Re: Re: [PATCH v2 09/13] media: ti: j721e-csi2rx: add support for processing virtual channels

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Hi Jacopo,

On Jul 12, 2024 at 17:01:04 +0200, Jacopo Mondi wrote:
> Hi Jai
> 
> On Thu, Jun 27, 2024 at 06:40:04PM GMT, Jai Luthra wrote:
> > 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@xxxxxx>
> > Signed-off-by: Pratyush Yadav <p.yadav@xxxxxx>
> > Signed-off-by: Jai Luthra <j-luthra@xxxxxx>
> > ---
> >  .../media/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 b4b4bb69c88a..c0916ca1a6f8 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 {
> > @@ -571,6 +574,7 @@ 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));
> >
> > @@ -844,6 +848,33 @@ 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;
> > +
> > +	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;
> 
> Would it be better to fail at bound() time if the remote subdev
> doesn't support get_frame_desc ? you can use
> 
>         if (!v4l2_subdev_has_op(subdev, pad, get_frame_desc)) {
> 
> > +
> > +	if (fd.type != V4L2_MBUS_FRAME_DESC_TYPE_CSI2)
> > +		return -EINVAL;
> > +
> > +	for (i = 0; i < fd.num_entries; i++) {
> 
>         for (unsigned int i
> 
> should num_entries be validated ?
> 
> > +		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);
> > @@ -864,6 +895,14 @@ 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;
> 
> Ah, so you fallback to 0 in case the subdev doesn't support
> get_frame_desc. I'm not sure what would be better here maybe wait for
> other's opinions as well.
> 
> Personally I would fail earlier to make sure subdev drivers are forced
> to impement get_frame_desc
> 

Before we break support for all non-streams-aware subdevs, I think maybe 
we need a default v4l2_subdev_get_frame_desc() helper that returns a 
single entry with stream = 0 and csi2.vc = 0, as that is usually what 
most sensors do.

> > +	else if (ret < 0)
> > +		goto err;
> > +	else
> > +		ctx->vc = ret;
> > +
> >  	ti_csi2rx_setup_shim(ctx);
> >
> >  	ctx->sequence = 0;
> >
> > --
> > 2.43.0
> >
> >

-- 
Thanks,
Jai

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