Re: [PATCH v5 1/5] media: rzg2l-cru: Align bytesperline to hardware DMA stride requirement

[Jacopo Mondi <jacopo.mondi@ideasonboard.com>]

Hi Tommaso

On Wed, Jul 29, 2026 at 12:55:46PM +0200, Tommaso Merciai wrote:
> The RZ/G3E CRU programs the line stride via the AMnIS register, whose
> IS field encodes the value in units of 128 bytes. If bytesperline is
> not a multiple of 128, the division truncates and the hardware uses a
> wrong stride, causing horizontal banding.
>
> Commit ace92ccef0c9 ("media: platform: rzg2l-cru: Use v4l2_fill_pixfmt()")
> replaced the open-coded aligned calculation with v4l2_fill_pixfmt(),
> which sets no alignment, reintroducing the issue.
>
> Round bytesperline up to RZG2L_CRU_STRIDE_ALIGN and recompute
> sizeimage when info->has_stride is set. RZ/G2L has no AMnIS register
> and keeps the values from v4l2_fill_pixfmt() unchanged.
>
> Fixes: ace92ccef0c9 ("media: platform: rzg2l-cru: Use v4l2_fill_pixfmt()")
> Cc: stable@vger.kernel.org
> Signed-off-by: Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>
> ---
> v4->v5:
>  - New patch.
>
>  drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> index 5185a547461d..91eda5034248 100644
> --- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> +++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> @@ -851,6 +851,11 @@ static void rzg2l_cru_format_align(struct rzg2l_cru_dev *cru,
>
>  	v4l2_fill_pixfmt(pix, pix->pixelformat, pix->width, pix->height);
>
> +	if (info->has_stride) {
> +		pix->bytesperline = ALIGN(pix->bytesperline, RZG2L_CRU_STRIDE_ALIGN);
> +		pix->sizeimage = pix->bytesperline * pix->height;
> +	}
> +

Ack! I think this does what is expected for the single planar formats
the CRU supports!

I think after this cycle you could send a patch to replace the above
back-portable change with the usage of v4l2_fill_pixfmt_aligned().

When you do so, could you consider, replacing "has_stride" with a per
struct rzg2l_cru_info .stride field ?

I think it would look nicer as you could here unconditionally align
(assuming the new .stride will be set to 1 for G2L which currently has
.has_stride = 0).

Also, RZG2L_CRU_STRIDE_ALIGN is a bit of a mis-nomer, as only G3E and
V2H has a AMnIS register and alignments constraints as far as I see.

The only other user of 'has_stride' I see is:

 rzg2l_cru_initialize_axi()

	if (info->has_stride) {
		u32 stride = cru->format.bytesperline;
		u32 amnis;

		stride /= RZG2L_CRU_STRIDE_ALIGN;
		amnis = rzg2l_cru_read(cru, AMnIS) & ~AMnIS_IS_MASK;
		rzg2l_cru_write(cru, AMnIS, amnis | AMnIS_IS(stride));
	}

the G2L has no register AMnIS, so we can't write it unconditionally
but rather replace the check with:

        if (info->stride > 1)

As a bonus, if any other variant will get a different stride, it will
be automatically supported.

What do you think ?

In the meantime for this patch
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>

Thanks
  j


>  	dev_dbg(cru->dev, "Format %ux%u bpl: %u size: %u\n",
>  		pix->width, pix->height, pix->bytesperline, pix->sizeimage);
>  }
> --
> 2.54.0
>
>