Re: [PATCH 1/9] media: rzg2l-cru: Add device_link from CRU to CSI-2

[Jacopo Mondi]

Hi Tommaso
 one more thing

On Tue, Jun 16, 2026 at 07:05:31PM +0200, Tommaso Merciai wrote:
> The CRU device depends on CSI-2 to operate. Without an explicit
> device_link the PM core has no knowledge of this dependency and may
> suspend CSI-2 while CRU is still active, or resume CRU before CSI-2
> is ready.
>
> Add a DL_FLAG_STATELESS device_link from the CRU to CSI-2 when the
> CSI-2 subdev binds. This instructs the PM core to suspend CRU before
> CSI-2 and to resume CSI-2 before CRU. The link is deleted on unbind.
>
> Signed-off-by: Tommaso Merciai <tommaso.merciai.xr@xxxxxxxxxxxxxx>
> ---
>  drivers/media/platform/renesas/rzg2l-cru/rzg2l-core.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-core.c b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-core.c
> index 3c5fbd857371..1b12d91eaec9 100644
> --- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-core.c
> +++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-core.c
> @@ -101,6 +101,7 @@ static void rzg2l_cru_group_notify_unbind(struct v4l2_async_notifier *notifier,
>  	mutex_lock(&cru->mdev_lock);

What is the mutex protecting here ?

(yes, unrelated to this patch, I know, just wondering if you should
take the occasion to remove the guards from bind/unbind)

>
>  	if (cru->csi.asd == asd) {
> +		device_link_remove(cru->dev, subdev->dev);
>  		cru->csi.subdev = NULL;
>  		dev_dbg(cru->dev, "Unbind CSI-2 %s\n", subdev->name);
>  	}
> @@ -118,6 +119,12 @@ static int rzg2l_cru_group_notify_bound(struct v4l2_async_notifier *notifier,
>
>  	if (cru->csi.asd == asd) {
>  		cru->csi.subdev = subdev;
> +		if (!device_link_add(cru->dev, subdev->dev, DL_FLAG_STATELESS)) {
> +			dev_err(cru->dev, "Failed to create device link to CSI-2 %s\n",
> +				subdev->name);
> +			mutex_unlock(&cru->mdev_lock);
> +			return -EINVAL;
> +		}
>  		dev_dbg(cru->dev, "Bound CSI-2 %s\n", subdev->name);
>  	}
>
> --
> 2.54.0
>