linux-kernel - Re: [PATCH 2/3] media: platform: rzg2l-cru: rzg2l-video: Retrieve virtual channel information

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Message-ID: <20240906231038.GC12915@pendragon.ideasonboard.com>
Date: Sat, 7 Sep 2024 02:10:38 +0300
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Prabhakar <prabhakar.csengg@...il.com>
Cc: Sakari Ailus <sakari.ailus@...ux.intel.com>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	Hans Verkuil <hverkuil-cisco@...all.nl>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-renesas-soc@...r.kernel.org,
	Biju Das <biju.das.jz@...renesas.com>,
	Fabrizio Castro <fabrizio.castro.jz@...esas.com>,
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH 2/3] media: platform: rzg2l-cru: rzg2l-video: Retrieve
 virtual channel information

Hi Prabhakar,

Thank you for the patch.

On Fri, Sep 06, 2024 at 06:39:46PM +0100, Prabhakar wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> 
> The RZ/G2L CRU needs to configure the ICnMC.VCSEL bits to specify which
> virtual channel should be processed from the four available VCs. To
> retrieve this information from the connected subdevice, the
> .get_frame_desc() function is called.
> 
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> ---
>  .../platform/renesas/rzg2l-cru/rzg2l-video.c  | 29 +++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> index bbf4674f888d..6101a070e785 100644
> --- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> +++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> @@ -433,12 +433,41 @@ void rzg2l_cru_stop_image_processing(struct rzg2l_cru_dev *cru)
>  	spin_unlock_irqrestore(&cru->qlock, flags);
>  }
>  
> +static int rzg2l_cru_get_virtual_channel(struct rzg2l_cru_dev *cru)
> +{
> +	struct v4l2_mbus_frame_desc fd = { };
> +	struct media_pad *pad;
> +	int ret;
> +
> +	pad = media_pad_remote_pad_unique(&cru->ip.pads[1]);

It would be nice to use RZG2L_CRU_IP_SOURCE here instead of hardcoding
the pad number. That would require moving rzg2l_csi2_pads to the shared
header. You can do that on top.

An now that I've said that, is it really the source pad you need here ?

> +	if (IS_ERR(pad))
> +		return PTR_ERR(pad);

Can this happen, or would the pipeline fail to validate ? I think you
can set the MUST_CONNECT flag on the sink pad, then you'll have a
guarantee something will be connected.

> +
> +	ret = v4l2_subdev_call(cru->ip.remote, pad, get_frame_desc,
> +			       pad->index, &fd);
> +	if (ret < 0 && ret != -ENOIOCTLCMD)

Printing an error message would help debugging.

> +		return ret;
> +	/* If remote subdev does not implement .get_frame_desc default to VC0. */
> +	if (ret == -ENOIOCTLCMD)
> +		return 0;
> +
> +	if (fd.type != V4L2_MBUS_FRAME_DESC_TYPE_CSI2)

An error message would help here too I think.

> +		return -EINVAL;
> +
> +	return fd.num_entries ? fd.entry[0].bus.csi2.vc : 0;

I think you should return an error if fd.num_entries is 0, that
shouldn't happen.

> +}
> +
>  int rzg2l_cru_start_image_processing(struct rzg2l_cru_dev *cru)
>  {
>  	struct v4l2_mbus_framefmt *fmt = rzg2l_cru_ip_get_src_fmt(cru);
>  	unsigned long flags;
>  	int ret;
>  
> +	ret = rzg2l_cru_get_virtual_channel(cru);
> +	if (ret < 0)
> +		return ret;
> +	cru->csi.channel = ret;

How about passing the value to the function that needs it, instead of
storing it in cru->csi.channel ? You can do that on top and drop the
csi.channel field.

Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

> +
>  	spin_lock_irqsave(&cru->qlock, flags);
>  
>  	/* Select a video input */

-- 
Regards,

Laurent Pinchart