[PATCH v6 4/5] media: mediatek: vcodec: store current vb2 buffer to decode again

[Chen-Yu Tsai]

On Fri, Nov 8, 2024 at 11:32 AM Yunfei Dong <yunfei.dong at mediatek.com> wrote:
>
> All the src vb2 buffer are removed from ready list when STREAMOFF
> capture queue, may remove a non exist vb2 buffer if lat is working

Can you explain how that happens? STREAMOFF supposedly waits for the
current job to finish [1] before touching the queue.

[1] https://elixir.bootlin.com/linux/v6.11.6/source/drivers/media/v4l2-core/v4l2-mem2mem.c#L881

> currently. The driver also need to use current vb2 buffer to decode
> again to wait for enough resource when lat decode error.

This also won't work, since if you remove the only source buffer on
the queue, the core will think that there are no more jobs to do [2],
and won't reschedule anything.

You can work around this by setting the `buffered` flag on the source
queue when you do the retry, and clear it when it succeeds. Set the
flag with v4l2_m2m_set_src_buffered().

[2] https://elixir.bootlin.com/linux/v6.11.6/source/drivers/media/v4l2-core/v4l2-mem2mem.c#L328

> Signed-off-by: Yunfei Dong <yunfei.dong at mediatek.com>
> ---
>  .../vcodec/decoder/mtk_vcodec_dec_drv.h       |  2 ++
>  .../vcodec/decoder/mtk_vcodec_dec_stateless.c | 30 +++++++++++++++----
>  2 files changed, 26 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/media/platform/mediatek/vcodec/decoder/mtk_vcodec_dec_drv.h b/drivers/media/platform/mediatek/vcodec/decoder/mtk_vcodec_dec_drv.h
> index 1fabe8c5b7a4..886fa385e2e6 100644
> --- a/drivers/media/platform/mediatek/vcodec/decoder/mtk_vcodec_dec_drv.h
> +++ b/drivers/media/platform/mediatek/vcodec/decoder/mtk_vcodec_dec_drv.h
> @@ -155,6 +155,7 @@ struct mtk_vcodec_dec_pdata {
>   * @last_decoded_picinfo: pic information get from latest decode
>   * @empty_flush_buf: a fake size-0 capture buffer that indicates flush. Used
>   *                  for stateful decoder.
> + * @cur_src_buffer: current vb2 buffer for the latest decode.
>   * @is_flushing: set to true if flushing is in progress.
>   *
>   * @current_codec: current set input codec, in V4L2 pixel format
> @@ -201,6 +202,7 @@ struct mtk_vcodec_dec_ctx {
>         struct work_struct decode_work;
>         struct vdec_pic_info last_decoded_picinfo;
>         struct v4l2_m2m_buffer empty_flush_buf;
> +       struct vb2_v4l2_buffer *cur_src_buffer;
>         bool is_flushing;
>
>         u32 current_codec;
> diff --git a/drivers/media/platform/mediatek/vcodec/decoder/mtk_vcodec_dec_stateless.c b/drivers/media/platform/mediatek/vcodec/decoder/mtk_vcodec_dec_stateless.c
> index 750f98c1226d..3f94654ebc73 100644
> --- a/drivers/media/platform/mediatek/vcodec/decoder/mtk_vcodec_dec_stateless.c
> +++ b/drivers/media/platform/mediatek/vcodec/decoder/mtk_vcodec_dec_stateless.c
> @@ -324,7 +324,8 @@ static void mtk_vdec_worker(struct work_struct *work)
>         struct mtk_vcodec_dec_ctx *ctx =
>                 container_of(work, struct mtk_vcodec_dec_ctx, decode_work);
>         struct mtk_vcodec_dec_dev *dev = ctx->dev;
> -       struct vb2_v4l2_buffer *vb2_v4l2_src;
> +       struct vb2_v4l2_buffer *vb2_v4l2_src = ctx->cur_src_buffer;
> +       struct vb2_v4l2_buffer *vb2_v4l2_dst;
>         struct vb2_buffer *vb2_src;
>         struct mtk_vcodec_mem *bs_src;
>         struct mtk_video_dec_buf *dec_buf_src;
> @@ -333,7 +334,7 @@ static void mtk_vdec_worker(struct work_struct *work)
>         bool res_chg = false;
>         int ret;
>
> -       vb2_v4l2_src = v4l2_m2m_next_src_buf(ctx->m2m_ctx);
> +       vb2_v4l2_src = vb2_v4l2_src ? vb2_v4l2_src : v4l2_m2m_src_buf_remove(ctx->m2m_ctx);
>         if (!vb2_v4l2_src) {
>                 v4l2_m2m_job_finish(dev->m2m_dev_dec, ctx->m2m_ctx);
>                 mtk_v4l2_vdec_dbg(1, ctx, "[%d] no available source buffer", ctx->id);
> @@ -385,12 +386,29 @@ static void mtk_vdec_worker(struct work_struct *work)
>             ctx->current_codec == V4L2_PIX_FMT_VP8_FRAME) {
>                 if (src_buf_req)
>                         v4l2_ctrl_request_complete(src_buf_req, &ctx->ctrl_hdl);
> -               v4l2_m2m_buf_done_and_job_finish(dev->m2m_dev_dec, ctx->m2m_ctx, state);
> -       } else {
> -               if (ret != -EAGAIN)
> -                       v4l2_m2m_src_buf_remove(ctx->m2m_ctx);
> +               vb2_v4l2_dst = v4l2_m2m_dst_buf_remove(ctx->m2m_ctx);
> +               v4l2_m2m_buf_done(vb2_v4l2_dst, state);
> +               v4l2_m2m_buf_done(vb2_v4l2_src, state);
> +
>                 v4l2_m2m_job_finish(dev->m2m_dev_dec, ctx->m2m_ctx);
> +               return;
>         }
> +
> +       /*
> +        * If each codec return -EAGAIN to decode again, need to backup current source
> +        * buffer, then the driver will get this buffer next time.
> +        *
> +        * If each codec decode error, must to set buffer done with error status for
> +        * this buffer have been removed from ready list.
> +        */
> +       ctx->cur_src_buffer = (ret != -EAGAIN) ? NULL : vb2_v4l2_src;
> +       if (ret && ret != -EAGAIN) {
> +               if (src_buf_req)
> +                       v4l2_ctrl_request_complete(src_buf_req, &ctx->ctrl_hdl);
> +               v4l2_m2m_buf_done(vb2_v4l2_src, state);
> +       }
> +
> +       v4l2_m2m_job_finish(dev->m2m_dev_dec, ctx->m2m_ctx);
>  }
>
>  static void vb2ops_vdec_stateless_buf_queue(struct vb2_buffer *vb)
> --
> 2.46.0
>