linux-kernel - Re: [PATCH v10 10/18] media: ti: j721e-csi2rx: add support for processing virtual channels

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Message-ID: <352c16f3-7aa7-4d4c-b3ba-4e84fae3b384@ti.com>
Date: Fri, 30 Jan 2026 09:30:28 +0530
From: Rishikesh Donadkar <r-donadkar@...com>
To: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>, <jai.luthra@...ux.dev>,
	<laurent.pinchart@...asonboard.com>, <mripard@...nel.org>
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>
Subject: Re: [PATCH v10 10/18] media: ti: j721e-csi2rx: add support for
 processing virtual channels


On 23/01/26 14:20, Tomi Valkeinen wrote:
> Hi,

Hi Tomi,

Thank you for the review !

>
> On 21/01/2026 15:54, 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.
> Not only VC, but also DT is handled here.


Thanks for pointing out, will update the commit message !

Rishikesh

>
>> 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.
>>
>> 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   | 50 ++++++++++++++++++-
>>   1 file changed, 49 insertions(+), 1 deletion(-)
> Reviewed-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
>
>   Tomi
>
>> diff --git a/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c b/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c
>> index aa038d1badc07..81c86e2cc4a50 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 {
>> @@ -569,7 +573,7 @@ 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
>> @@ -609,6 +613,7 @@ 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));
>>   
>> @@ -883,12 +888,46 @@ 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;
>> +			break;
>> +		}
>> +
>> +		/* Return error if no matching stream found */
>> +		if (i == fd.num_entries)
>> +			return -EINVAL;
>> +	}
>> +
>> +	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;
>>   
>> @@ -903,6 +942,15 @@ 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;