Re: [linux-sunxi] [PATCH v2 2/2] media: cedrus: Add H264 decoding support

["Jernej Škrabec" <jernej.skrabec@gmail.com>]

Hi!

Jonas Karlman (in CC) and me managed to solve playback issues with interlaced 
H264 videos.

Please check comments below. 

You can also build and test LibreELEC for H3 from 
https://github.com/jernejsk/LibreELEC.tv/tree/hw_dec_ffmpeg

It has all changes suggested below, except buffer sizes are calculated for 
worst case instead of using formula from CedarX. It also uses Jonas WIP FFmpeg 
patches for Request API. libva-v4l2-request library is not used.

Dne četrtek, 15. november 2018 ob 15:56:50 CET je Maxime Ripard napisal(a):
> Introduce some basic H264 decoding support in cedrus. So far, only the
> baseline profile videos have been tested, and some more advanced features
> used in higher profiles are not even implemented.
> 
> Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
> ---
>  drivers/staging/media/sunxi/cedrus/Makefile   |   3 +-
>  drivers/staging/media/sunxi/cedrus/cedrus.c   |  25 +
>  drivers/staging/media/sunxi/cedrus/cedrus.h   |  35 +-
>  .../staging/media/sunxi/cedrus/cedrus_dec.c   |  11 +
>  .../staging/media/sunxi/cedrus/cedrus_h264.c  | 470 ++++++++++++++++++
>  .../staging/media/sunxi/cedrus/cedrus_hw.c    |   4 +
>  .../staging/media/sunxi/cedrus/cedrus_regs.h  |  63 +++
>  .../staging/media/sunxi/cedrus/cedrus_video.c |   9 +
>  8 files changed, 618 insertions(+), 2 deletions(-)
>  create mode 100644 drivers/staging/media/sunxi/cedrus/cedrus_h264.c
> 
> diff --git a/drivers/staging/media/sunxi/cedrus/Makefile
> b/drivers/staging/media/sunxi/cedrus/Makefile index
> e9dc68b7bcb6..aaf141fc58b6 100644
> --- a/drivers/staging/media/sunxi/cedrus/Makefile
> +++ b/drivers/staging/media/sunxi/cedrus/Makefile
> @@ -1,3 +1,4 @@
>  obj-$(CONFIG_VIDEO_SUNXI_CEDRUS) += sunxi-cedrus.o
> 
> -sunxi-cedrus-y = cedrus.o cedrus_video.o cedrus_hw.o cedrus_dec.o
> cedrus_mpeg2.o +sunxi-cedrus-y = cedrus.o cedrus_video.o cedrus_hw.o
> cedrus_dec.o \ +		 cedrus_mpeg2.o cedrus_h264.o
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus.c
> b/drivers/staging/media/sunxi/cedrus/cedrus.c index
> 82558455384a..627a8c07eb21 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus.c
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus.c
> @@ -40,6 +40,30 @@ static const struct cedrus_control cedrus_controls[] = {
>  		.codec		= CEDRUS_CODEC_MPEG2,
>  		.required	= false,
>  	},
> +	{
> +		.id		= V4L2_CID_MPEG_VIDEO_H264_DECODE_PARAMS,
> +		.elem_size	= sizeof(struct v4l2_ctrl_h264_decode_param),
> +		.codec		= CEDRUS_CODEC_H264,
> +		.required	= true,
> +	},
> +	{
> +		.id		= V4L2_CID_MPEG_VIDEO_H264_SLICE_PARAMS,
> +		.elem_size	= sizeof(struct v4l2_ctrl_h264_slice_param),
> +		.codec		= CEDRUS_CODEC_H264,
> +		.required	= true,
> +	},
> +	{
> +		.id		= V4L2_CID_MPEG_VIDEO_H264_SPS,
> +		.elem_size	= sizeof(struct v4l2_ctrl_h264_sps),
> +		.codec		= CEDRUS_CODEC_H264,
> +		.required	= true,
> +	},
> +	{
> +		.id		= V4L2_CID_MPEG_VIDEO_H264_PPS,
> +		.elem_size	= sizeof(struct v4l2_ctrl_h264_pps),
> +		.codec		= CEDRUS_CODEC_H264,
> +		.required	= true,
> +	},
>  };
> 
>  #define CEDRUS_CONTROLS_COUNT	ARRAY_SIZE(cedrus_controls)
> @@ -277,6 +301,7 @@ static int cedrus_probe(struct platform_device *pdev)
>  	}
> 
>  	dev->dec_ops[CEDRUS_CODEC_MPEG2] = &cedrus_dec_ops_mpeg2;
> +	dev->dec_ops[CEDRUS_CODEC_H264] = &cedrus_dec_ops_h264;
> 
>  	mutex_init(&dev->dev_mutex);
>  	spin_lock_init(&dev->irq_lock);
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus.h
> b/drivers/staging/media/sunxi/cedrus/cedrus.h index
> 781676b55a1b..179c10dcf6a7 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus.h
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus.h
> @@ -30,7 +30,7 @@
> 
>  enum cedrus_codec {
>  	CEDRUS_CODEC_MPEG2,
> -
> +	CEDRUS_CODEC_H264,
>  	CEDRUS_CODEC_LAST,
>  };
> 
> @@ -40,6 +40,12 @@ enum cedrus_irq_status {
>  	CEDRUS_IRQ_OK,
>  };
> 
> +enum cedrus_h264_pic_type {
> +	CEDRUS_H264_PIC_TYPE_FRAME	= 0,
> +	CEDRUS_H264_PIC_TYPE_FIELD,
> +	CEDRUS_H264_PIC_TYPE_MBAFF,
> +};
> +
>  struct cedrus_control {
>  	u32			id;
>  	u32			elem_size;
> @@ -47,6 +53,13 @@ struct cedrus_control {
>  	unsigned char		required:1;
>  };
> 
> +struct cedrus_h264_run {
> +	const struct v4l2_ctrl_h264_decode_param	*decode_param;
> +	const struct v4l2_ctrl_h264_pps			*pps;
> +	const struct v4l2_ctrl_h264_slice_param		*slice_param;
> +	const struct v4l2_ctrl_h264_sps			*sps;
> +};
> +
>  struct cedrus_mpeg2_run {
>  	const struct v4l2_ctrl_mpeg2_slice_params	*slice_params;
>  	const struct v4l2_ctrl_mpeg2_quantization	*quantization;
> @@ -57,12 +70,20 @@ struct cedrus_run {
>  	struct vb2_v4l2_buffer	*dst;
> 
>  	union {
> +		struct cedrus_h264_run	h264;
>  		struct cedrus_mpeg2_run	mpeg2;
>  	};
>  };
> 
>  struct cedrus_buffer {
>  	struct v4l2_m2m_buffer          m2m_buf;
> +
> +	union {
> +		struct {
> +			unsigned int			position;
> +			enum cedrus_h264_pic_type	pic_type;
> +		} h264;
> +	} codec;
>  };
> 
>  struct cedrus_ctx {
> @@ -77,6 +98,17 @@ struct cedrus_ctx {
>  	struct v4l2_ctrl		**ctrls;
> 
>  	struct vb2_buffer		*dst_bufs[VIDEO_MAX_FRAME];
> +
> +	union {
> +		struct {
> +			void		*mv_col_buf;
> +			dma_addr_t	mv_col_buf_dma;
> +			ssize_t		mv_col_buf_field_size;
> +			ssize_t		mv_col_buf_size;
> +			void		*pic_info_buf;
> +			dma_addr_t	pic_info_buf_dma;
> +		} h264;
> +	} codec;
>  };
> 
>  struct cedrus_dec_ops {
> @@ -120,6 +152,7 @@ struct cedrus_dev {
>  };
> 
>  extern struct cedrus_dec_ops cedrus_dec_ops_mpeg2;
> +extern struct cedrus_dec_ops cedrus_dec_ops_h264;
> 
>  static inline void cedrus_write(struct cedrus_dev *dev, u32 reg, u32 val)
>  {
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_dec.c
> b/drivers/staging/media/sunxi/cedrus/cedrus_dec.c index
> 0cfd6036d0cd..b606f07d94ab 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus_dec.c
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_dec.c
> @@ -49,6 +49,17 @@ void cedrus_device_run(void *priv)
>  			V4L2_CID_MPEG_VIDEO_MPEG2_QUANTIZATION);
>  		break;
> 
> +	case V4L2_PIX_FMT_H264_SLICE:
> +		run.h264.decode_param = cedrus_find_control_data(ctx,
> +			V4L2_CID_MPEG_VIDEO_H264_DECODE_PARAMS);
> +		run.h264.pps = cedrus_find_control_data(ctx,
> +			V4L2_CID_MPEG_VIDEO_H264_PPS);
> +		run.h264.slice_param = cedrus_find_control_data(ctx,
> +			V4L2_CID_MPEG_VIDEO_H264_SLICE_PARAMS);
> +		run.h264.sps = cedrus_find_control_data(ctx,
> +			V4L2_CID_MPEG_VIDEO_H264_SPS);
> +		break;
> +
>  	default:
>  		break;
>  	}
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_h264.c
> b/drivers/staging/media/sunxi/cedrus/cedrus_h264.c new file mode 100644
> index 000000000000..5459a936b4b9
> --- /dev/null
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_h264.c
> @@ -0,0 +1,470 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (c) 2013 Jens Kuske <jenskuske@gmail.com>
> + * Copyright (c) 2018 Bootlin
> + */
> +
> +#include <linux/types.h>
> +
> +#include <media/videobuf2-dma-contig.h>
> +
> +#include "cedrus.h"
> +#include "cedrus_hw.h"
> +#include "cedrus_regs.h"
> +
> +enum cedrus_h264_sram_off {
> +	CEDRUS_SRAM_H264_PRED_WEIGHT_TABLE	= 0x000,
> +	CEDRUS_SRAM_H264_FRAMEBUFFER_LIST	= 0x100,
> +	CEDRUS_SRAM_H264_REF_LIST_0		= 0x190,
> +	CEDRUS_SRAM_H264_REF_LIST_1		= 0x199,
> +	CEDRUS_SRAM_H264_SCALING_LIST_8x8	= 0x200,
> +	CEDRUS_SRAM_H264_SCALING_LIST_4x4	= 0x218,
> +};
> +
> +struct cedrus_h264_sram_ref_pic {
> +	__le32	top_field_order_cnt;
> +	__le32	bottom_field_order_cnt;
> +	__le32	frame_info;
> +	__le32	luma_ptr;
> +	__le32	chroma_ptr;
> +	__le32	mv_col_top_ptr;
> +	__le32	mv_col_bot_ptr;
> +	__le32	reserved;
> +} __packed;
> +
> +/* One for the output, 16 for the reference images */
> +#define CEDRUS_H264_FRAME_NUM		17

HW actually supports 18 frames. It would be nice to at least zero out the last 
position.

> +
> +#define CEDRUS_PIC_INFO_BUF_SIZE	(128 * SZ_1K)

I suggest to determine above value according to formula found in CedarX 
source.

> +
> +static void cedrus_h264_write_sram(struct cedrus_dev *dev,
> +				   enum cedrus_h264_sram_off off,
> +				   const void *data, size_t len)
> +{
> +	const u32 *buffer = data;
> +	size_t count = DIV_ROUND_UP(len, 4);
> +
> +	cedrus_write(dev, VE_AVC_SRAM_PORT_OFFSET, off << 2);
> +
> +	do {
> +		cedrus_write(dev, VE_AVC_SRAM_PORT_DATA, *buffer++);
> +	} while (--count);
> +}
> +
> +static dma_addr_t cedrus_h264_mv_col_buf_addr(struct cedrus_ctx *ctx,
> +					      unsigned int position,
> +					      unsigned int field)
> +{
> +	dma_addr_t addr = ctx->codec.h264.mv_col_buf_dma - PHYS_OFFSET;
> +
> +	/* Adjust for the position */
> +	addr += position * ctx->codec.h264.mv_col_buf_field_size * 2;
> +
> +	/* Adjust for the field */
> +	addr += field * ctx->codec.h264.mv_col_buf_field_size;
> +
> +	return addr;
> +}
> +
> +static void cedrus_fill_ref_pic(struct cedrus_ctx *ctx,
> +				struct cedrus_buffer *buf,
> +				unsigned int top_field_order_cnt,
> +				unsigned int bottom_field_order_cnt,
> +				struct cedrus_h264_sram_ref_pic *pic)
> +{
> +	struct vb2_buffer *vbuf = &buf->m2m_buf.vb.vb2_buf;
> +	unsigned int position = buf->codec.h264.position;
> +
> +	pic->top_field_order_cnt = top_field_order_cnt;
> +	pic->bottom_field_order_cnt = bottom_field_order_cnt;
> +	pic->frame_info = buf->codec.h264.pic_type << 8;
> +
> +	pic->luma_ptr = cedrus_buf_addr(vbuf, &ctx->dst_fmt, 0) - PHYS_OFFSET;
> +	pic->chroma_ptr = cedrus_buf_addr(vbuf, &ctx->dst_fmt, 1) - PHYS_OFFSET;
> +	pic->mv_col_top_ptr = cedrus_h264_mv_col_buf_addr(ctx, position, 0);
> +	pic->mv_col_bot_ptr = cedrus_h264_mv_col_buf_addr(ctx, position, 1);
> +}
> +
> +static void cedrus_write_frame_list(struct cedrus_ctx *ctx,
> +				    struct cedrus_run *run)
> +{
> +	struct cedrus_h264_sram_ref_pic pic_list[CEDRUS_H264_FRAME_NUM];
> +	const struct v4l2_ctrl_h264_decode_param *dec_param =
> run->h264.decode_param; +	const struct v4l2_ctrl_h264_slice_param *slice =
> run->h264.slice_param; +	const struct v4l2_ctrl_h264_sps *sps =
> run->h264.sps;
> +	struct vb2_queue *cap_q = &ctx->fh.m2m_ctx->cap_q_ctx.q;
> +	struct cedrus_buffer *output_buf;
> +	struct cedrus_dev *dev = ctx->dev;
> +	unsigned long used_dpbs = 0;
> +	unsigned int position;
> +	unsigned int output = 0;
> +	unsigned int i;
> +
> +	memset(pic_list, 0, sizeof(pic_list));
> +
> +	for (i = 0; i < ARRAY_SIZE(dec_param->dpb); i++) {
> +		const struct v4l2_h264_dpb_entry *dpb = &dec_param->dpb[i];
> +		struct cedrus_buffer *cedrus_buf;
> +		int buf_idx;
> +
> +		if (!(dpb->flags & V4L2_H264_DPB_ENTRY_FLAG_VALID))
> +			continue;
> +
> +		buf_idx = vb2_find_tag(cap_q, dpb->tag, 0);

Field pictures may reference current capture buffer. However, vb2_find_tag won't 
check queued capture buffer tag, so the frame will be skipped and not written 
to the frame list.

This can be solved by:

struct vb2_v4l2_buffer *v4l2_buf = to_vb2_v4l2_buffer(&run->dst->vb2_buf);
...
if (v4l2_buf->tag == dpb->tag)
	buf_idx = v4l2_buf->vb2_buf.index;
else
	buf_idx = vb2_find_tag(cap_q, dpb->tag, 0);


> +		if (buf_idx < 0)
> +			continue;
> +
> +		cedrus_buf = vb2_to_cedrus_buffer(ctx->dst_bufs[buf_idx]);
> +		position = cedrus_buf->codec.h264.position;
> +		used_dpbs |= BIT(position);
> +
> +		if (!(dpb->flags & V4L2_H264_DPB_ENTRY_FLAG_ACTIVE))
> +			continue;
> +
> +		cedrus_fill_ref_pic(ctx, cedrus_buf,
> +				    dpb->top_field_order_cnt,
> +				    dpb->bottom_field_order_cnt,
> +				    &pic_list[position]);
> +
> +		output = max(position, output);
> +	}
> +
> +	position = find_next_zero_bit(&used_dpbs, CEDRUS_H264_FRAME_NUM,
> +				      output);
> +	if (position >= CEDRUS_H264_FRAME_NUM)
> +		position = find_first_zero_bit(&used_dpbs, CEDRUS_H264_FRAME_NUM);

If capture buffer is part of DPB, position is already known.

> +
> +	output_buf = vb2_to_cedrus_buffer(&run->dst->vb2_buf);
> +	output_buf->codec.h264.position = position;
> +
> +	if (slice->flags & V4L2_H264_SLICE_FLAG_FIELD_PIC)
> +		output_buf->codec.h264.pic_type = CEDRUS_H264_PIC_TYPE_FIELD;
> +	else if (sps->flags & V4L2_H264_SPS_FLAG_MB_ADAPTIVE_FRAME_FIELD)
> +		output_buf->codec.h264.pic_type = CEDRUS_H264_PIC_TYPE_MBAFF;
> +	else
> +		output_buf->codec.h264.pic_type = CEDRUS_H264_PIC_TYPE_FRAME;
> +
> +	cedrus_fill_ref_pic(ctx, output_buf,
> +			    dec_param->top_field_order_cnt,
> +			    dec_param->bottom_field_order_cnt,
> +			    &pic_list[position]);
> +
> +	cedrus_h264_write_sram(dev, CEDRUS_SRAM_H264_FRAMEBUFFER_LIST,
> +			       pic_list, sizeof(pic_list));
> +
> +	cedrus_write(dev, VE_H264_OUTPUT_FRAME_IDX, position);
> +}
> +
> +#define CEDRUS_MAX_REF_IDX	32
> +
> +static void _cedrus_write_ref_list(struct cedrus_ctx *ctx,
> +				   struct cedrus_run *run,
> +				   const u8 *ref_list, u8 num_ref,
> +				   enum cedrus_h264_sram_off sram)
> +{
> +	const struct v4l2_ctrl_h264_decode_param *decode = run->h264.decode_param;
> +	struct vb2_queue *cap_q = &ctx->fh.m2m_ctx->cap_q_ctx.q;
> +	struct cedrus_dev *dev = ctx->dev;
> +	u32 sram_array[CEDRUS_MAX_REF_IDX / sizeof(u32)];
> +	unsigned int size, i;
> +
> +	memset(sram_array, 0, sizeof(sram_array));
> +
> +	for (i = 0; i < num_ref; i += 4) {
> +		unsigned int j;
> +
> +		for (j = 0; j < 4; j++) {
> +			const struct v4l2_h264_dpb_entry *dpb;
> +			const struct cedrus_buffer *cedrus_buf;
> +			const struct vb2_v4l2_buffer *ref_buf;
> +			unsigned int position;
> +			int buf_idx;
> +			u8 ref_idx = i + j;
> +			u8 dpb_idx;
> +
> +			if (ref_idx >= num_ref)
> +				break;
> +
> +			dpb_idx = ref_list[ref_idx];
> +			dpb = &decode->dpb[dpb_idx];
> +
> +			if (!(dpb->flags & V4L2_H264_DPB_ENTRY_FLAG_ACTIVE))
> +				continue;
> +
> +			buf_idx = vb2_find_tag(cap_q, dpb->tag, 0);

Same story as above. Capture buffer tag needs to be checked too.

> +			if (buf_idx < 0)
> +				continue;
> +
> +			ref_buf = to_vb2_v4l2_buffer(ctx->dst_bufs[buf_idx]);
> +			cedrus_buf = vb2_v4l2_to_cedrus_buffer(ref_buf);
> +			position = cedrus_buf->codec.h264.position;
> +
> +			sram_array[i] |= position << (j * 8 + 1);
> +			if (ref_buf->field == V4L2_FIELD_BOTTOM)

Above check won't work. Here driver should check if this is "bottom reference" 
which is different as picture field type. We made a hack for PoC code and 
encoded "bottom reference" and "top reference" information in bit 7 and bit 6 
of each ref_list[] element because only 4 bits are actually used.

> +				sram_array[i] |= BIT(j * 8);
> +		}
> +	}
> +
> +	size = min((unsigned int)ALIGN(num_ref, 4), sizeof(sram_array));
> +	cedrus_h264_write_sram(dev, sram, &sram_array, size);
> +}
> +
> +static void cedrus_write_ref_list0(struct cedrus_ctx *ctx,
> +				   struct cedrus_run *run)
> +{
> +	const struct v4l2_ctrl_h264_slice_param *slice = run->h264.slice_param;
> +
> +	_cedrus_write_ref_list(ctx, run,
> +			       slice->ref_pic_list0,
> +			       slice->num_ref_idx_l0_active_minus1 + 1,
> +			       CEDRUS_SRAM_H264_REF_LIST_0);
> +}
> +
> +static void cedrus_write_ref_list1(struct cedrus_ctx *ctx,
> +				   struct cedrus_run *run)
> +{
> +	const struct v4l2_ctrl_h264_slice_param *slice = run->h264.slice_param;
> +
> +	_cedrus_write_ref_list(ctx, run,
> +			       slice->ref_pic_list1,
> +			       slice->num_ref_idx_l1_active_minus1 + 1,
> +			       CEDRUS_SRAM_H264_REF_LIST_1);
> +}
> +
> +static void cedrus_set_params(struct cedrus_ctx *ctx,
> +			      struct cedrus_run *run)
> +{
> +	const struct v4l2_ctrl_h264_slice_param *slice = run->h264.slice_param;
> +	const struct v4l2_ctrl_h264_pps *pps = run->h264.pps;
> +	const struct v4l2_ctrl_h264_sps *sps = run->h264.sps;
> +	struct cedrus_dev *dev = ctx->dev;
> +	dma_addr_t src_buf_addr;
> +	u32 offset = slice->header_bit_size;
> +	u32 len = (slice->size * 8) - offset;
> +	u32 reg;
> +
> +	cedrus_write(dev, 0x220, 0x02000400);

My tests worked well without above line. Do you know if it is really needed? 

> +	cedrus_write(dev, VE_H264_VLD_LEN, len);
> +	cedrus_write(dev, VE_H264_VLD_OFFSET, offset);
> +
> +	src_buf_addr = vb2_dma_contig_plane_dma_addr(&run->src->vb2_buf, 0);
> +	src_buf_addr -= PHYS_OFFSET;
> +	cedrus_write(dev, VE_H264_VLD_END, src_buf_addr + VBV_SIZE - 1);

VBV_SIZE should be replaced with true size aligned to 1024.

This might not be actually relevant for correctness of decoding.

> +	cedrus_write(dev, VE_H264_VLD_ADDR,
> +		     VE_H264_VLD_ADDR_VAL(src_buf_addr) |
> +		     VE_H264_VLD_ADDR_FIRST | VE_H264_VLD_ADDR_VALID |
> +		     VE_H264_VLD_ADDR_LAST);
> +
> +	/*
> +	 * FIXME: Since the bitstream parsing is done in software, and
> +	 * in userspace, this shouldn't be needed anymore. But it
> +	 * turns out that removing it breaks the decoding process,
> +	 * without any clear indication why.
> +	 */
> +	cedrus_write(dev, VE_H264_TRIGGER_TYPE,
> +		     VE_H264_TRIGGER_TYPE_INIT_SWDEC);
> +
> +	if ((slice->slice_type == V4L2_H264_SLICE_TYPE_P) ||
> +	    (slice->slice_type == V4L2_H264_SLICE_TYPE_SP) ||
> +	    (slice->slice_type == V4L2_H264_SLICE_TYPE_B))
> +		cedrus_write_ref_list0(ctx, run);
> +
> +	if (slice->slice_type == V4L2_H264_SLICE_TYPE_B)
> +		cedrus_write_ref_list1(ctx, run);
> +
> +	// picture parameters
> +	reg = 0;
> +	/*
> +	 * FIXME: the kernel headers are allowing the default value to
> +	 * be passed, but the libva doesn't give us that.
> +	 */
> +	reg |= (slice->num_ref_idx_l0_active_minus1 & 0x1f) << 10;
> +	reg |= (slice->num_ref_idx_l1_active_minus1 & 0x1f) << 5;
> +	reg |= (pps->weighted_bipred_idc & 0x3) << 2;
> +	if (pps->flags & V4L2_H264_PPS_FLAG_ENTROPY_CODING_MODE)
> +		reg |= BIT(15);
> +	if (pps->flags & V4L2_H264_PPS_FLAG_WEIGHTED_PRED)
> +		reg |= BIT(4);
> +	if (pps->flags & V4L2_H264_PPS_FLAG_CONSTRAINED_INTRA_PRED)
> +		reg |= BIT(1);
> +	if (pps->flags & V4L2_H264_PPS_FLAG_TRANSFORM_8X8_MODE)
> +		reg |= BIT(0);
> +	cedrus_write(dev, VE_H264_PIC_HDR, reg);
> +
> +	// sequence parameters
> +	reg = BIT(19);
> +	reg |= (sps->pic_width_in_mbs_minus1 & 0xff) << 8;
> +	reg |= sps->pic_height_in_map_units_minus1 & 0xff;
> +	if (sps->flags & V4L2_H264_SPS_FLAG_FRAME_MBS_ONLY)
> +		reg |= BIT(18);
> +	if (sps->flags & V4L2_H264_SPS_FLAG_MB_ADAPTIVE_FRAME_FIELD)
> +		reg |= BIT(17);
> +	if (sps->flags & V4L2_H264_SPS_FLAG_DIRECT_8X8_INFERENCE)
> +		reg |= BIT(16);
> +	cedrus_write(dev, VE_H264_FRAME_SIZE, reg);
> +
> +	// slice parameters
> +	reg = 0;
> +	/*
> +	 * FIXME: This bit marks all the frames as references. This
> +	 * should probably be set based on nal_ref_idc, but the libva
> +	 * doesn't pass that information along, so this is not always
> +	 * available. We should find something else, maybe change the
> +	 * kernel UAPI somehow?
> +	 */
> +	reg |= BIT(12);
> +	reg |= (slice->slice_type & 0xf) << 8;
> +	reg |= slice->cabac_init_idc & 0x3;
> +	reg |= BIT(5);
> +	if (slice->flags & V4L2_H264_SLICE_FLAG_FIELD_PIC)
> +		reg |= BIT(4);
> +	if (slice->flags & V4L2_H264_SLICE_FLAG_BOTTOM_FIELD)
> +		reg |= BIT(3);
> +	if (slice->flags & V4L2_H264_SLICE_FLAG_DIRECT_SPATIAL_MV_PRED)
> +		reg |= BIT(2);
> +	cedrus_write(dev, VE_H264_SLICE_HDR, reg);
> +
> +	reg = 0;

I suggest to always set BIT(12) here (num_ref_idx_active_override_flag) because 
that information is always provided by userspace.

> +	reg |= (slice->num_ref_idx_l0_active_minus1 & 0x1f) << 24;
> +	reg |= (slice->num_ref_idx_l1_active_minus1 & 0x1f) << 16;
> +	reg |= (slice->disable_deblocking_filter_idc & 0x3) << 8;
> +	reg |= (slice->slice_alpha_c0_offset_div2 & 0xf) << 4;
> +	reg |= slice->slice_beta_offset_div2 & 0xf;
> +	cedrus_write(dev, VE_H264_SLICE_HDR2, reg);
> +
> +	reg = 0;
> +	/*
> +	 * FIXME: This bit tells the video engine to use the default
> +	 * quantization matrices. This will obviously need to be
> +	 * changed to support the profiles supporting custom
> +	 * quantization matrices.
> +	 */
> +	reg |= BIT(24);
> +	reg |= (pps->second_chroma_qp_index_offset & 0x3f) << 16;
> +	reg |= (pps->chroma_qp_index_offset & 0x3f) << 8;
> +	reg |= (pps->pic_init_qp_minus26 + 26 + slice->slice_qp_delta) & 0x3f;
> +	cedrus_write(dev, VE_H264_QP_PARAM, reg);
> +
> +	// clear status flags
> +	cedrus_write(dev, VE_H264_STATUS, cedrus_read(dev, VE_H264_STATUS));
> +
> +	// enable int
> +	reg = cedrus_read(dev, VE_H264_CTRL) | 0x7;
> +	cedrus_write(dev, VE_H264_CTRL, reg);
> +}
> +
> +static enum cedrus_irq_status
> +cedrus_h264_irq_status(struct cedrus_ctx *ctx)
> +{
> +	struct cedrus_dev *dev = ctx->dev;
> +	u32 reg = cedrus_read(dev, VE_H264_STATUS) & 0x7;
> +
> +	if (!reg)
> +		return CEDRUS_IRQ_NONE;
> +
> +	if (reg & (BIT(1) | BIT(2)))
> +		return CEDRUS_IRQ_ERROR;
> +
> +	return CEDRUS_IRQ_OK;
> +}
> +
> +static void cedrus_h264_irq_clear(struct cedrus_ctx *ctx)
> +{
> +	struct cedrus_dev *dev = ctx->dev;
> +
> +	cedrus_write(dev, VE_H264_STATUS, GENMASK(2, 0));
> +}
> +
> +static void cedrus_h264_irq_disable(struct cedrus_ctx *ctx)
> +{
> +	struct cedrus_dev *dev = ctx->dev;
> +	u32 reg = cedrus_read(dev, VE_H264_CTRL) & ~GENMASK(2, 0);
> +
> +	cedrus_write(dev, VE_H264_CTRL, reg);
> +}
> +
> +static void cedrus_h264_setup(struct cedrus_ctx *ctx,
> +			      struct cedrus_run *run)
> +{
> +	struct cedrus_dev *dev = ctx->dev;
> +
> +	cedrus_engine_enable(dev, CEDRUS_CODEC_H264);
> +
> +	cedrus_write(dev, VE_H264_SDROT_CTRL, 0);
> +	cedrus_write(dev, VE_H264_EXTRA_BUFFER1,
> +		     ctx->codec.h264.pic_info_buf_dma - PHYS_OFFSET);
> +	cedrus_write(dev, VE_H264_EXTRA_BUFFER2,
> +		     (ctx->codec.h264.pic_info_buf_dma - PHYS_OFFSET) + 0x48000);

 VE_H264_EXTRA_BUFFER2 is actually MB_NEIGHBOR_INFO_ADDR so I would suggest to 
reintroduce the variable "neighbor info buffer" you removed between v1 and v2 
and use it here. According to information I have, it has to be 16 KiB in size, 
but also aligned to 16KiB. Easy solution is to allocate 32 KiB buffer and write 
16K aligned address here.

> +
> +	cedrus_write_frame_list(ctx, run);
> +
> +	cedrus_set_params(ctx, run);
> +}
> +
> +static int cedrus_h264_start(struct cedrus_ctx *ctx)
> +{
> +	struct cedrus_dev *dev = ctx->dev;
> +	unsigned int field_size;
> +	unsigned int mv_col_size;
> +	int ret;
> +
> +	ctx->codec.h264.pic_info_buf =
> +		dma_alloc_coherent(dev->dev, CEDRUS_PIC_INFO_BUF_SIZE,
> +				   &ctx->codec.h264.pic_info_buf_dma,
> +				   GFP_KERNEL);
> +	if (!ctx->codec.h264.pic_info_buf)
> +		return -ENOMEM;
> +
> +	field_size = DIV_ROUND_UP(ctx->src_fmt.width, 16) *
> +		DIV_ROUND_UP(ctx->src_fmt.height, 16) * 32;

Worst case is actually 2 times higher according to CedarX code.

However, better approach would be to multiply with 16 instead of 32 and 
increase this number if:
V4L2_H264_SPS_FLAG_DIRECT_8X8_INFERENCE == 0, by 2x
V4L2_H264_SPS_FLAG_FRAME_MBS_ONLY == 0, by 2x

That way only minimum needed amount of memory is allocated. CedarX code also 
aligns this number to 1024.

Unfortunately, above information is not available here, so this would mean 
that memory allocation have to be done in setup() function, which is not 
ideal...

Best regards,
Jernej

> +	ctx->codec.h264.mv_col_buf_field_size = field_size;
> +
> +	mv_col_size = field_size * 2 * CEDRUS_H264_FRAME_NUM;
> +	ctx->codec.h264.mv_col_buf_size = mv_col_size;
> +	ctx->codec.h264.mv_col_buf = dma_alloc_coherent(dev->dev,
> +							ctx->codec.h264.mv_col_buf_size,
> +							&ctx->codec.h264.mv_col_buf_dma,
> +							GFP_KERNEL);
> +	if (!ctx->codec.h264.mv_col_buf) {
> +		ret = -ENOMEM;
> +		goto err_pic_buf;
> +	}
> +
> +	return 0;
> +
> +err_pic_buf:
> +	dma_free_coherent(dev->dev, CEDRUS_PIC_INFO_BUF_SIZE,
> +			  ctx->codec.h264.pic_info_buf,
> +			  ctx->codec.h264.pic_info_buf_dma);
> +	return ret;
> +}
> +
> +static void cedrus_h264_stop(struct cedrus_ctx *ctx)
> +{
> +	struct cedrus_dev *dev = ctx->dev;
> +
> +	dma_free_coherent(dev->dev, ctx->codec.h264.mv_col_buf_size,
> +			  ctx->codec.h264.mv_col_buf,
> +			  ctx->codec.h264.mv_col_buf_dma);
> +	dma_free_coherent(dev->dev, CEDRUS_PIC_INFO_BUF_SIZE,
> +			  ctx->codec.h264.pic_info_buf,
> +			  ctx->codec.h264.pic_info_buf_dma);
> +}
> +
> +static void cedrus_h264_trigger(struct cedrus_ctx *ctx)
> +{
> +	struct cedrus_dev *dev = ctx->dev;
> +
> +	cedrus_write(dev, VE_H264_TRIGGER_TYPE,
> +		     VE_H264_TRIGGER_TYPE_AVC_SLICE_DECODE);
> +}
> +
> +struct cedrus_dec_ops cedrus_dec_ops_h264 = {
> +	.irq_clear	= cedrus_h264_irq_clear,
> +	.irq_disable	= cedrus_h264_irq_disable,
> +	.irq_status	= cedrus_h264_irq_status,
> +	.setup		= cedrus_h264_setup,
> +	.start		= cedrus_h264_start,
> +	.stop		= cedrus_h264_stop,
> +	.trigger	= cedrus_h264_trigger,
> +};
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_hw.c
> b/drivers/staging/media/sunxi/cedrus/cedrus_hw.c index
> 32adbcbe6175..8e559454ca82 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus_hw.c
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_hw.c
> @@ -46,6 +46,10 @@ int cedrus_engine_enable(struct cedrus_dev *dev, enum
> cedrus_codec codec) reg |= VE_MODE_DEC_MPEG;
>  		break;
> 
> +	case CEDRUS_CODEC_H264:
> +		reg |= VE_MODE_DEC_H264;
> +		break;
> +
>  	default:
>  		return -EINVAL;
>  	}
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_regs.h
> b/drivers/staging/media/sunxi/cedrus/cedrus_regs.h index
> de2d6b6f64bf..6fe9896a506d 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus_regs.h
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_regs.h
> @@ -232,4 +232,67 @@
>  #define VE_DEC_MPEG_ROT_LUMA			(VE_ENGINE_DEC_MPEG + 0xcc)
>  #define VE_DEC_MPEG_ROT_CHROMA			(VE_ENGINE_DEC_MPEG + 0xd0)
> 
> +/*  FIXME: Legacy below. */
> +
> +#define VBV_SIZE                       (1024 * 1024)
> +
> +#define VE_H264_FRAME_SIZE		0x200
> +#define VE_H264_PIC_HDR			0x204
> +#define VE_H264_SLICE_HDR		0x208
> +#define VE_H264_SLICE_HDR2		0x20c
> +#define VE_H264_PRED_WEIGHT		0x210
> +#define VE_H264_QP_PARAM		0x21c
> +#define VE_H264_CTRL			0x220
> +
> +#define VE_H264_TRIGGER_TYPE		0x224
> +#define VE_H264_TRIGGER_TYPE_AVC_SLICE_DECODE	(8 << 0)
> +#define VE_H264_TRIGGER_TYPE_INIT_SWDEC		(7 << 0)
> +
> +#define VE_H264_STATUS			0x228
> +#define VE_H264_CUR_MB_NUM		0x22c
> +
> +#define VE_H264_VLD_ADDR		0x230
> +#define VE_H264_VLD_ADDR_FIRST			BIT(30)
> +#define VE_H264_VLD_ADDR_LAST			BIT(29)
> +#define VE_H264_VLD_ADDR_VALID			BIT(28)
> +#define VE_H264_VLD_ADDR_VAL(x)			(((x) & 0x0ffffff0) | ((x) >> 28))
> +
> +#define VE_H264_VLD_OFFSET		0x234
> +#define VE_H264_VLD_LEN			0x238
> +#define VE_H264_VLD_END			0x23c
> +#define VE_H264_SDROT_CTRL		0x240
> +#define VE_H264_OUTPUT_FRAME_IDX	0x24c
> +#define VE_H264_EXTRA_BUFFER1		0x250
> +#define VE_H264_EXTRA_BUFFER2		0x254
> +#define VE_H264_BASIC_BITS		0x2dc
> +#define VE_AVC_SRAM_PORT_OFFSET		0x2e0
> +#define VE_AVC_SRAM_PORT_DATA		0x2e4
> +
> +#define VE_ISP_INPUT_SIZE		0xa00
> +#define VE_ISP_INPUT_STRIDE		0xa04
> +#define VE_ISP_CTRL			0xa08
> +#define VE_ISP_INPUT_LUMA		0xa78
> +#define VE_ISP_INPUT_CHROMA		0xa7c
> +
> +#define VE_AVC_PARAM			0xb04
> +#define VE_AVC_QP			0xb08
> +#define VE_AVC_MOTION_EST		0xb10
> +#define VE_AVC_CTRL			0xb14
> +#define VE_AVC_TRIGGER			0xb18
> +#define VE_AVC_STATUS			0xb1c
> +#define VE_AVC_BASIC_BITS		0xb20
> +#define VE_AVC_UNK_BUF			0xb60
> +#define VE_AVC_VLE_ADDR			0xb80
> +#define VE_AVC_VLE_END			0xb84
> +#define VE_AVC_VLE_OFFSET		0xb88
> +#define VE_AVC_VLE_MAX			0xb8c
> +#define VE_AVC_VLE_LENGTH		0xb90
> +#define VE_AVC_REF_LUMA			0xba0
> +#define VE_AVC_REF_CHROMA		0xba4
> +#define VE_AVC_REC_LUMA			0xbb0
> +#define VE_AVC_REC_CHROMA		0xbb4
> +#define VE_AVC_REF_SLUMA		0xbb8
> +#define VE_AVC_REC_SLUMA		0xbbc
> +#define VE_AVC_MB_INFO			0xbc0
> +
>  #endif
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_video.c
> b/drivers/staging/media/sunxi/cedrus/cedrus_video.c index
> 293df48326cc..7be2caacddde 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus_video.c
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_video.c
> @@ -37,6 +37,10 @@ static struct cedrus_format cedrus_formats[] = {
>  		.pixelformat	= V4L2_PIX_FMT_MPEG2_SLICE,
>  		.directions	= CEDRUS_DECODE_SRC,
>  	},
> +	{
> +		.pixelformat	= V4L2_PIX_FMT_H264_SLICE,
> +		.directions	= CEDRUS_DECODE_SRC,
> +	},
>  	{
>  		.pixelformat	= V4L2_PIX_FMT_SUNXI_TILED_NV12,
>  		.directions	= CEDRUS_DECODE_DST,
> @@ -100,6 +104,7 @@ static void cedrus_prepare_format(struct v4l2_pix_format
> *pix_fmt)
> 
>  	switch (pix_fmt->pixelformat) {
>  	case V4L2_PIX_FMT_MPEG2_SLICE:
> +	case V4L2_PIX_FMT_H264_SLICE:
>  		/* Zero bytes per line for encoded source. */
>  		bytesperline = 0;
> 
> @@ -451,6 +456,10 @@ static int cedrus_start_streaming(struct vb2_queue *vq,
> unsigned int count) ctx->current_codec = CEDRUS_CODEC_MPEG2;
>  		break;
> 
> +	case V4L2_PIX_FMT_H264_SLICE:
> +		ctx->current_codec = CEDRUS_CODEC_H264;
> +		break;
> +
>  	default:
>  		return -EINVAL;
>  	}