Re: [PATCH v2 16/23] staging: media: tegra-video: tegra20: simplify format align calculations

Svyatoslav Ryhel
2025-09-22T06:31:00Z

пн, 22 вер. 2025 р. о 09:23 Mikko Perttunen <mperttunen@nvidia.com> пише:
>
> On Monday, September 22, 2025 2:13 PM Svyatoslav Ryhel wrote:
> > пн, 22 вер. 2025 р. о 07:44 Mikko Perttunen <mperttunen@nvidia.com> пише:
> > >
> > > On Saturday, September 6, 2025 10:53 PM Svyatoslav Ryhel wrote:
> > > > Simplify format align calculations by slightly modifying supported formats
> > > > structure.
> > > >
> > > > Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>
> > > > ---
> > > > drivers/staging/media/tegra-video/tegra20.c | 41 ++++++++-------------
> > > > 1 file changed, 16 insertions(+), 25 deletions(-)
> > > >
> > > > diff --git a/drivers/staging/media/tegra-video/tegra20.c b/drivers/staging/media/tegra-video/tegra20.c
> > > > index 6e0b3b728623..781c4e8ec856 100644
> > > > --- a/drivers/staging/media/tegra-video/tegra20.c
> > > > +++ b/drivers/staging/media/tegra-video/tegra20.c
> > > > @@ -280,20 +280,8 @@ static void tegra20_fmt_align(struct v4l2_pix_format *pix, unsigned int bpp)
> > > > pix->width = clamp(pix->width, TEGRA20_MIN_WIDTH, TEGRA20_MAX_WIDTH);
> > > > pix->height = clamp(pix->height, TEGRA20_MIN_HEIGHT, TEGRA20_MAX_HEIGHT);
> > > >
> > > > - switch (pix->pixelformat) {
> > > > - case V4L2_PIX_FMT_UYVY:
> > > > - case V4L2_PIX_FMT_VYUY:
> > > > - case V4L2_PIX_FMT_YUYV:
> > > > - case V4L2_PIX_FMT_YVYU:
> > > > - pix->bytesperline = roundup(pix->width, 2) * 2;
> > > > - pix->sizeimage = roundup(pix->width, 2) * 2 * pix->height;
> > > > - break;
> > > > - case V4L2_PIX_FMT_YUV420:
> > > > - case V4L2_PIX_FMT_YVU420:
> > > > - pix->bytesperline = roundup(pix->width, 8);
> > > > - pix->sizeimage = roundup(pix->width, 8) * pix->height * 3 / 2;
> > > > - break;
> > > > - }
> > > > + pix->bytesperline = DIV_ROUND_UP(pix->width * bpp, 8);
> > >
> > > Assuming the bpp is coming from the format table below, this changes the value of bytesperline for planar formats. With this it'll be (width * 12) / 8 i.e. width * 3/2, which doesn't sound right.
> > >
> >
> > Downstream uses soc_mbus_bytes_per_line for this calculation which was
> > deprecated some time ago, here is a fragment
> >
> > s32 soc_mbus_bytes_per_line(u32 width, const struct soc_mbus_pixelfmt *mf)
> > {
> > if (mf->fourcc == V4L2_PIX_FMT_JPEG)
> > return 0;
> >
> > if (mf->layout != SOC_MBUS_LAYOUT_PACKED)
> > return width * mf->bits_per_sample / 8;
> >
> > switch (mf->packing) {
> > case SOC_MBUS_PACKING_NONE:
> > return width * mf->bits_per_sample / 8;
> > case SOC_MBUS_PACKING_2X8_PADHI:
> > case SOC_MBUS_PACKING_2X8_PADLO:
> > case SOC_MBUS_PACKING_EXTEND16:
> > return width * 2;
> > case SOC_MBUS_PACKING_1_5X8:
> > return width * 3 / 2;
> > case SOC_MBUS_PACKING_VARIABLE:
> > return 0;
> > }
> > return -EINVAL;
> > }
> >
> > V4L2_PIX_FMT_YUV420 and V4L2_PIX_FMT_YVU420 are classified as
> > SOC_MBUS_PACKING_1_5X8 hence we get width * 3/2
>
> Googling this brings up the entry
>
> {
> .code = V4L2_MBUS_FMT_YUYV8_1_5X8,
> .fmt = {
> .fourcc = V4L2_PIX_FMT_YUV420,
> .name = "YUYV 4:2:0",
> .bits_per_sample = 8,
> .packing = SOC_MBUS_PACKING_1_5X8,
> .order = SOC_MBUS_ORDER_LE,
> .layout = SOC_MBUS_LAYOUT_PACKED,
> },
> }
>
> which matches that you're describing. It doesn't make sense to me, since it at the same time specifies PIX_FMT_YUV420 (which is planar with 3 planes, as documented by include/uapi/linux/videodev2.h), and LAYOUT_PACKED
>
> /**
> * enum soc_mbus_layout - planes layout in memory
> * @SOC_MBUS_LAYOUT_PACKED: color components packed
> * @SOC_MBUS_LAYOUT_PLANAR_2Y_U_V: YUV components stored in 3 planes (4:2:2)
> * @SOC_MBUS_LAYOUT_PLANAR_2Y_C: YUV components stored in a luma and a
> * chroma plane (C plane is half the size
> * of Y plane)
> * @SOC_MBUS_LAYOUT_PLANAR_Y_C: YUV components stored in a luma and a
> * chroma plane (C plane is the same size
> * as Y plane)
> */
> enum soc_mbus_layout {
> SOC_MBUS_LAYOUT_PACKED = 0,
> SOC_MBUS_LAYOUT_PLANAR_2Y_U_V,
> SOC_MBUS_LAYOUT_PLANAR_2Y_C,
> SOC_MBUS_LAYOUT_PLANAR_Y_C,
> };
>
> i.e. non-planar. The code in the driver is handling it as three planes as well, with addresses VB0_BASE_ADDRESS/VB0_BASE_ADDRESS_U/VB0_BASE_ADDRESS_V. Since the planes are separate, there should be no need to have more than 'width' samples per line.
>

I did not invent this, I have just simplified this calculation from
downstream, output values remain same. I have no cameras which can
output V4L2_PIX_FMT_YUV420 or V4L2_PIX_FMT_YVU420 so I cannot test if
this works either. Other YUV and RAW formats were tested on real HW
and work perfectly fine.

> >
> > > > + pix->sizeimage = pix->bytesperline * pix->height;
> > > > }
> > > >
> > > > /*
> > > > @@ -576,20 +564,23 @@ static const struct tegra_vi_ops tegra20_vi_ops = {
> > > > .vi_stop_streaming = tegra20_vi_stop_streaming,
> > > > };
> > > >
> > > > -#define TEGRA20_VIDEO_FMT(MBUS_CODE, BPP, FOURCC) \
> > > > -{ \
> > > > - .code = MEDIA_BUS_FMT_##MBUS_CODE, \
> > > > - .bpp = BPP, \
> > > > - .fourcc = V4L2_PIX_FMT_##FOURCC, \
> > > > +#define TEGRA20_VIDEO_FMT(DATA_TYPE, BIT_WIDTH, MBUS_CODE, BPP, FOURCC) \
> > > > +{ \
> > > > + .img_dt = TEGRA_IMAGE_DT_##DATA_TYPE, \
> > > > + .bit_width = BIT_WIDTH, \
> > > > + .code = MEDIA_BUS_FMT_##MBUS_CODE, \
> > > > + .bpp = BPP, \
> > > > + .fourcc = V4L2_PIX_FMT_##FOURCC, \
> > > > }
> > > >
> > > > static const struct tegra_video_format tegra20_video_formats[] = {
> > > > - TEGRA20_VIDEO_FMT(UYVY8_2X8, 2, UYVY),
> > > > - TEGRA20_VIDEO_FMT(VYUY8_2X8, 2, VYUY),
> > > > - TEGRA20_VIDEO_FMT(YUYV8_2X8, 2, YUYV),
> > > > - TEGRA20_VIDEO_FMT(YVYU8_2X8, 2, YVYU),
> > > > - TEGRA20_VIDEO_FMT(UYVY8_2X8, 1, YUV420),
> > > > - TEGRA20_VIDEO_FMT(UYVY8_2X8, 1, YVU420),
> > > > + /* YUV422 */
> > > > + TEGRA20_VIDEO_FMT(YUV422_8, 16, UYVY8_2X8, 16, UYVY),
> > > > + TEGRA20_VIDEO_FMT(YUV422_8, 16, VYUY8_2X8, 16, VYUY),
> > > > + TEGRA20_VIDEO_FMT(YUV422_8, 16, YUYV8_2X8, 16, YUYV),
> > > > + TEGRA20_VIDEO_FMT(YUV422_8, 16, YVYU8_2X8, 16, YVYU),
> > > > + TEGRA20_VIDEO_FMT(YUV422_8, 16, UYVY8_2X8, 12, YUV420),
> > > > + TEGRA20_VIDEO_FMT(YUV422_8, 16, UYVY8_2X8, 12, YVU420),
> > > > };
> > > >
> > > > const struct tegra_vi_soc tegra20_vi_soc = {
> > > >
> > >
> > >
> > >
> > >
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