Re: [PATCH 2/9] media: rzg2l-cru: csi2: Add device_link from CSI-2 to sensor

[Jacopo Mondi <jacopo.mondi@ideasonboard.com>]

Hi Tommaso

On Tue, Jun 16, 2026 at 07:05:32PM +0200, Tommaso Merciai wrote:
> The CSI-2 receiver depends on its remote sensor being powered and
> configured before it can receive data. Without an explicit device_link
> the PM core has no knowledge of this dependency and may suspend the
> sensor while CSI-2 is still active, or resume CSI-2 before the sensor
> is ready.
>
> Add a DL_FLAG_STATELESS device_link from the CSI-2 device to the sensor
> device when the sensor subdev binds. This instructs the PM core to
> suspend CSI-2 before the sensor and to resume the sensor before CSI-2.
> The link is deleted on unbind.
>
> Move csi2->remote_source assignment to the end of the function.
>
> Signed-off-by: Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>
> ---
>  .../platform/renesas/rzg2l-cru/rzg2l-csi2.c   | 24 +++++++++++++++----
>  1 file changed, 19 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-csi2.c b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-csi2.c
> index 6dc4b53607b4..3a4bc4ef72fc 100644
> --- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-csi2.c
> +++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-csi2.c
> @@ -773,15 +773,28 @@ static int rzg2l_csi2_notify_bound(struct v4l2_async_notifier *notifier,
>  				   struct v4l2_async_connection *asd)
>  {
>  	struct rzg2l_csi2 *csi2 = notifier_to_csi2(notifier);
> +	int ret;
>
> -	csi2->remote_source = subdev;
> +	if (!device_link_add(csi2->dev, subdev->dev, DL_FLAG_STATELESS)) {

As cru-csi2 supports runtime suspend/resume, should you also add
DL_FLAG_PM_RUNTIME ?

> +		dev_err(csi2->dev, "Failed to create device link to sensor %s\n",
> +			subdev->name);
> +		return -EINVAL;
> +	}
>
>  	dev_dbg(csi2->dev, "Bound subdev: %s pad\n", subdev->name);
>
> -	return media_create_pad_link(&subdev->entity, RZG2L_CSI2_SINK,
> -				     &csi2->subdev.entity, 0,
> -				     MEDIA_LNK_FL_ENABLED |
> -				     MEDIA_LNK_FL_IMMUTABLE);
> +	ret = media_create_pad_link(&subdev->entity, RZG2L_CSI2_SINK,
> +				    &csi2->subdev.entity, 0,
> +				    MEDIA_LNK_FL_ENABLED |
> +				    MEDIA_LNK_FL_IMMUTABLE);
> +	if (ret) {
> +		device_link_remove(csi2->dev, subdev->dev);
> +		return ret;
> +	}
> +
> +	csi2->remote_source = subdev;
> +
> +	return 0;
>  }
>
>  static void rzg2l_csi2_notify_unbind(struct v4l2_async_notifier *notifier,
> @@ -790,6 +803,7 @@ static void rzg2l_csi2_notify_unbind(struct v4l2_async_notifier *notifier,
>  {
>  	struct rzg2l_csi2 *csi2 = notifier_to_csi2(notifier);
>
> +	device_link_remove(csi2->dev, subdev->dev);
>  	csi2->remote_source = NULL;
>
>  	dev_dbg(csi2->dev, "Unbind subdev %s\n", subdev->name);
> --
> 2.54.0
>