Re: [PATCH] drm: rz-du: Ensure correct suspend/resume ordering with VSP

[Laurent Pinchart]

On Tue, Mar 24, 2026 at 07:05:05PM +0100, Tommaso Merciai wrote:
> The VSP serves as an interface to memory and a compositor to the DU. It
> therefore needs to be suspended after and resumed before the DU, to be
> properly stopped and restarted in a controlled fashion driven by the DU
> driver. This currently works by chance. Avoid relying on luck by
> enforcing the correct suspend/resume ordering with device links.
> 
> Based on similar work done by Laurent Pinchart for R-Car DU.

If the R-Car DU patch gets merged before this one, you could mention the
commit ID here.

> 
> Signed-off-by: Tommaso Merciai <tommaso.merciai.xr@xxxxxxxxxxxxxx>

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

> ---
>  drivers/gpu/drm/renesas/rz-du/rzg2l_du_vsp.c | 16 ++++++++++++++++
>  drivers/gpu/drm/renesas/rz-du/rzg2l_du_vsp.h |  2 ++
>  2 files changed, 18 insertions(+)
> 
> diff --git a/drivers/gpu/drm/renesas/rz-du/rzg2l_du_vsp.c b/drivers/gpu/drm/renesas/rz-du/rzg2l_du_vsp.c
> index bd486377f037..eb626c3cc421 100644
> --- a/drivers/gpu/drm/renesas/rz-du/rzg2l_du_vsp.c
> +++ b/drivers/gpu/drm/renesas/rz-du/rzg2l_du_vsp.c
> @@ -20,6 +20,7 @@
>  #include <drm/drm_vblank.h>
>  
>  #include <linux/bitops.h>
> +#include <linux/device.h>
>  #include <linux/dma-mapping.h>
>  #include <linux/of_platform.h>
>  #include <linux/platform_device.h>
> @@ -293,6 +294,9 @@ static void rzg2l_du_vsp_cleanup(struct drm_device *dev, void *res)
>  {
>  	struct rzg2l_du_vsp *vsp = res;
>  
> +	if (vsp->link)
> +		device_link_del(vsp->link);
> +
>  	put_device(vsp->vsp);
>  }
>  
> @@ -317,6 +321,18 @@ int rzg2l_du_vsp_init(struct rzg2l_du_vsp *vsp, struct device_node *np,
>  	if (ret < 0)
>  		return ret;
>  
> +	/*
> +	 * Enforce suspend/resume ordering between the DU (consumer) and the
> +	 * VSP (supplier). The DU will be suspended before and resume after the
> +	 * VSP.
> +	 */
> +	vsp->link = device_link_add(rcdu->dev, vsp->vsp, DL_FLAG_STATELESS);
> +	if (!vsp->link) {
> +		dev_err(rcdu->dev, "Failed to create device link to VSP %s\n",
> +			dev_name(vsp->vsp));
> +		return -EINVAL;
> +	}
> +
>  	ret = vsp1_du_init(vsp->vsp);
>  	if (ret < 0)
>  		return ret;
> diff --git a/drivers/gpu/drm/renesas/rz-du/rzg2l_du_vsp.h b/drivers/gpu/drm/renesas/rz-du/rzg2l_du_vsp.h
> index 322eb80dcbaf..a22aaf0843ed 100644
> --- a/drivers/gpu/drm/renesas/rz-du/rzg2l_du_vsp.h
> +++ b/drivers/gpu/drm/renesas/rz-du/rzg2l_du_vsp.h
> @@ -15,6 +15,7 @@
>  #include <linux/scatterlist.h>
>  
>  struct device;
> +struct device_link;
>  struct drm_framebuffer;
>  struct rzg2l_du_device;
>  struct rzg2l_du_format_info;
> @@ -29,6 +30,7 @@ struct rzg2l_du_vsp_plane {
>  struct rzg2l_du_vsp {
>  	unsigned int index;
>  	struct device *vsp;
> +	struct device_link *link;
>  	struct rzg2l_du_device *dev;
>  };
>  

-- 
Regards,

Laurent Pinchart