Re: [PATCH v5 4/7] drm/rcar-du: dsi: Support DSC in the pipeline

[Laurent Pinchart]

Hi Tomi,

Thank you for the patch.

On Mon, Jun 15, 2026 at 04:11:57PM +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, make sure we store the DSI bridge to the
> rcdu->dsi[] array, instead of the first bridge in the DSI pipeline
> (which can be DCS), by checking the bridge's bridge->type.
> 
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas@xxxxxxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/renesas/rcar-du/rcar_du_encoder.c | 18 ++++++++++++++++--
>  drivers/gpu/drm/renesas/rcar-du/rcar_mipi_dsi.c   |  1 +
>  2 files changed, 17 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/renesas/rcar-du/rcar_du_encoder.c b/drivers/gpu/drm/renesas/rcar-du/rcar_du_encoder.c
> index db2088529b48..ac85838ab3b8 100644
> --- a/drivers/gpu/drm/renesas/rcar-du/rcar_du_encoder.c
> +++ b/drivers/gpu/drm/renesas/rcar-du/rcar_du_encoder.c
> @@ -89,9 +89,23 @@ int rcar_du_encoder_init(struct rcar_du_device *rcdu,
>  				drm_bridge_get(bridge);
>  
>  		if (output == RCAR_DU_OUTPUT_DSI0 ||
> -		    output == RCAR_DU_OUTPUT_DSI1)
> +		    output == RCAR_DU_OUTPUT_DSI1) {
> +			struct drm_bridge *dsi_bridge;
> +
> +			/*
> +			 * 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.
> +			 */
> +
> +			dsi_bridge = bridge->type == DRM_MODE_CONNECTOR_DSI ?
> +						     bridge :
> +						     bridge->next_bridge;

The indentation looks weird.

			dsi_bridge = bridge->type == DRM_MODE_CONNECTOR_DSI
				   ? bridge : bridge->next_bridge;

Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@xxxxxxxxxxxxxxxx>

> +
>  			rcdu->dsi[output - RCAR_DU_OUTPUT_DSI0] =
> -				drm_bridge_get(bridge);
> +				drm_bridge_get(dsi_bridge);
> +		}
>  	}
>  
>  	/*
> 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