Re: [PATCH v8 11/18] media: ti: j721e-csi2rx: add support for processing virtual channels
From: Rishikesh Donadkar
Date: Mon Dec 01 2025 - 04:26:03 EST
On 20/11/25 18:02, Tomi Valkeinen wrote:
Hi,
Hi Tomi,
On 12/11/2025 13:54, Rishikesh Donadkar wrote:
From: Jai Luthra <j-luthra@xxxxxx>
Use get_frame_desc() to get the frame desc from the connected source,
and use the provided virtual channel instead of hardcoded one.
So this baffled me a bit: the code seems to get the VC from the frame
desc, but not the DT. But it looks like the DT values are hardcoded in
the driver's formats table, and those are used for DT filtering.
Previous to this, we were using default VC 0(hard coded), In this patch
we change it to use the one returned by the get_frame_desc(). I will
edit the commit message to mention this properly.
Yes, to filter on the basis of DT we use the DT form the the driver's
format table.
We need to do something like that for legacy cases where the source does
not support get_frame_desc, but if there is a frame desc, we should use
the DT and VC from the frame desc.
Sure, I will change this in the next revision.
get_frame_desc() returns the same information when called on each stream
start, so instead get the VCs for all the routed stream at first
stream start and cache this information in the driver.
I get the point but... There isn't anything like this in the patch?
Thanks for pointing out, I moved the code to do this in the patch 13/18
between v7->v8. I will remove this form the commit message.
get_frame_desc() works per stream, but as we don't support multiple
"get_frame_desc() works per stream", what does it mean? It returns all
the streams for a pad.
This means that get_frame_desc() works for single stream use case as
well, I will change the commit message.
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.
Right, if there's no frame desc (and we need to support legacy drivers),
the driver should default to VC=0, DT from the formats table. But as
mentioned above, VC and DT should normally come from the frame desc. It
I will change this in the next revision.
Rishikesh
would be good to have a separate "legacy" function/branch/something, so
that we clearly distinguish the legacy and frame-desc cases.
Tomi
Reviewed-by: Yemike Abhilash Chandra <y-abhilashchandra@xxxxxx>
Co-developed-by: Pratyush Yadav <p.yadav@xxxxxx>
Signed-off-by: Pratyush Yadav <p.yadav@xxxxxx>
Signed-off-by: Jai Luthra <j-luthra@xxxxxx>
Signed-off-by: Rishikesh Donadkar <r-donadkar@xxxxxx>
---
.../platform/ti/j721e-csi2rx/j721e-csi2rx.c | 38 +++++++++++++++++++
1 file changed, 38 insertions(+)
diff --git a/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c b/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c
index 5c4524bf42e6e..126a62fa2c4c4 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 +111,8 @@ struct ti_csi2rx_ctx {
struct media_pad pad;
u32 sequence;
u32 idx;
+ u32 vc;
+ u32 stream;
};
struct ti_csi2rx_dev {
@@ -610,6 +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));
@@ -884,6 +888,32 @@ 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;
+
+ 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);
@@ -904,6 +934,14 @@ 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;
+
ti_csi2rx_setup_shim(ctx);
ctx->sequence = 0;