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

[Aaron Kling]

On Mon, Apr 13, 2026 at 4:17 AM Neil Armstrong
<neil.armstrong@xxxxxxxxxx> wrote:
>
> On 4/8/26 07:32, Aaron Kling via B4 Relay wrote:
> > From: Teguh Sobirin <teguh@xxxxxxxx>
> >
> > This is used by the AYN Thor for the bottom panel.
> >
> > Signed-off-by: Teguh Sobirin <teguh@xxxxxxxx>
> > Co-developed-by: Aaron Kling <webgeek1234@xxxxxxxxx>
> > Signed-off-by: Aaron Kling <webgeek1234@xxxxxxxxx>
> > ---
> >   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@xxxxxxxx>.
> > + */
> > +
> > +#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;
>
> Drop this, it's handled by the panel core now.
Ack.
>
> > +};
> > +
> > +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;
> > +             }
>
> Can you use drm_connector_helper_get_modes_fixed instead ?

Per the description for that function, it only works if there's a
single mode. This panel supports two modes, 60hz and 120hz.
>
> > +
> > +             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");
> > +
> Can you switch to devm_regulator_bulk_get_const ?

Looks like I can.
>
> > +     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);
>
> Please use devm_drm_panel_alloc() instead.

Ack
>
> > +     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");
> >
>
Aaron