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SubjectRe: [PATCH v2 for 5.4 1/4] media: hantro: Fix s_fmt for dynamic resolution changes
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On 11/8/19 11:19 AM, Boris Brezillon wrote:
> On Mon, 7 Oct 2019 14:45:02 -0300
> Ezequiel Garcia <ezequiel@collabora.com> wrote:
>
>> Commit 953aaa1492c53 ("media: rockchip/vpu: Prepare things to support decoders")
>> changed the conditions under S_FMT was allowed for OUTPUT
>> CAPTURE buffers.
>>
>> However, and according to the mem-to-mem stateless decoder specification,
>> in order to support dynamic resolution changes, S_FMT should be allowed
>> even if OUTPUT buffers have been allocated.
>>
>> Relax decoder S_FMT restrictions on OUTPUT buffers, allowing a resolution
>> modification, provided the pixel format stays the same.
>>
>> Tested on RK3288 platforms using ChromiumOS Video Decode/Encode Accelerator Unittests.
>>
>> Fixes: 953aaa1492c53 ("media: rockchip/vpu: Prepare things to support decoders")
>> Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
>> --
>> v2:
>> * Call try_fmt_out before using the format,
>> pointed out by Philipp.
>>
>> drivers/staging/media/hantro/hantro_v4l2.c | 28 +++++++++++++++-------
>> 1 file changed, 19 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/staging/media/hantro/hantro_v4l2.c b/drivers/staging/media/hantro/hantro_v4l2.c
>> index 3dae52abb96c..586d243cc3cc 100644
>> --- a/drivers/staging/media/hantro/hantro_v4l2.c
>> +++ b/drivers/staging/media/hantro/hantro_v4l2.c
>> @@ -367,19 +367,26 @@ vidioc_s_fmt_out_mplane(struct file *file, void *priv, struct v4l2_format *f)
>> {
>> struct v4l2_pix_format_mplane *pix_mp = &f->fmt.pix_mp;
>> struct hantro_ctx *ctx = fh_to_ctx(priv);
>> + struct vb2_queue *vq = v4l2_m2m_get_vq(ctx->fh.m2m_ctx, f->type);
>> const struct hantro_fmt *formats;
>> unsigned int num_fmts;
>> - struct vb2_queue *vq;
>> int ret;
>>
>> - /* Change not allowed if queue is busy. */
>> - vq = v4l2_m2m_get_vq(ctx->fh.m2m_ctx, f->type);
>> - if (vb2_is_busy(vq))
>> - return -EBUSY;
>> + ret = vidioc_try_fmt_out_mplane(file, priv, f);
>> + if (ret)
>> + return ret;
>>
>> if (!hantro_is_encoder_ctx(ctx)) {
>> struct vb2_queue *peer_vq;
>>
>> + /*
>> + * In other to support dynamic resolution change,
>
> ^ order
>
>> + * the decoder admits a resolution change, as long
>> + * as the pixelformat remains. Can't be done if streaming.
>> + */
>> + if (vb2_is_streaming(vq) || (vb2_is_busy(vq) &&
>> + pix_mp->pixelformat != ctx->src_fmt.pixelformat))
>> + return -EBUSY;
>
> Sorry to chime in only now, but I'm currently looking at the VP9 spec
> and it seems the resolution is allowed to change dynamically [1] (I
> guess the same applies to VP8). IIU the spec correctly, coded frames
> using the new resolution can reference decoded frames using the old
> one (can be higher or lower res BTW). If we force a streamoff to change
> the resolution (as seems to be the case here), we'll lose those ref
> frames (see the hantro_return_bufs() in stop streaming), right?
> Hans, Tomasz, any idea how this dynamic resolution change could/should
> be supported?

As Tomasz also mentioned, supporting this is much more work, and probably
requires new streaming ioctls.

In the meantime I think this patch is fine (with the typo fixed, I can do
that), so is it OK if I merge this?

Regards,

Hans

>
>> /*
>> * Since format change on the OUTPUT queue will reset
>> * the CAPTURE queue, we can't allow doing so
>> @@ -389,12 +396,15 @@ vidioc_s_fmt_out_mplane(struct file *file, void *priv, struct v4l2_format *f)
>> V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE);
>> if (vb2_is_busy(peer_vq))
>> return -EBUSY;
>> + } else {
>> + /*
>> + * The encoder doesn't admit a format change if
>> + * there are OUTPUT buffers allocated.
>> + */
>> + if (vb2_is_busy(vq))
>> + return -EBUSY;
>> }
>>
>> - ret = vidioc_try_fmt_out_mplane(file, priv, f);
>> - if (ret)
>> - return ret;
>> -
>> formats = hantro_get_formats(ctx, &num_fmts);
>> ctx->vpu_src_fmt = hantro_find_format(formats, num_fmts,
>> pix_mp->pixelformat);
>
> [1] Section "5.16 Reference frame scaling" of
> https://storage.googleapis.com/downloads.webmproject.org/docs/vp9/vp9-bitstream-specification-v0.6-20160331-draft.pdf
>

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