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SubjectRe: [PATCH 1/2] media: cedrus: Fix decoding for some HEVC videos
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 <paul.kocialkowski@bootlin.com>

Cheers,

Paul

> Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
> ---
> .../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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