Re: [PATCH v4 5/7] media: mediatek: vcodec: store source vb2 buffer

["Yunfei Dong (董云飞)" <Yunfei.Dong@mediatek.com>]

Hi Sebastian,

Thanks for your suggestion.
On Fri, 2024-08-23 at 16:14 +0200, Sebastian Fricke wrote:
> Hey Yunfei,
> 
> On 07.08.2024 16:24, Yunfei Dong wrote:
> > Store the current vb2 buffer when lat need to decode again.
> > Then lat work can get the same vb2 buffer directly next time.
> 
> I would reword this with:
> 
> Store the current source buffer in the specific data for the IC. When
> the LAT needs to retry a decode it can pick that buffer directly.
> 
> ---
> 
> Additionally, this is not a good commit description as you just say
> what
> you do, but you don't say WHY this needs to happen, why is it
> necessary?
> What does it improve, is this a preparation patch for another, a fix
> for
> something or an improvement of performance?
> 
> 
> more below...
> 
> > 
> > Signed-off-by: Yunfei Dong <yunfei.dong@mediatek.com>
> > ---
> > .../mediatek/vcodec/decoder/mtk_vcodec_dec_drv.h      |  2 ++
> > .../vcodec/decoder/mtk_vcodec_dec_stateless.c         | 11
> > ++++++++---
> > 2 files changed, 10 insertions(+), 3 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..0817be73f8e0 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.
> > + * @last_vb2_v4l2_src: the backup of current source buffer.
> 
> I think last is confusing in this context especially as there is for
> example in the m2m_ctx:
>   * @last_src_buf: indicate the last source buffer for draining
>   * @next_buf_last: next capture queud buffer will be tagged as last
> or:
>   * v4l2_m2m_last_buf() - return last buffer from the list of ready
> buffers
> 
> I think a better name would be:
> 
>   * @cur_src_buf: current source buffer with the bitstream data 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 *last_vb2_v4l2_src;
> 
> Likewise here:
> 
> struct vb2_v4l2_buffer *cur_src_buf;
> 
> > 	bool is_flushing;
> > 
> > 	u32 current_codec;
> > diff --git
> > a/drivers/media/platform/mediatek/vcodec/decoder/mtk_vcodec_dec_sta
> > teless.c
> > b/drivers/media/platform/mediatek/vcodec/decoder/mtk_vcodec_dec_sta
> > teless.c
> > index 2a7e4fe24ed3..8aa379872ddc 100644
> > ---
> > a/drivers/media/platform/mediatek/vcodec/decoder/mtk_vcodec_dec_sta
> > teless.c
> > +++
> > b/drivers/media/platform/mediatek/vcodec/decoder/mtk_vcodec_dec_sta
> > teless.c
> > @@ -320,7 +320,7 @@ 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->last_vb2_v4l2_src;
> 
> And here:
> 
> struct vb2_v4l2_buffer *vb2_v4l2_src = ctx->cur_src_buf;
> 
> > 	struct vb2_buffer *vb2_src;
> > 	struct mtk_vcodec_mem *bs_src;
> > 	struct mtk_video_dec_buf *dec_buf_src;
> > @@ -329,7 +329,7 @@ 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_next_src_buf(ctx->m2m_ctx);
> 
> Please add a comment above this line that explains why this search
> can
> be made, explaining why this buffer is still valid in this call and
> when
> we pick the next source buffer.
> 

As the commit wrote, if the driver need to decoder again, need to use
the last remove source buffer to decode again, not to get one new.

Regards,
Yunfei Dong
> Regards,
> Sebastian Fricke
> 
> > 	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);
> > @@ -383,8 +383,13 @@ static void mtk_vdec_worker(struct work_struct
> > *work)
> > 			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)
> > +		if (ret != -EAGAIN) {
> > 			v4l2_m2m_src_buf_remove(ctx->m2m_ctx);
> > +			ctx->last_vb2_v4l2_src = NULL;
> > +		} else {
> > +			ctx->last_vb2_v4l2_src = vb2_v4l2_src;
> > +		}
> > +
> > 		v4l2_m2m_job_finish(dev->m2m_dev_dec, ctx->m2m_ctx);
> > 	}
> > }
> > -- 
> > 2.46.0
> > 
> > 
> 
>