Re: [PATCH v3 08/13] media: ti: j721e-csi2rx: add support for processing virtual channels

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Rishikesh,

Thank you for the patch.

On Thu, Apr 17, 2025 at 12:25:49PM +0530, Rishikesh Donadkar wrote:
> From: Jai Luthra <j-luthra@ti.com>
> 
> Use get_frame_desc() to get the frame desc from the connected source,
> and use the provided virtual channel instead of hardcoded one.
> 
> get_frame_desc() works per stream, but as we don't support multiple
> streams yet, we will just always use stream 0. If the source doesn't
> support get_frame_desc(), fall back to the previous method of always
> capturing virtual channel 0.
> 
> Co-developed-by: Pratyush Yadav <p.yadav@ti.com>
> Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
> Signed-off-by: Jai Luthra <j-luthra@ti.com>
> Signed-off-by: Rishikesh Donadkar <r-donadkar@ti.com>
> ---
>  .../platform/ti/j721e-csi2rx/j721e-csi2rx.c   | 39 +++++++++++++++++++
>  1 file changed, 39 insertions(+)
> 
> diff --git a/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c b/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c
> index e85d04d7c2ff9..3e2a0517a9096 100644
> --- a/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c
> +++ b/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c
> @@ -29,6 +29,7 @@
>  #define SHIM_DMACNTX_EN			BIT(31)
>  #define SHIM_DMACNTX_YUV422		GENMASK(27, 26)
>  #define SHIM_DMACNTX_SIZE		GENMASK(21, 20)
> +#define SHIM_DMACNTX_VC			GENMASK(9, 6)
>  #define SHIM_DMACNTX_FMT		GENMASK(5, 0)
>  #define SHIM_DMACNTX_YUV422_MODE_11	3
>  #define SHIM_DMACNTX_SIZE_8		0
> @@ -105,6 +106,8 @@ struct ti_csi2rx_ctx {
>  	struct media_pad		pad;
>  	u32				sequence;
>  	u32				idx;
> +	u32				vc;
> +	u32				stream;
>  };
>  
>  struct ti_csi2rx_dev {
> @@ -573,6 +576,7 @@ static void ti_csi2rx_setup_shim(struct ti_csi2rx_ctx *ctx)
>  	}
>  
>  	reg |= FIELD_PREP(SHIM_DMACNTX_SIZE, fmt->size);
> +	reg |= FIELD_PREP(SHIM_DMACNTX_VC, ctx->vc);
>  
>  	writel(reg, csi->shim + SHIM_DMACNTX(ctx->idx));
>  
> @@ -846,6 +850,33 @@ static void ti_csi2rx_buffer_queue(struct vb2_buffer *vb)
>  	}
>  }
>  
> +static int ti_csi2rx_get_vc(struct ti_csi2rx_ctx *ctx)
> +{
> +	struct ti_csi2rx_dev *csi = ctx->csi;
> +	struct v4l2_mbus_frame_desc fd;
> +	struct media_pad *pad;
> +	int ret, i;

i can never be negative, you can make it an unsigned int.

> +
> +	pad = media_entity_remote_pad_unique(&csi->subdev.entity, MEDIA_PAD_FL_SOURCE);
> +	if (!pad)
> +		return -ENODEV;
> +
> +	ret = v4l2_subdev_call(csi->source, pad, get_frame_desc, pad->index,
> +			       &fd);
> +	if (ret)
> +		return ret;
> +
> +	if (fd.type != V4L2_MBUS_FRAME_DESC_TYPE_CSI2)
> +		return -EINVAL;
> +
> +	for (i = 0; i < fd.num_entries; i++) {
> +		if (ctx->stream == fd.entry[i].stream)
> +			return fd.entry[i].bus.csi2.vc;
> +	}
> +
> +	return -ENODEV;
> +}
> +
>  static int ti_csi2rx_start_streaming(struct vb2_queue *vq, unsigned int count)
>  {
>  	struct ti_csi2rx_ctx *ctx = vb2_get_drv_priv(vq);
> @@ -866,6 +897,14 @@ static int ti_csi2rx_start_streaming(struct vb2_queue *vq, unsigned int count)
>  	if (ret)
>  		goto err;
>  
> +	ret = ti_csi2rx_get_vc(ctx);
> +	if (ret == -ENOIOCTLCMD)
> +		ctx->vc = 0;
> +	else if (ret < 0)
> +		goto err;
> +	else
> +		ctx->vc = ret;
> +

When you'll add support for multiple streams in patch 11/13, you will
end up calling .get_frame_desc() once per stream. All calls will return
the same information, so it's a bit wasteful. Would it be possible to
call this function once only at start time, and cache and use the
results for all video devices ?

>  	ti_csi2rx_setup_shim(ctx);
>  
>  	ctx->sequence = 0;

-- 
Regards,

Laurent Pinchart