linux-kernel - Re: [PATCH v7, 05/15] media: mtk-vcodec: Call v4l2_m2m_set_dst

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Date:   Tue, 01 Mar 2022 13:50:03 -0500
From:   Nicolas Dufresne <nicolas@...fresne.ca>
To:     Yunfei Dong <yunfei.dong@...iatek.com>,
        Alexandre Courbot <acourbot@...omium.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Tzung-Bi Shih <tzungbi@...omium.org>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Benjamin Gaignard <benjamin.gaignard@...labora.com>,
        Tiffany Lin <tiffany.lin@...iatek.com>,
        Andrew-CT Chen <andrew-ct.chen@...iatek.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Tomasz Figa <tfiga@...gle.com>
Cc:     George Sun <george.sun@...iatek.com>,
        Xiaoyong Lu <xiaoyong.lu@...iatek.com>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Fritz Koenig <frkoenig@...omium.org>,
        Dafna Hirschfeld <dafna.hirschfeld@...labora.com>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Irui Wang <irui.wang@...iatek.com>,
        Steve Cho <stevecho@...omium.org>, linux-media@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, srv_heupstream@...iatek.com,
        linux-mediatek@...ts.infradead.org,
        Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH v7, 05/15] media: mtk-vcodec: Call
 v4l2_m2m_set_dst_buffered() set capture buffer buffered

Le mercredi 23 février 2022 à 11:39 +0800, Yunfei Dong a écrit :
> lat thread: output queue      \
>                                -> lat hardware -> lat trans buffer
>             lat trans buffer  /
> 
> core thread: capture queue     \
>                                 ->core hardware -> capture queue
>              lat trans buffer  /
> 
> Lat and core work in different thread, setting capture buffer buffered.

... so that output queue buffers (bitstream) can be process regardless if there
is available capture buffers.

I have concerns around the usefulness of running a dedicated thread to drive the
lat and the core blocks. Having 3 threads (counting the m2m worker thread) here
increase the complexity. The hardware is asynchronous by definition. I think
this patch will go away after a proper rework of the driver thread model here.

> 
> Signed-off-by: Yunfei Dong <yunfei.dong@...iatek.com>
> ---
>  drivers/media/platform/mtk-vcodec/mtk_vcodec_dec_stateless.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/media/platform/mtk-vcodec/mtk_vcodec_dec_stateless.c b/drivers/media/platform/mtk-vcodec/mtk_vcodec_dec_stateless.c
> index 5aebf88f997b..23a154c4e321 100644
> --- a/drivers/media/platform/mtk-vcodec/mtk_vcodec_dec_stateless.c
> +++ b/drivers/media/platform/mtk-vcodec/mtk_vcodec_dec_stateless.c
> @@ -314,6 +314,9 @@ static void mtk_init_vdec_params(struct mtk_vcodec_ctx *ctx)
>  	src_vq = v4l2_m2m_get_vq(ctx->m2m_ctx,
>  				 V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE);
>  
> +	if (ctx->dev->vdec_pdata->hw_arch != MTK_VDEC_PURE_SINGLE_CORE)
> +		v4l2_m2m_set_dst_buffered(ctx->m2m_ctx, 1);
> +
>  	/* Support request api for output plane */
>  	src_vq->supports_requests = true;
>  	src_vq->requires_requests = true;