV101WUM-LL2
 	  WUXGA PANEL DSI Video Mode panel
 
+config DRM_PANEL_CHIPWEALTH_CH13726A
+	tristate "CHIPWEALTH CH13726A-based DSI panel"
+	depends on OF
+	depends on DRM_MIPI_DSI
+	depends on BACKLIGHT_CLASS_DEVICE
+	select DRM_DISPLAY_DP_HELPER
+	select DRM_DISPLAY_HELPER
+	help
+	  Say Y here if you want to enable support for ChipWealth
+	  CH13726A-based display panels.
+
 config DRM_PANEL_EBBG_FT8719
 	tristate "EBBG FT8719 panel driver"
 	depends on OF
diff --git a/drivers/gpu/drm/panel/Makefile b/drivers/gpu/drm/panel/Makefile
index 3336a2c0cd86419b6a22f74dcde6df966a311da9..85da2eb5a5c664d4302837f52e7e10ec11da8966 100644
--- a/drivers/gpu/drm/panel/Makefile
+++ b/drivers/gpu/drm/panel/Makefile
@@ -9,6 +9,7 @@ obj-$(CONFIG_DRM_PANEL_BOE_TD4320) += panel-boe-td4320.o
 obj-$(CONFIG_DRM_PANEL_BOE_TH101MB31UIG002_28A) += panel-boe-th101mb31ig002-28a.o
 obj-$(CONFIG_DRM_PANEL_BOE_TV101WUM_LL2) += panel-boe-tv101wum-ll2.o
 obj-$(CONFIG_DRM_PANEL_BOE_TV101WUM_NL6) += panel-boe-tv101wum-nl6.o
+obj-$(CONFIG_DRM_PANEL_CHIPWEALTH_CH13726A) += panel-chipwealth-ch13726a.o
 obj-$(CONFIG_DRM_PANEL_DSI_CM) += panel-dsi-cm.o
 obj-$(CONFIG_DRM_PANEL_LVDS) += panel-lvds.o
 obj-$(CONFIG_DRM_PANEL_SIMPLE) += panel-simple.o
diff --git a/drivers/gpu/drm/panel/panel-chipwealth-ch13726a.c b/drivers/gpu/drm/panel/panel-chipwealth-ch13726a.c
new file mode 100644
index 0000000000000000000000000000000000000000..48a5e20e07c48748e073f8bb9147036c18c51caa
--- /dev/null
+++ b/drivers/gpu/drm/panel/panel-chipwealth-ch13726a.c
@@ -0,0 +1,339 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * ChipWealth CH13726A MIPI-DSI panel driver
+ * Copyright (c) 2024, Teguh Sobirin <teguh@sobir.in>.
+ */
+
+#include <linux/backlight.h>
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/regulator/consumer.h>
+
+#include <drm/drm_mipi_dsi.h>
+#include <drm/drm_modes.h>
+#include <drm/drm_panel.h>
+
+#include <video/mipi_display.h>
+
+struct ch13726a_panel {
+	struct drm_panel panel;
+	struct mipi_dsi_device *dsi;
+	struct regulator_bulk_data supplies[4];
+	struct gpio_desc *reset_gpio;
+	struct ch13726a_desc *desc;
+	enum drm_panel_orientation orientation;
+	bool prepared;
+};
+
+struct ch13726a_desc {
+	unsigned int width_mm;
+	unsigned int height_mm;
+	unsigned int bpc;
+
+	const struct drm_display_mode *modes;
+	unsigned int num_modes;
+};
+
+static inline struct ch13726a_panel *to_ch13726a_panel(struct drm_panel *panel)
+{
+	return container_of(panel, struct ch13726a_panel, panel);
+}
+
+static void ch13726a_reset(struct ch13726a_panel *ctx)
+{
+	gpiod_set_value_cansleep(ctx->reset_gpio, 1);
+	usleep_range(10000, 11000);
+	gpiod_set_value_cansleep(ctx->reset_gpio, 0);
+	usleep_range(10000, 11000);
+	gpiod_set_value_cansleep(ctx->reset_gpio, 1);
+	usleep_range(10000, 11000);
+}
+
+static int ch13726a_on(struct ch13726a_panel *ctx)
+{
+	struct mipi_dsi_multi_context dsi_ctx = { .dsi = ctx->dsi };
+
+	ctx->dsi->mode_flags |= MIPI_DSI_MODE_LPM;
+
+	mipi_dsi_generic_write_seq_multi(&dsi_ctx, 0xf0, 0x50);
+	mipi_dsi_generic_write_seq_multi(&dsi_ctx, 0xb9, 0x00);
+
+	mipi_dsi_dcs_exit_sleep_mode_multi(&dsi_ctx);
+
+	mipi_dsi_dcs_set_display_on_multi(&dsi_ctx);
+
+	return dsi_ctx.accum_err;
+}
+
+static int ch13726a_disable(struct drm_panel *panel)
+{
+	struct ch13726a_panel *ctx = to_ch13726a_panel(panel);
+	struct mipi_dsi_multi_context dsi_ctx = { .dsi = ctx->dsi };
+
+	ctx->dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
+
+	mipi_dsi_dcs_set_display_off_multi(&dsi_ctx);
+	mipi_dsi_msleep(&dsi_ctx, 50);
+	mipi_dsi_dcs_enter_sleep_mode_multi(&dsi_ctx);
+
+	return dsi_ctx.accum_err;
+}
+
+static int ch13726a_prepare(struct drm_panel *panel)
+{
+	struct ch13726a_panel *ctx = to_ch13726a_panel(panel);
+	struct device *dev = &ctx->dsi->dev;
+	int ret;
+
+	if (ctx->prepared)
+		return 0;
+
+	ret = regulator_bulk_enable(ARRAY_SIZE(ctx->supplies), ctx->supplies);
+	if (ret < 0) {
+		dev_err(dev, "Failed to enable regulators: %d\n", ret);
+		return ret;
+	}
+
+	ch13726a_reset(ctx);
+
+	ret = ch13726a_on(ctx);
+	if (ret < 0) {
+		dev_err(dev, "Failed to initialize panel: %d\n", ret);
+		gpiod_set_value_cansleep(ctx->reset_gpio, 0);
+		regulator_bulk_disable(ARRAY_SIZE(ctx->supplies), ctx->supplies);
+		return ret;
+	}
+
+	msleep(28);
+
+	ctx->prepared = true;
+
+	return 0;
+}
+
+static int ch13726a_unprepare(struct drm_panel *panel)
+{
+	struct ch13726a_panel *ctx = to_ch13726a_panel(panel);
+
+	if (!ctx->prepared)
+		return 0;
+
+	gpiod_set_value_cansleep(ctx->reset_gpio, 0);
+	regulator_bulk_disable(ARRAY_SIZE(ctx->supplies), ctx->supplies);
+
+	ctx->prepared = false;
+	return 0;
+}
+
+static const struct drm_display_mode thor_bottom_modes[] = {
+	{
+		/* 120Hz */
+		.clock = (1080 + 28 + 4 + 36) * (1240 + 16 + 4 + 8) * 120 / 1000,
+		.hdisplay = 1080,
+		.hsync_start = 1080 + 28,
+		.hsync_end = 1080 + 28 + 4,
+		.htotal = 1080 + 28 + 4 + 36,
+		.vdisplay = 1240,
+		.vsync_start = 1240 + 16,
+		.vsync_end = 1240 + 16 + 4,
+		.vtotal = 1240 + 16 + 4 + 8,
+	},
+	{
+		/* 60Hz */
+		.clock = (1080 + 28 + 4 + 36) * (1240 + 16 + 4 + 8) * 60 / 1000,
+		.hdisplay = 1080,
+		.hsync_start = 1080 + 28,
+		.hsync_end = 1080 + 28 + 4,
+		.htotal = 1080 + 28 + 4 + 36,
+		.vdisplay = 1240,
+		.vsync_start = 1240 + 16,
+		.vsync_end = 1240 + 16 + 4,
+		.vtotal = 1240 + 16 + 4 + 8,
+	}
+};
+
+static struct ch13726a_desc thor_bottom_desc = {
+	.modes = thor_bottom_modes,
+	.num_modes = ARRAY_SIZE(thor_bottom_modes),
+	.width_mm = 65,
+	.height_mm = 75,
+	.bpc = 8,
+};
+
+static int ch13726a_get_modes(struct drm_panel *panel,
+					struct drm_connector *connector)
+{
+	struct ch13726a_panel *ctx = to_ch13726a_panel(panel);
+
+	for (uint8_t i = 0; i < ctx->desc->num_modes; i++) {
+		const struct drm_display_mode *m = &ctx->desc->modes[i];
+		struct drm_display_mode *mode;
+
+		mode = drm_mode_duplicate(connector->dev, m);
+		if (!mode) {
+			dev_err(&ctx->dsi->dev, "failed to add mode %ux%u@%u\n",
+				m->hdisplay, m->vdisplay, drm_mode_vrefresh(m));
+			return -ENOMEM;
+		}
+
+		mode->type = DRM_MODE_TYPE_DRIVER;
+		if (i == 0)
+			mode->type |= DRM_MODE_TYPE_PREFERRED;
+
+		drm_mode_set_name(mode);
+		drm_mode_probed_add(connector, mode);
+	}
+
+	connector->display_info.width_mm = ctx->desc->width_mm;
+	connector->display_info.height_mm = ctx->desc->height_mm;
+	connector->display_info.bpc = ctx->desc->bpc;
+
+	return ctx->desc->num_modes;
+}
+
+static enum drm_panel_orientation ch13726a_get_orientation(struct drm_panel *panel)
+{
+	struct ch13726a_panel *ctx = to_ch13726a_panel(panel);
+
+	return ctx->orientation;
+}
+
+static const struct drm_panel_funcs ch13726a_panel_funcs = {
+	.prepare = ch13726a_prepare,
+	.unprepare = ch13726a_unprepare,
+	.disable = ch13726a_disable,
+	.get_modes = ch13726a_get_modes,
+	.get_orientation = ch13726a_get_orientation,
+};
+
+static int ch13726a_bl_update_status(struct backlight_device *bl)
+{
+	struct mipi_dsi_device *dsi = bl_get_data(bl);
+	u16 brightness = backlight_get_brightness(bl);
+	int ret;
+
+	dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
+
+	ret = mipi_dsi_dcs_set_display_brightness(dsi, brightness);
+	if (ret < 0)
+		return ret;
+
+	dsi->mode_flags |= MIPI_DSI_MODE_LPM;
+
+	return 0;
+}
+
+static const struct backlight_ops ch13726a_bl_ops = {
+	.update_status = ch13726a_bl_update_status,
+};
+
+static struct backlight_device *
+ch13726a_create_backlight(struct mipi_dsi_device *dsi)
+{
+	struct device *dev = &dsi->dev;
+	const struct backlight_properties props = {
+		.type = BACKLIGHT_RAW,
+		.brightness = 255,
+		.max_brightness = 255,
+	};
+
+	return devm_backlight_device_register(dev, dev_name(dev), dev, dsi,
+					      &ch13726a_bl_ops, &props);
+}
+
+static int ch13726a_probe(struct mipi_dsi_device *dsi)
+{
+	struct device *dev = &dsi->dev;
+	struct ch13726a_panel *ctx;
+	int ret;
+
+	ctx = devm_kzalloc(dev, sizeof(*ctx), GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+
+	ctx->desc = (struct ch13726a_desc *)of_device_get_match_data(dev);
+	if (!ctx->desc)
+		return -ENODEV;
+
+	ctx->supplies[0].supply = "vdd1v2";
+	ctx->supplies[1].supply = "vddio";
+	ctx->supplies[2].supply = "vdd";
+	ctx->supplies[3].supply = "avdd";
+
+	ret = devm_regulator_bulk_get(dev, ARRAY_SIZE(ctx->supplies),
+				      ctx->supplies);
+	if (ret < 0)
+		return dev_err_probe(dev, ret, "Failed to get regulators\n");
+
+	ctx->reset_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
+	if (IS_ERR(ctx->reset_gpio))
+		return dev_err_probe(dev, PTR_ERR(ctx->reset_gpio),
+				     "Failed to get reset-gpios\n");
+
+	ret = of_drm_get_panel_orientation(dev->of_node, &ctx->orientation);
+	if (ret < 0) {
+		dev_err(dev, "%pOF: failed to get orientation %d\n", dev->of_node, ret);
+		return ret;
+	}
+
+	ctx->dsi = dsi;
+	mipi_dsi_set_drvdata(dsi, ctx);
+
+	dsi->lanes = 4;
+	dsi->format = MIPI_DSI_FMT_RGB888;
+	dsi->mode_flags = MIPI_DSI_MODE_VIDEO |
+			  MIPI_DSI_CLOCK_NON_CONTINUOUS;
+
+	drm_panel_init(&ctx->panel, dev, &ch13726a_panel_funcs,
+		       DRM_MODE_CONNECTOR_DSI);
+	ctx->panel.prepare_prev_first = true;
+
+	ctx->panel.backlight = ch13726a_create_backlight(dsi);
+	if (IS_ERR(ctx->panel.backlight))
+		return dev_err_probe(dev, PTR_ERR(ctx->panel.backlight),
+				     "Failed to create backlight\n");
+
+	drm_panel_add(&ctx->panel);
+
+	ret = mipi_dsi_attach(dsi);
+	if (ret < 0) {
+		dev_err(dev, "Failed to attach to DSI host: %d\n", ret);
+		drm_panel_remove(&ctx->panel);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void ch13726a_remove(struct mipi_dsi_device *dsi)
+{
+	struct ch13726a_panel *ctx = mipi_dsi_get_drvdata(dsi);
+	int ret;
+
+	ret = mipi_dsi_detach(dsi);
+	if (ret < 0)
+		dev_err(&dsi->dev, "Failed to detach from DSI host: %d\n", ret);
+
+	drm_panel_remove(&ctx->panel);
+}
+
+static const struct of_device_id ch13726a_of_match[] = {
+	{ .compatible = "ayntec,thor-panel-bottom", .data = &thor_bottom_desc },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, ch13726a_of_match);
+
+static struct mipi_dsi_driver ch13726a_driver = {
+	.probe = ch13726a_probe,
+	.remove = ch13726a_remove,
+	.driver = {
+		.name = "panel-ch13726a-amoled",
+		.of_match_table = ch13726a_of_match,
+	},
+};
+module_mipi_dsi_driver(ch13726a_driver);
+
+MODULE_DESCRIPTION("DRM driver for CH13726A DSI panels");
+MODULE_LICENSE("GPL");

-- 
2.53.0

Claude review: drm/panel: Add panel driver for ChipWealth CH13726A based panels

[Claude Code Review Bot]

Patch Review

Several issues:

1. **Unnecessary and incorrect Kconfig selects.** The Kconfig entry selects `DRM_DISPLAY_DP_HELPER` and `DRM_DISPLAY_HELPER`:

```
+	select DRM_DISPLAY_DP_HELPER
+	select DRM_DISPLAY_HELPER
```

This is a MIPI-DSI panel, not a DisplayPort panel. The driver doesn't use any DP helpers. These selects should be removed entirely — no replacement is needed since `drm_mipi_dsi.h` and `drm_panel.h` don't depend on them.

2. **`prepared` flag is deprecated.** The driver manually tracks `prepared` state:

```c
+	bool prepared;
```

```c
+	if (ctx->prepared)
+		return 0;
```

The DRM panel framework has handled prepare/unprepare idempotency since commit work in recent kernels. Only 2 legacy drivers in the tree still use this pattern. Remove the `prepared` field and the guard checks in `ch13726a_prepare()` and `ch13726a_unprepare()`.

3. **`of_device_get_match_data()` cast drops const.** The probe function casts away const:

```c
+	ctx->desc = (struct ch13726a_desc *)of_device_get_match_data(dev);
```

The `desc` field in the struct should be `const struct ch13726a_desc *desc` and the cast removed. Similarly, `thor_bottom_desc` should be `static const`:

```c
+static struct ch13726a_desc thor_bottom_desc = {
```

Should be `static const struct ch13726a_desc thor_bottom_desc`.

4. **`uint8_t` is not kernel style.** The kernel uses `u8` not `uint8_t`:

```c
+	for (uint8_t i = 0; i < ctx->desc->num_modes; i++) {
```

Should use `unsigned int i` (since `num_modes` is `unsigned int` and the value is small, there's no reason to use `u8` here anyway).

5. **Reset GPIO polarity may be inverted.** The reset sequence does high-low-high:

```c
+	gpiod_set_value_cansleep(ctx->reset_gpio, 1);
+	usleep_range(10000, 11000);
+	gpiod_set_value_cansleep(ctx->reset_gpio, 0);
+	usleep_range(10000, 11000);
+	gpiod_set_value_cansleep(ctx->reset_gpio, 1);
```

The GPIO is obtained with `GPIOD_OUT_LOW` (meaning initially deasserted). Typically a reset is assert-deassert (1-0-1 asserts then deasserts), but the dt-binding example uses `GPIO_ACTIVE_HIGH`, which means `gpiod_set_value(1)` drives the pin high. This is plausible for an active-high reset, but worth confirming the hardware — most AMOLED panels use active-low reset where the sequence would be 0-1-0 (assert low, release high). If the GPIO is active-high reset, then the unprepare path sets reset to 0 (deasserted/released), which means the panel leaves reset deasserted during power-down — that's backwards. Usually you want to assert reset *before* cutting power.

6. **`ch13726a_disable()` clears `MIPI_DSI_MODE_LPM` but `ch13726a_on()` sets it.** In `ch13726a_disable()`:

```c
+	ctx->dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
```

This means the display-off and sleep-enter commands are sent in HS mode, but the init sequence sends commands in LP mode. This is fine if intentional, but the backlight handler also toggles LPM:

```c
+	dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
+	ret = mipi_dsi_dcs_set_display_brightness(dsi, brightness);
+	...
+	dsi->mode_flags |= MIPI_DSI_MODE_LPM;
```

Toggling `mode_flags` like this is racy if backlight updates can happen concurrently with enable/disable. Consider setting the mode flags once in probe and not toggling them per-operation.

7. **Missing `#include <linux/of.h>` guard.** The driver includes `<linux/of.h>` but could use `<linux/mod_devicetable.h>` instead for `of_device_id`, matching newer driver conventions (see `panel-boe-td4320.c`). Minor style point.

8. **`ch13726a_remove()` error check on detach is unnecessary boilerplate.** `mipi_dsi_detach()` return value logging in remove is acceptable but some maintainers prefer to just ignore it since there's nothing useful to do with the error in the remove path.

---
Generated by Claude Code Patch Reviewer

Claude review: drm/panel: Add panel driver for ChipWealth CH13726A based panels

[Claude Code Review Bot]

Overall Series Review

Subject: drm/panel: Add panel driver for ChipWealth CH13726A based panels
Author: Aaron Kling via B4 Relay <devnull+webgeek1234.gmail.com@kernel.org>
Patches: 5
Reviewed: 2026-03-25T07:40:21.203030

---

This is a v3 series adding a new MIPI-DSI panel driver for the ChipWealth CH13726A, used in the AYN Thor handheld's bottom panel. The series is 2 patches: a dt-binding YAML and the panel driver itself. The driver is straightforward and mostly follows current conventions, but there are several issues ranging from an incorrect Kconfig select to deprecated patterns that should be addressed.

---
Generated by Claude Code Patch Reviewer