linux-kernel - Re: [PATCH v9 11/19] media: ti: j721e-csi2rx: add support for processing virtual channels

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Message-ID: <bd2ee047-efd8-477b-bcdc-27047a1023cc@ideasonboard.com>
Date: Wed, 14 Jan 2026 17:31:56 +0200
From: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To: Rishikesh Donadkar <r-donadkar@...com>
Cc: y-abhilashchandra@...com, devarsht@...com, s-jain1@...com,
 vigneshr@...com, mchehab@...nel.org, robh@...nel.org, krzk+dt@...nel.org,
 p.zabel@...gutronix.de, conor+dt@...nel.org, sakari.ailus@...ux.intel.com,
 hverkuil-cisco@...all.nl, jai.luthra@...asonboard.com,
 changhuang.liang@...rfivetech.com, jack.zhu@...rfivetech.com,
 sjoerd@...labora.com, dan.carpenter@...aro.org, hverkuil+cisco@...nel.org,
 linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
 devicetree@...r.kernel.org, jai.luthra@...ux.dev,
 laurent.pinchart@...asonboard.com, mripard@...nel.org
Subject: Re: [PATCH v9 11/19] media: ti: j721e-csi2rx: add support for
 processing virtual channels

Hi,

On 30/12/2025 10:32, Rishikesh Donadkar wrote:
> From: Jai Luthra <j-luthra@...com>
> 
> Use get_frame_desc() to get the frame desc from the connected source,
> and use the provided virtual channel instead of VC 0.
> 
> get_frame_desc() works for single stream case, but as we don't

Is that supposed to say "get_frame_desc works for multi-stream use case"?

> 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.
> 
> Reviewed-by: Yemike Abhilash Chandra <y-abhilashchandra@...com>
> Co-developed-by: Pratyush Yadav <p.yadav@...com>
> Signed-off-by: Pratyush Yadav <p.yadav@...com>
> Signed-off-by: Jai Luthra <j-luthra@...com>
> Signed-off-by: Rishikesh Donadkar <r-donadkar@...com>
> ---
>  .../platform/ti/j721e-csi2rx/j721e-csi2rx.c   | 45 ++++++++++++++++++-
>  1 file changed, 44 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c b/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c
> index f54ad67ff3f9d..6f9f34aa26f1b 100644
> --- a/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c
> +++ b/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c
> @@ -32,6 +32,7 @@
>  #define SHIM_DMACNTX_YUV422		GENMASK(27, 26)
>  #define SHIM_DMACNTX_DUAL_PCK_CFG	BIT(24)
>  #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
> @@ -110,6 +111,9 @@ struct ti_csi2rx_ctx {
>  	struct media_pad		pad;
>  	u32				sequence;
>  	u32				idx;
> +	u32				vc;
> +	u32				dt;
> +	u32				stream;
>  };
>  
>  struct ti_csi2rx_dev {
> @@ -570,7 +574,7 @@ static void ti_csi2rx_setup_shim(struct ti_csi2rx_ctx *ctx)
>  	ti_csi2rx_request_max_ppc(csi);
>  
>  	reg = SHIM_DMACNTX_EN;
> -	reg |= FIELD_PREP(SHIM_DMACNTX_FMT, fmt->csi_dt);
> +	reg |= FIELD_PREP(SHIM_DMACNTX_FMT, ctx->dt);
>  
>  	/*
>  	 * The hardware assumes incoming YUV422 8-bit data on MIPI CSI2 bus
> @@ -610,6 +614,7 @@ 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));
>  
> @@ -884,12 +889,41 @@ static void ti_csi2rx_buffer_queue(struct vb2_buffer *vb)
>  	}
>  }
>  
> +static int ti_csi2rx_get_vc_and_dt(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;
> +
> +	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) {
> +			ctx->vc = fd.entry[i].bus.csi2.vc;
> +			ctx->dt = fd.entry[i].bus.csi2.dt;
> +		}
> +	}

I think you can "break" when you find the stream. But this should also
catch the case when there's no matching stream, and give an error in
that case.

 Tomi

> +
> +	return 0;
> +}
> +
>  static int ti_csi2rx_start_streaming(struct vb2_queue *vq, unsigned int count)
>  {
>  	struct ti_csi2rx_ctx *ctx = vb2_get_drv_priv(vq);
>  	struct ti_csi2rx_dev *csi = ctx->csi;
>  	struct ti_csi2rx_dma *dma = &ctx->dma;
>  	struct ti_csi2rx_buffer *buf;
> +	const struct ti_csi2rx_fmt *fmt;
>  	unsigned long flags;
>  	int ret = 0;
>  
> @@ -904,6 +938,15 @@ static int ti_csi2rx_start_streaming(struct vb2_queue *vq, unsigned int count)
>  	if (ret)
>  		goto err;
>  
> +	ret = ti_csi2rx_get_vc_and_dt(ctx);
> +	if (ret == -ENOIOCTLCMD) {
> +		ctx->vc = 0;
> +		fmt = find_format_by_fourcc(ctx->v_fmt.fmt.pix.pixelformat);
> +		ctx->dt = fmt->csi_dt;
> +	} else if (ret < 0) {
> +		goto err;
> +	}
> +
>  	ti_csi2rx_setup_shim(ctx);
>  
>  	ctx->sequence = 0;