Re: [PATCH v6 07/42] drm/mediatek: mtk_dpi: Add support for DPI input clock from HDMI

[CK Hu (胡俊光)]

On Tue, 2025-02-11 at 12:33 +0100, AngeloGioacchino Del Regno wrote:
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> 
> 
> On some SoCs, like MT8195 and MT8188, the DPI instance that is
> reserved to the HDMI Transmitter uses a different clock topology.
> 
> In this case, the DPI is clocked by the HDMI IP, and this outputs
> its clock to the MM input of dpi_pixel_clk, which is essential to
> enable register access to the DPI IP.
> 
> Add a `clocked_by_hdmi` member to struct mtk_dpi_conf, and check
> it to avoid enabling the DPI clocks in the mediatek-drm internal
> .start() callback (and avoid disabing in the .stop() component
> callback): this will make sure that the clock configuration
> sequence is respected during display pipeline setup by following
> the bridge ops between DPI and HDMI, where the HDMI driver is
> expected to enable the clocks in the bridge's pre_enable(), and
> DPI in the enable() cb.
> 
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/mediatek/mtk_dpi.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dpi.c b/drivers/gpu/drm/mediatek/mtk_dpi.c
> index ad07005ad56e..6493c7e2fae4 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dpi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dpi.c
> @@ -146,6 +146,8 @@ struct mtk_dpi_factor {
>   * @input_2p_en_bit: Enable bit of two pixel per round feature
>   * @pixels_per_iter: Quantity of transferred pixels per iteration.
>   * @edge_cfg_in_mmsys: If the edge configuration for DPI's output needs to be set in MMSYS.
> + * @clocked_by_hdmi: HDMI IP outputs clock to dpi_pixel_clk input clock, needed
> + *                  for DPI registers access.
>   */
>  struct mtk_dpi_conf {
>         const struct mtk_dpi_factor *dpi_factor;
> @@ -167,6 +169,7 @@ struct mtk_dpi_conf {
>         u32 input_2p_en_bit;
>         u32 pixels_per_iter;
>         bool edge_cfg_in_mmsys;
> +       bool clocked_by_hdmi;
>  };
> 
>  static void mtk_dpi_mask(struct mtk_dpi *dpi, u32 offset, u32 val, u32 mask)
> @@ -587,7 +590,9 @@ static int mtk_dpi_set_display_mode(struct mtk_dpi *dpi,
>         struct videomode vm = { 0 };
> 
>         drm_display_mode_to_videomode(mode, &vm);
> -       mtk_dpi_set_pixel_clk(dpi, &vm, mode->clock);
> +
> +       if (!dpi->conf->clocked_by_hdmi)
> +               mtk_dpi_set_pixel_clk(dpi, &vm, mode->clock);
> 
>         dpi_pol.ck_pol = MTK_DPI_POLARITY_FALLING;
>         dpi_pol.de_pol = MTK_DPI_POLARITY_RISING;
> @@ -922,14 +927,16 @@ void mtk_dpi_start(struct device *dev)
>  {
>         struct mtk_dpi *dpi = dev_get_drvdata(dev);
> 
> -       mtk_dpi_power_on(dpi);
> +       if (!dpi->conf->clocked_by_hdmi)
> +               mtk_dpi_power_on(dpi);

mtk_dpi_bridge_enable() also call mtk_dpi_power_on().
Add this checking in mtk_dpi_bridge_enable() also.

>  }
> 
>  void mtk_dpi_stop(struct device *dev)
>  {
>         struct mtk_dpi *dpi = dev_get_drvdata(dev);
> 
> -       mtk_dpi_power_off(dpi);
> +       if (!dpi->conf->clocked_by_hdmi)
> +               mtk_dpi_power_off(dpi);

mtk_dpi_bridge_disable() also call mtk_dpi_power_off().
Add this checking in mtk_dpi_bridge_disable() also.

Because the clock is from hdmi, I think the clock define in DPI node in device tree should be removed.
Also change the binding document and let the clock not required in MT8195.

Regards,
CK

>  }
> 
>  unsigned int mtk_dpi_encoder_index(struct device *dev)
> --
> 2.48.1
>