linux-kernel - Re: [PATCH 2/2] [WIP]: media: Add Synaptics compressed tiled format

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Message-ID: <CAAFQd5D-eG-1cHvRX2nF0nKv6Zz3vVq6_KJ7HV0zZjADV9v1Zg@mail.gmail.com>
Date:   Tue, 23 Aug 2022 15:05:05 +0900
From:   Tomasz Figa <tfiga@...omium.org>
To:     Hsia-Jun Li <Randy.Li@...aptics.com>
Cc:     Nicolas Dufresne <nicolas@...fresne.ca>,
        dri-devel@...ts.freedesktop.org, maarten.lankhorst@...ux.intel.com,
        mripard@...nel.org, tzimmermann@...e.de, airlied@...ux.ie,
        daniel@...ll.ch, mchehab@...nel.org, hverkuil-cisco@...all.nl,
        ezequiel@...guardiasur.com.ar, sakari.ailus@...ux.intel.com,
        ribalda@...omium.org,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        sebastian.hesselbarth@...il.com, jszhang@...nel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/2] [WIP]: media: Add Synaptics compressed tiled format

On Sat, Aug 20, 2022 at 12:44 AM Hsia-Jun Li <Randy.Li@...aptics.com> wrote:
>
>
>
> On 8/19/22 23:28, Nicolas Dufresne wrote:
> > CAUTION: Email originated externally, do not click links or open attachments unless you recognize the sender and know the content is safe.
> >
> >
> > Le vendredi 19 août 2022 à 02:13 +0300, Laurent Pinchart a écrit :
> >> On Thu, Aug 18, 2022 at 02:33:42PM +0800, Hsia-Jun Li wrote:
> >>> On 8/18/22 14:06, Tomasz Figa wrote:
> >>>> On Tue, Aug 9, 2022 at 1:28 AM Hsia-Jun Li <randy.li@...aptics.com> wrote:
> >>>>>
> >>>>> From: "Hsia-Jun(Randy) Li" <randy.li@...aptics.com>
> >>>>>
> >>>>> The most of detail has been written in the drm.
> >>
> >> This patch still needs a description of the format, which should go to
> >> Documentation/userspace-api/media/v4l/.
> >>
> >>>>> Please notice that the tiled formats here request
> >>>>> one more plane for storing the motion vector metadata.
> >>>>> This buffer won't be compressed, so you can't append
> >>>>> it to luma or chroma plane.
> >>>>
> >>>> Does the motion vector buffer need to be exposed to userspace? Is the
> >>>> decoder stateless (requires userspace to specify the reference frames)
> >>>> or stateful (manages the entire decoding process internally)?
> >>>
> >>> No, users don't need to access them at all. Just they need a different
> >>> dma-heap.
> >>>
> >>> You would only get the stateful version of both encoder and decoder.
> >>
> >> Shouldn't the motion vectors be stored in a separate V4L2 buffer,
> >> submitted through a different queue then ?
> >
> > Imho, I believe these should be invisible to users and pooled separately to
> > reduce the overhead. The number of reference is usually lower then the number of
> > allocated display buffers.
> >
> You can't. The motion vector buffer can't share with the luma and chroma
> data planes, nor the data plane for the compression meta data.

I believe what Nicolas is suggesting is to just keep the MV buffer
handling completely separate from video buffers. Just keep a map
between frame buffer and MV buffer in the driver and use the right
buffer when triggering a decode.

>
> You could consider this as a security requirement(the memory region for
> the MV could only be accessed by the decoder) or hardware limitation.
>
> It is also not very easy to manage such a large buffer that would change
> when the resolution changed.

How does it differ from managing additional planes of video buffers?

Best regards,
Tomasz

> >>
> >>>>> Signed-off-by: Hsia-Jun(Randy) Li <randy.li@...aptics.com>
> >>>>> ---
> >>>>>    drivers/media/v4l2-core/v4l2-common.c | 1 +
> >>>>>    drivers/media/v4l2-core/v4l2-ioctl.c  | 2 ++
> >>>>>    include/uapi/linux/videodev2.h        | 2 ++
> >>>>>    3 files changed, 5 insertions(+)
> >>>>>
> >>>>> diff --git a/drivers/media/v4l2-core/v4l2-common.c b/drivers/media/v4l2-core/v4l2-common.c
> >>>>> index e0fbe6ba4b6c..f645278b3055 100644
> >>>>> --- a/drivers/media/v4l2-core/v4l2-common.c
> >>>>> +++ b/drivers/media/v4l2-core/v4l2-common.c
> >>>>> @@ -314,6 +314,7 @@ const struct v4l2_format_info *v4l2_format_info(u32 format)
> >>>>>                   { .format = V4L2_PIX_FMT_SGBRG12,       .pixel_enc = V4L2_PIXEL_ENC_BAYER, .mem_planes = 1, .comp_planes = 1, .bpp = { 2, 0, 0, 0 }, .hdiv = 1, .vdiv = 1 },
> >>>>>                   { .format = V4L2_PIX_FMT_SGRBG12,       .pixel_enc = V4L2_PIXEL_ENC_BAYER, .mem_planes = 1, .comp_planes = 1, .bpp = { 2, 0, 0, 0 }, .hdiv = 1, .vdiv = 1 },
> >>>>>                   { .format = V4L2_PIX_FMT_SRGGB12,       .pixel_enc = V4L2_PIXEL_ENC_BAYER, .mem_planes = 1, .comp_planes = 1, .bpp = { 2, 0, 0, 0 }, .hdiv = 1, .vdiv = 1 },
> >>>>> +               { .format = V4L2_PIX_FMT_NV12M_V4H1C, .pixel_enc = V4L2_PIXEL_ENC_YUV, .mem_planes = 5, .comp_planes = 2, .bpp = { 1, 2, 0, 0 }, .hdiv = 2, .vdiv = 2, .block_w = { 128, 128 }, .block_h = { 128, 128 } },
> >>>>>           };
> >>>>>           unsigned int i;
> >>>>>
> >>>>> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> >>>>> index e6fd355a2e92..8f65964aff08 100644
> >>>>> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> >>>>> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> >>>>> @@ -1497,6 +1497,8 @@ static void v4l_fill_fmtdesc(struct v4l2_fmtdesc *fmt)
> >>>>>                   case V4L2_PIX_FMT_MT21C:        descr = "Mediatek Compressed Format"; break;
> >>>>>                   case V4L2_PIX_FMT_QC08C:        descr = "QCOM Compressed 8-bit Format"; break;
> >>>>>                   case V4L2_PIX_FMT_QC10C:        descr = "QCOM Compressed 10-bit Format"; break;
> >>>>> +               case V4L2_PIX_FMT_NV12M_V4H1C:  descr = "Synaptics Compressed 8-bit tiled Format";break;
> >>>>> +               case V4L2_PIX_FMT_NV12M_10_V4H3P8C:     descr = "Synaptics Compressed 10-bit tiled Format";break;
> >>>>>                   default:
> >>>>>                           if (fmt->description[0])
> >>>>>                                   return;
> >>>>> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> >>>>> index 01e630f2ec78..7e928cb69e7c 100644
> >>>>> --- a/include/uapi/linux/videodev2.h
> >>>>> +++ b/include/uapi/linux/videodev2.h
> >>>>> @@ -661,6 +661,8 @@ struct v4l2_pix_format {
> >>>>>    #define V4L2_PIX_FMT_NV12MT_16X16 v4l2_fourcc('V', 'M', '1', '2') /* 12  Y/CbCr 4:2:0 16x16 tiles */
> >>>>>    #define V4L2_PIX_FMT_NV12M_8L128      v4l2_fourcc('N', 'A', '1', '2') /* Y/CbCr 4:2:0 8x128 tiles */
> >>>>>    #define V4L2_PIX_FMT_NV12M_10BE_8L128 v4l2_fourcc_be('N', 'T', '1', '2') /* Y/CbCr 4:2:0 10-bit 8x128 tiles */
> >>>>> +#define V4L2_PIX_FMT_NV12M_V4H1C v4l2_fourcc('S', 'Y', '1', '2')   /* 12  Y/CbCr 4:2:0 tiles */
> >>>>> +#define V4L2_PIX_FMT_NV12M_10_V4H3P8C v4l2_fourcc('S', 'Y', '1', '0')   /* 12  Y/CbCr 4:2:0 10-bits tiles */
> >>>>>
> >>>>>    /* Bayer formats - see https://urldefense.proofpoint.com/v2/url?u=http-3A__www.siliconimaging.com_RGB-2520Bayer.htm&d=DwIFaQ&c=7dfBJ8cXbWjhc0BhImu8wVIoUFmBzj1s88r8EGyM0UY&r=P4xb2_7biqBxD4LGGPrSV6j-jf3C3xlR7PXU-mLTeZE&m=lkQiuhx0yMAYHGcW-0WaHlF3e2etMHsu-FoNIBdZILGH6FPigwSAmel2vAdcVLkp&s=JKsBzpb_3u9xv52MaMuT4U3T1pPqcObYkpHDBxvcx_4&e=   */
> >>>>>    #define V4L2_PIX_FMT_SBGGR8  v4l2_fourcc('B', 'A', '8', '1') /*  8  BGBG.. GRGR.. */
> >>
> >
>
> --
> Hsia-Jun(Randy) Li