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

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

Hi,

first, thanks you for working on this! I also spend some time working on H264 
and I have some comments below.

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,

I triple checked above address and it should be 0x220. For easier 
implementation later, you might want to add second scaling list address for 
8x8 at 0x210. Then you can do something like:

cedrus_h264_write_sram(dev, CEDRUS_SRAM_H264_SCALING_LIST_8x8_0,
			       scaling->scaling_list_8x8[0],
			       sizeof(scaling->scaling_list_8x8[0]));
cedrus_h264_write_sram(dev, CEDRUS_SRAM_H264_SCALING_LIST_8x8_1,
			       scaling->scaling_list_8x8[3],
			       sizeof(scaling->scaling_list_8x8[0]));
cedrus_h264_write_sram(dev, CEDRUS_SRAM_H264_SCALING_LIST_4x4,
			       scaling->scaling_list_4x4,
			       sizeof(scaling->scaling_list_4x4));

I know that it's not implemented here, just FYI.

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

I think subtracting PHYS_OFFSET breaks driver on H3 boards with 2 GiB of RAM. 
Isn't that unnecessary anyway due to

dev->dev->dma_pfn_offset = PHYS_PFN_OFFSET;

in cedrus_hw.c?

This comment is meant for all PHYS_OFFSET subtracting in this patch.

> +	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);
> +		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);
> +
> +	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++) {

I don't think you have to complicate with two loops here. 
cedrus_h264_write_sram() takes void* and it aligns to 4 anyway. So as long 
input buffer is multiple of 4 (u8[CEDRUS_MAX_REF_IDX] qualifies for that), you 
can use single for loop with "u8 sram_array[CEDRUS_MAX_REF_IDX]". This should 
make code much more readable.

> +			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);
> +			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)

You newer set above flag to buffer so this will be always false.

> +				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);
> +	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);
> +	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);

This one can be inferred from sps->chroma_format_idc.

> +	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);

I really think you should use nal_ref_idc here as it is in specification.  You 
can still fake the data from libva backend. I don't think that any driver 
needs this for anything else than check if it is 0 or not.

> +	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;

You might want to set bit 12 here, which enables active reference picture 
override. However, I'm not completely sure about that.

Best regards,
Jernej

> +	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);
> +
> +	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;
> +	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;
>  	}