On Fri, Jun 09, 2023 at 04:59:50PM +0200, Miquel Raynal wrote:
> This panel from Emerging Display Technologies Corporation features an
> ST7789V2 panel inside which is almost identical to what the Sitronix
> panel driver supports.
> 
> In practice, the module physical size is specific, and experiments show
> that the display will malfunction if any of the following situation
> occurs:
> * Pixel clock is above 3MHz
> * Pixel clock is not inverted
> I could not properly identify the reasons behind these failures, scope
> captures show valid input signals.
> 
> Signed-off-by: Miquel Raynal <miquel.ray...@bootlin.com>
> ---
>  .../gpu/drm/panel/panel-sitronix-st7789v.c    | 34 +++++++++++++++++--
>  1 file changed, 32 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panel/panel-sitronix-st7789v.c 
> b/drivers/gpu/drm/panel/panel-sitronix-st7789v.c
> index 212bccc31804..7de192a3a8aa 100644
> --- a/drivers/gpu/drm/panel/panel-sitronix-st7789v.c
> +++ b/drivers/gpu/drm/panel/panel-sitronix-st7789v.c
> @@ -30,7 +30,8 @@
>  #define ST7789V_RGBCTRL_RCM(n)                       (((n) & 3) << 5)
>  #define ST7789V_RGBCTRL_VSYNC_HIGH           BIT(3)
>  #define ST7789V_RGBCTRL_HSYNC_HIGH           BIT(2)
> -#define ST7789V_RGBCTRL_PCLK_HIGH            BIT(1)
> +#define ST7789V_RGBCTRL_PCLK_FALLING         BIT(1)
> +#define ST7789V_RGBCTRL_PCLK_RISING          0
>  #define ST7789V_RGBCTRL_VBP(n)                       ((n) & 0x7f)
>  #define ST7789V_RGBCTRL_HBP(n)                       ((n) & 0x1f)
>  
> @@ -117,6 +118,7 @@ struct st7789v_panel_info {
>       u16 width_mm;
>       u16 height_mm;
>       u32 bus_format;
> +     u32 bus_flags;
>  };
>  
>  struct st7789v {
> @@ -175,6 +177,18 @@ static const struct drm_display_mode default_mode = {
>       .vtotal = 320 + 8 + 4 + 4,
>  };
>  
> +static const struct drm_display_mode slow_mode = {
> +     .clock = 3000,
> +     .hdisplay = 240,
> +     .hsync_start = 240 + 38,
> +     .hsync_end = 240 + 38 + 10,
> +     .htotal = 240 + 38 + 10 + 10,
> +     .vdisplay = 320,
> +     .vsync_start = 320 + 8,
> +     .vsync_end = 320 + 8 + 4,
> +     .vtotal = 320 + 8 + 4 + 4,
> +};

Why is it supposed to be slow (and compared to what)? It looks like a
fairly normal mode to me? Or is it because it's refreshed at 30Hz?

Either way, the ST7789V is a panel controller and can be connected to a
wide range of panels depending on the model, so it would be better to
just use the model name there.

>  static int st7789v_get_modes(struct drm_panel *panel,
>                            struct drm_connector *connector)
>  {
> @@ -197,6 +211,7 @@ static int st7789v_get_modes(struct drm_panel *panel,
>  
>       connector->display_info.width_mm = panel_info->width_mm;
>       connector->display_info.height_mm = panel_info->height_mm;
> +     connector->display_info.bus_flags = panel_info->bus_flags;
>       drm_display_info_set_bus_formats(&connector->display_info,
>                                        &panel_info->bus_format, 1);
>  
> @@ -206,8 +221,13 @@ static int st7789v_get_modes(struct drm_panel *panel,
>  static int st7789v_prepare(struct drm_panel *panel)
>  {
>       struct st7789v *ctx = panel_to_st7789v(panel);
> +     const struct st7789v_panel_info *panel_info = ctx->panel_info;
> +     u8 pck = ST7789V_RGBCTRL_PCLK_FALLING;
>       int ret;
>  
> +     if (panel_info->bus_flags & DRM_BUS_FLAG_PIXDATA_SAMPLE_POSEDGE)
> +             pck = ST7789V_RGBCTRL_PCLK_RISING;
> +

I guess it could be in a separate commit

Maxime

>       ret = regulator_enable(ctx->power);
>       if (ret)
>               return ret;
> @@ -321,7 +341,7 @@ static int st7789v_prepare(struct drm_panel *panel)
>                                            ST7789V_RGBCTRL_RCM(2) |
>                                            ST7789V_RGBCTRL_VSYNC_HIGH |
>                                            ST7789V_RGBCTRL_HSYNC_HIGH |
> -                                          ST7789V_RGBCTRL_PCLK_HIGH));
> +                                          pck));
>       ST7789V_TEST(ret, st7789v_write_data(ctx, ST7789V_RGBCTRL_VBP(8)));
>       ST7789V_TEST(ret, st7789v_write_data(ctx, ST7789V_RGBCTRL_HBP(20)));
>  
> @@ -422,14 +442,24 @@ static const struct st7789v_panel_info st7789v_info = {
>       .bus_format = MEDIA_BUS_FMT_RGB666_1X18,
>  };
>  
> +static const struct st7789v_panel_info et028013dma_info = {
> +     .display_mode = &slow_mode,
> +     .width_mm = 43,
> +     .height_mm = 58,
> +     .bus_format = MEDIA_BUS_FMT_RGB666_1X18,
> +     .bus_flags = DRM_BUS_FLAG_PIXDATA_SAMPLE_POSEDGE,
> +};
> +
>  static const struct of_device_id st7789v_of_match[] = {
>       { .compatible = "sitronix,st7789v", .data = &st7789v_info },
> +     { .compatible = "edt,et028013dma", .data = &et028013dma_info },

We should sort them by alphabetical order

Maxime

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