Re: [PATCH v4 4/7] drm/rcar-du: dsi: Support DSC in the pipeline

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Tomi,

Thank you for the patch.

On Mon, Jun 15, 2026 at 09:28:09AM +0300, Tomi Valkeinen wrote:
> Enabling DSI clocks on rcar-du needs some tricks as the DU dot clock is
> provided by the DSI. Thus, we call rcar_mipi_dsi_pclk_enable() from the
> crtc, when enabling the crtc.
> 
> With DSC (added in upcoming patch) in the pipeline, between the DU and
> the DSI, the above call path is broken as the crtc tries to call
> rcar_mipi_dsi_pclk_enable() on the DSC.
> 
> To solve this problem, add checks to rcar_du_crtc_atomic_enable() and
> rcar_du_crtc_atomic_disable() to detect the DSC via the bridge type, and
> skip the DCS bridge when needed.
> 
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>
> ---
>  drivers/gpu/drm/renesas/rcar-du/rcar_du_crtc.c  | 18 ++++++++++++++++++
>  drivers/gpu/drm/renesas/rcar-du/rcar_mipi_dsi.c |  1 +
>  2 files changed, 19 insertions(+)
> 
> diff --git a/drivers/gpu/drm/renesas/rcar-du/rcar_du_crtc.c b/drivers/gpu/drm/renesas/rcar-du/rcar_du_crtc.c
> index 6c07c406f725..f14fd89f9104 100644
> --- a/drivers/gpu/drm/renesas/rcar-du/rcar_du_crtc.c
> +++ b/drivers/gpu/drm/renesas/rcar-du/rcar_du_crtc.c
> @@ -754,6 +754,15 @@ static void rcar_du_crtc_atomic_enable(struct drm_crtc *crtc,
>  	     (BIT(RCAR_DU_OUTPUT_DSI0) | BIT(RCAR_DU_OUTPUT_DSI1)))) {
>  		struct drm_bridge *bridge = rcdu->dsi[rcrtc->index];
>  
> +		/*
> +		 * When we have a DSC block between the DU and the DSI,
> +		 * the "bridge" points to the DSC. Detect the DSC by looking
> +		 * at the bridge type, and skip the DSC if the bridge is not
> +		 * the DSI bridge.
> +		 */
> +		if (bridge->type != DRM_MODE_CONNECTOR_DSI)
> +			bridge = bridge->next_bridge;
> +

Is there a reason you don't do this in rcar_du_encoder_init() instead ?
It would avoid running this code on every enable/disable.

>  		rcar_mipi_dsi_pclk_enable(bridge, state);
>  	}
>  
> @@ -796,6 +805,15 @@ static void rcar_du_crtc_atomic_disable(struct drm_crtc *crtc,
>  	     (BIT(RCAR_DU_OUTPUT_DSI0) | BIT(RCAR_DU_OUTPUT_DSI1)))) {
>  		struct drm_bridge *bridge = rcdu->dsi[rcrtc->index];
>  
> +		/*
> +		 * When we have a DSC block between the DU and the DSI,
> +		 * the "bridge" points to the DSC. Detect the DSC by looking
> +		 * at the bridge type, and skip the DSC if the bridge is not
> +		 * the DSI bridge.
> +		 */
> +		if (bridge->type != DRM_MODE_CONNECTOR_DSI)
> +			bridge = bridge->next_bridge;
> +
>  		/*
>  		 * Disable the DSI clock output, see
>  		 * rcar_du_crtc_atomic_enable().
> diff --git a/drivers/gpu/drm/renesas/rcar-du/rcar_mipi_dsi.c b/drivers/gpu/drm/renesas/rcar-du/rcar_mipi_dsi.c
> index aaafee1c060b..f429f03a380c 100644
> --- a/drivers/gpu/drm/renesas/rcar-du/rcar_mipi_dsi.c
> +++ b/drivers/gpu/drm/renesas/rcar-du/rcar_mipi_dsi.c
> @@ -957,6 +957,7 @@ static int rcar_mipi_dsi_host_attach(struct mipi_dsi_host *host,
>  
>  	/* Initialize the DRM bridge. */
>  	dsi->bridge.of_node = dsi->dev->of_node;
> +	dsi->bridge.type = DRM_MODE_CONNECTOR_DSI;
>  	drm_bridge_add(&dsi->bridge);
>  
>  	return 0;

-- 
Regards,

Laurent Pinchart