linux-kernel - Re: [PATCH 2/2] media: cedrus: Allow using the current dst buffer as reference

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Date:   Wed, 9 Jan 2019 15:29:44 +0100
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Paul Kocialkowski <paul.kocialkowski@...tlin.com>,
        linux-media@...r.kernel.org, devel@...verdev.osuosl.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-sunxi@...glegroups.com
Cc:     Maxime Ripard <maxime.ripard@...tlin.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Chen-Yu Tsai <wens@...e.org>, Randy Li <ayaka@...lik.info>,
        Ezequiel Garcia <ezequiel@...labora.com>,
        Tomasz Figa <tfiga@...omium.org>,
        Alexandre Courbot <acourbot@...omium.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH 2/2] media: cedrus: Allow using the current dst buffer as
 reference

On 01/09/19 15:19, Paul Kocialkowski wrote:
> It was reported that some cases of interleaved video decoding require
> using the current destination buffer as a reference. However, this is
> no longer possible after the move to vb2_find_timestamp because only
> dequeued and done buffers are considered.
> 
> Add a helper in our driver that also considers the current destination
> buffer before resorting to vb2_find_timestamp and use it in MPEG-2.

This patch looks good, but can you also add checks to handle the case
when no buffer with the given timestamp was found? Probably should be done
in a third patch.

I suspect the driver will crash if an unknown timestamp is passed on to the
driver. I would really like to see that corner case fixed.

Regards,

	Hans

> 
> Signed-off-by: Paul Kocialkowski <paul.kocialkowski@...tlin.com>
> ---
>  drivers/staging/media/sunxi/cedrus/cedrus_dec.c   | 13 +++++++++++++
>  drivers/staging/media/sunxi/cedrus/cedrus_dec.h   |  2 ++
>  drivers/staging/media/sunxi/cedrus/cedrus_mpeg2.c | 10 ++++++----
>  3 files changed, 21 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_dec.c b/drivers/staging/media/sunxi/cedrus/cedrus_dec.c
> index 443fb037e1cf..2c295286766c 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus_dec.c
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_dec.c
> @@ -22,6 +22,19 @@
>  #include "cedrus_dec.h"
>  #include "cedrus_hw.h"
>  
> +int cedrus_reference_index_find(struct vb2_queue *queue,
> +				struct vb2_buffer *vb2_buf, u64 timestamp)
> +{
> +	/*
> +	 * Allow using the current capture buffer as reference, which can occur
> +	 * for field-coded pictures.
> +	 */
> +	if (vb2_buf->timestamp == timestamp)
> +		return vb2_buf->index;
> +	else
> +		return vb2_find_timestamp(queue, timestamp, 0);
> +}
> +
>  void cedrus_device_run(void *priv)
>  {
>  	struct cedrus_ctx *ctx = priv;
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_dec.h b/drivers/staging/media/sunxi/cedrus/cedrus_dec.h
> index d1ae7903677b..8d0fc248220f 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus_dec.h
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_dec.h
> @@ -16,6 +16,8 @@
>  #ifndef _CEDRUS_DEC_H_
>  #define _CEDRUS_DEC_H_
>  
> +int cedrus_reference_index_find(struct vb2_queue *queue,
> +				struct vb2_buffer *vb2_buf, u64 timestamp);
>  void cedrus_device_run(void *priv);
>  
>  #endif
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_mpeg2.c b/drivers/staging/media/sunxi/cedrus/cedrus_mpeg2.c
> index cb45fda9aaeb..81c66a8aa1ac 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus_mpeg2.c
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_mpeg2.c
> @@ -10,6 +10,7 @@
>  #include <media/videobuf2-dma-contig.h>
>  
>  #include "cedrus.h"
> +#include "cedrus_dec.h"
>  #include "cedrus_hw.h"
>  #include "cedrus_regs.h"
>  
> @@ -159,8 +160,8 @@ static void cedrus_mpeg2_setup(struct cedrus_ctx *ctx, struct cedrus_run *run)
>  	cedrus_write(dev, VE_DEC_MPEG_PICBOUNDSIZE, reg);
>  
>  	/* Forward and backward prediction reference buffers. */
> -	forward_idx = vb2_find_timestamp(cap_q,
> -					 slice_params->forward_ref_ts, 0);
> +	forward_idx = cedrus_reference_index_find(cap_q, &run->dst->vb2_buf,
> +						  slice_params->forward_ref_ts);
>  
>  	fwd_luma_addr = cedrus_dst_buf_addr(ctx, forward_idx, 0);
>  	fwd_chroma_addr = cedrus_dst_buf_addr(ctx, forward_idx, 1);
> @@ -168,8 +169,9 @@ static void cedrus_mpeg2_setup(struct cedrus_ctx *ctx, struct cedrus_run *run)
>  	cedrus_write(dev, VE_DEC_MPEG_FWD_REF_LUMA_ADDR, fwd_luma_addr);
>  	cedrus_write(dev, VE_DEC_MPEG_FWD_REF_CHROMA_ADDR, fwd_chroma_addr);
>  
> -	backward_idx = vb2_find_timestamp(cap_q,
> -					  slice_params->backward_ref_ts, 0);
> +	backward_idx = cedrus_reference_index_find(cap_q, &run->dst->vb2_buf,
> +						   slice_params->backward_ref_ts);
> +
>  	bwd_luma_addr = cedrus_dst_buf_addr(ctx, backward_idx, 0);
>  	bwd_chroma_addr = cedrus_dst_buf_addr(ctx, backward_idx, 1);
>  
>