Subject: Re: [PATCH 1/2] media: cedrus: Fix decoding for some HEVC videos

From: Paul Kocialkowski <[email-masked]>
Date: Wed, 18 Dec 2019 09:40:47 +0100

Hi,

On Fri 13 Dec 19, 17:15, Jernej Skrabec wrote:
> It seems that for some HEVC videos at least one bitstream parsing
> trigger must be called in order to be decoded correctly. There is no
> explanation why this helps, but it was observed that several videos
> with this fix are now decoded correctly and there is no regression with
> others.
> 
> Without this fix, those same videos totally crash HEVC decoder (other
> decoder engines are unaffected). After decoding those problematic
> videos, HEVC decoder always returns only green image (all zeros).
> Only complete HW reset helps.
> 
> This fix is similar to that for H264.

Thanks for the fix, interesting that the same issue shows up on HEVC!
I suspect that Allwinner folks never really tested the engine without
using it for bitstream parsing.

Acked-by: Paul Kocialkowski <[email-masked]>

Cheers,

Paul

> Signed-off-by: Jernej Skrabec <[email-masked]>
> ---
>  .../staging/media/sunxi/cedrus/cedrus_h265.c  | 25 ++++++++++++++++---
>  .../staging/media/sunxi/cedrus/cedrus_regs.h  |  1 +
>  2 files changed, 23 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> index 109d3289418c..5a207f1e137c 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> @@ -7,6 +7,7 @@
>   * Copyright (C) 2018 Bootlin
>   */
>  
> +#include <linux/delay.h>
>  #include <linux/types.h>
>  
>  #include <media/videobuf2-dma-contig.h>
> @@ -283,6 +284,23 @@ static void cedrus_h265_write_scaling_list(struct cedrus_ctx *ctx,
>  		}
>  }
>  
> +static void cedrus_h265_skip_bits(struct cedrus_dev *dev, int num)
> +{
> +	int count = 0;
> +
> +	while (count < num) {
> +		int tmp = min(num - count, 32);
> +
> +		cedrus_write(dev, VE_DEC_H265_TRIGGER,
> +			     VE_DEC_H265_TRIGGER_FLUSH_BITS |
> +			     VE_DEC_H265_TRIGGER_TYPE_N_BITS(tmp));
> +		while (cedrus_read(dev, VE_DEC_H265_STATUS) & VE_DEC_H265_STATUS_VLD_BUSY)
> +			udelay(1);
> +
> +		count += tmp;
> +	}
> +}
> +
>  static void cedrus_h265_setup(struct cedrus_ctx *ctx,
>  			      struct cedrus_run *run)
>  {
> @@ -347,10 +365,9 @@ static void cedrus_h265_setup(struct cedrus_ctx *ctx,
>  
>  	/* Source offset and length in bits. */
>  
> -	reg = slice_params->data_bit_offset;
> -	cedrus_write(dev, VE_DEC_H265_BITS_OFFSET, reg);
> +	cedrus_write(dev, VE_DEC_H265_BITS_OFFSET, 0);
>  
> -	reg = slice_params->bit_size - slice_params->data_bit_offset;
> +	reg = slice_params->bit_size;
>  	cedrus_write(dev, VE_DEC_H265_BITS_LEN, reg);
>  
>  	/* Source beginning and end addresses. */
> @@ -385,6 +402,8 @@ static void cedrus_h265_setup(struct cedrus_ctx *ctx,
>  	/* Initialize bitstream access. */
>  	cedrus_write(dev, VE_DEC_H265_TRIGGER, VE_DEC_H265_TRIGGER_INIT_SWDEC);
>  
> +	cedrus_h265_skip_bits(dev, slice_params->data_bit_offset);
> +
>  	/* Bitstream parameters. */
>  
>  	reg = VE_DEC_H265_DEC_NAL_HDR_NAL_UNIT_TYPE(slice_params->nal_unit_type) |
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_regs.h b/drivers/staging/media/sunxi/cedrus/cedrus_regs.h
> index 0d9449fe2b28..df1cceef8d93 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus_regs.h
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_regs.h
> @@ -424,6 +424,7 @@
>  
>  #define VE_DEC_H265_TRIGGER			(VE_ENGINE_DEC_H265 + 0x34)
>  
> +#define VE_DEC_H265_TRIGGER_TYPE_N_BITS(x)	(((x) & 0x3f) << 8)
>  #define VE_DEC_H265_TRIGGER_STCD_VC1		(0x02 << 4)
>  #define VE_DEC_H265_TRIGGER_STCD_AVS		(0x01 << 4)
>  #define VE_DEC_H265_TRIGGER_STCD_HEVC		(0x00 << 4)
> -- 
> 2.24.0
> 

-- 
Paul Kocialkowski, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com
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