linux-kernel - Re: [PATCH 7/8] media: cedrus: Add support for holding capture buffer

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Message-ID: <f105990c-e059-6bdd-433f-074388e3a2dc@xs4all.nl>
Date:   Thu, 29 Aug 2019 13:23:29 +0200
From:   Hans Verkuil <hverkuil-cisco@...all.nl>
To:     Jernej Skrabec <jernej.skrabec@...l.net>, mchehab@...nel.org,
        paul.kocialkowski@...tlin.com, mripard@...nel.org
Cc:     pawel@...iak.com, m.szyprowski@...sung.com,
        kyungmin.park@...sung.com, tfiga@...omium.org, wens@...e.org,
        acourbot@...omium.org, gregkh@...uxfoundation.org,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        devel@...verdev.osuosl.org, linux-arm-kernel@...ts.infradead.org,
        ezequiel@...labora.com, jonas@...boo.se
Subject: Re: [PATCH 7/8] media: cedrus: Add support for holding capture buffer

On 8/22/19 9:44 PM, Jernej Skrabec wrote:
> When frame contains multiple slices and driver works in slice mode, it's
> more efficient to hold capture buffer in queue until all slices of a
> same frame are decoded.
> 
> Add support for that to Cedrus driver by exposing and implementing
> V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF capability.
> 
> Signed-off-by: Jernej Skrabec <jernej.skrabec@...l.net>
> ---
>  drivers/staging/media/sunxi/cedrus/cedrus_dec.c   | 9 +++++++++
>  drivers/staging/media/sunxi/cedrus/cedrus_hw.c    | 8 +++++---
>  drivers/staging/media/sunxi/cedrus/cedrus_video.c | 1 +
>  3 files changed, 15 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_dec.c b/drivers/staging/media/sunxi/cedrus/cedrus_dec.c
> index d7b54accfe83..68462b99750e 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus_dec.c
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_dec.c
> @@ -31,6 +31,14 @@ void cedrus_device_run(void *priv)
>  
>  	run.src = v4l2_m2m_next_src_buf(ctx->fh.m2m_ctx);
>  	run.dst = v4l2_m2m_next_dst_buf(ctx->fh.m2m_ctx);
> +
> +	if (v4l2_m2m_release_capture_buf(run.src, run.dst)) {
> +		v4l2_m2m_dst_buf_remove(ctx->fh.m2m_ctx);
> +		v4l2_m2m_buf_done(run.dst, VB2_BUF_STATE_DONE);
> +		run.dst = v4l2_m2m_next_dst_buf(ctx->fh.m2m_ctx);
> +	}
> +	run.dst->is_held = run.src->flags & V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF;
> +
>  	run.first_slice =
>  		run.src->vb2_buf.timestamp != run.dst->vb2_buf.timestamp;
>  
> @@ -46,6 +54,7 @@ void cedrus_device_run(void *priv)
>  			V4L2_CID_MPEG_VIDEO_MPEG2_SLICE_PARAMS);
>  		run.mpeg2.quantization = cedrus_find_control_data(ctx,
>  			V4L2_CID_MPEG_VIDEO_MPEG2_QUANTIZATION);
> +		run.dst->is_held = false;
>  		break;
>  
>  	case V4L2_PIX_FMT_H264_SLICE:
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_hw.c b/drivers/staging/media/sunxi/cedrus/cedrus_hw.c
> index a942cd9bed57..99fedec80224 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus_hw.c
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_hw.c
> @@ -122,7 +122,7 @@ static irqreturn_t cedrus_irq(int irq, void *data)
>  	dev->dec_ops[ctx->current_codec]->irq_clear(ctx);
>  
>  	src_buf = v4l2_m2m_src_buf_remove(ctx->fh.m2m_ctx);
> -	dst_buf = v4l2_m2m_dst_buf_remove(ctx->fh.m2m_ctx);
> +	dst_buf = v4l2_m2m_next_dst_buf(ctx->fh.m2m_ctx);
>  
>  	if (!src_buf || !dst_buf) {
>  		v4l2_err(&dev->v4l2_dev,
> @@ -136,8 +136,10 @@ static irqreturn_t cedrus_irq(int irq, void *data)
>  		state = VB2_BUF_STATE_DONE;
>  
>  	v4l2_m2m_buf_done(src_buf, state);
> -	v4l2_m2m_buf_done(dst_buf, state);
> -
> +	if (!dst_buf->is_held) {
> +		v4l2_m2m_dst_buf_remove(ctx->fh.m2m_ctx);
> +		v4l2_m2m_buf_done(dst_buf, state);
> +	}
>  	v4l2_m2m_job_finish(ctx->dev->m2m_dev, ctx->fh.m2m_ctx);
>  
>  	return IRQ_HANDLED;
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_video.c b/drivers/staging/media/sunxi/cedrus/cedrus_video.c
> index eeee3efd247b..5153b2bba21e 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus_video.c
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_video.c
> @@ -515,6 +515,7 @@ int cedrus_queue_init(void *priv, struct vb2_queue *src_vq,
>  	src_vq->type = V4L2_BUF_TYPE_VIDEO_OUTPUT;
>  	src_vq->io_modes = VB2_MMAP | VB2_DMABUF;
>  	src_vq->drv_priv = ctx;
> +	src_vq->subsystem_flags = VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF;

This isn't quite right: this flag should only be set for formats that support
slicing. So cedrus_s_fmt_vid_out() should set this for H264, but clear it for
MPEG2.

Looking at the cedrus code it seems that it does not set an initial default output
format after opening the video device. This seems wrong to me. If it did set a
default output format, then src_vq->subsystem_flags should set this flag corresponding
to the default output format.

>  	src_vq->buf_struct_size = sizeof(struct cedrus_buffer);
>  	src_vq->min_buffers_needed = 1;
>  	src_vq->ops = &cedrus_qops;
> 

Regards,

	Hans