linux-kernel - Re: [PATCH v2 04/10] media: hantro: Fix H264 motion vector buffer offset

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Date:   Thu, 31 Oct 2019 10:47:34 +0100
From:   Boris Brezillon <boris.brezillon@...labora.com>
To:     Jonas Karlman <jonas@...boo.se>
Cc:     Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Ezequiel Garcia <ezequiel@...labora.com>,
        Hans Verkuil <hverkuil@...all.nl>,
        Tomasz Figa <tfiga@...omium.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 04/10] media: hantro: Fix H264 motion vector buffer
 offset

On Tue, 29 Oct 2019 01:24:49 +0000
Jonas Karlman <jonas@...boo.se> wrote:

> A decoded 8-bit 4:2:0 frame need memory for up to 448 bytes per
> macroblock and is laid out in memory as follow:
> 
> +---------------------------+
> | Y-plane   256 bytes x MBs |
> +---------------------------+
> | UV-plane  128 bytes x MBs |
> +---------------------------+
> | MV buffer  64 bytes x MBs |
> +---------------------------+

Would be great to also have this sort of diagram as a comment in the
code.

> 
> The motion vector buffer offset is currently correct for 4:2:0 because the
> extra space for motion vectors is overallocated with an extra 64 bytes x MBs.
> 
> Wrong offset for both destination and motion vector buffer are used
> for the bottom field of field encoded content, wrong offset is
> also used for 4:0:0 (monochrome) content.
> 
> Fix this by setting the motion vector address to the expected 384 bytes x MBs
> offset for 4:2:0 and 256 bytes x MBs offset for 4:0:0 content.
> 
> Also use correct destination and motion vector buffer offset
> for the bottom field of field encoded content.
> 
> While at it also extend the check for 4:0:0 (monochrome) to include an
> additional check for High Profile (100).
> 
> Fixes: dea0a82f3d22 ("media: hantro: Add support for H264 decoding on G1")
> Signed-off-by: Jonas Karlman <jonas@...boo.se>

Reviewed-by: Boris Brezillon <boris.brezillon@...labora.com>

Just 2 nitpicks (see below).

> ---
> Changes in v2:
>   * address remarks from Philipp and Ezequiel
>   - update commit message
>   - rename offset to bytes_per_mb
>   - remove MV_OFFSET macros
>   - move PIC_MB_WIDTH/HEIGHT_P change to separate patch
> ---
>  .../staging/media/hantro/hantro_g1_h264_dec.c | 29 +++++++++++++------
>  1 file changed, 20 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/staging/media/hantro/hantro_g1_h264_dec.c b/drivers/staging/media/hantro/hantro_g1_h264_dec.c
> index 70a6b5b26477..71bf162eaf73 100644
> --- a/drivers/staging/media/hantro/hantro_g1_h264_dec.c
> +++ b/drivers/staging/media/hantro/hantro_g1_h264_dec.c
> @@ -81,7 +81,7 @@ static void set_params(struct hantro_ctx *ctx)
>  		reg |= G1_REG_DEC_CTRL4_CABAC_E;
>  	if (sps->flags & V4L2_H264_SPS_FLAG_DIRECT_8X8_INFERENCE)
>  		reg |= G1_REG_DEC_CTRL4_DIR_8X8_INFER_E;
> -	if (sps->chroma_format_idc == 0)
> +	if (sps->profile_idc >= 100 && sps->chroma_format_idc == 0)
>  		reg |= G1_REG_DEC_CTRL4_BLACKWHITE_E;
>  	if (pps->flags & V4L2_H264_PPS_FLAG_WEIGHTED_PRED)
>  		reg |= G1_REG_DEC_CTRL4_WEIGHT_PRED_E;
> @@ -234,6 +234,7 @@ static void set_buffers(struct hantro_ctx *ctx)
>  	struct vb2_v4l2_buffer *src_buf, *dst_buf;
>  	struct hantro_dev *vpu = ctx->dev;
>  	dma_addr_t src_dma, dst_dma;
> +	size_t offset = 0;
>  
>  	src_buf = hantro_get_src_buf(ctx);
>  	dst_buf = hantro_get_dst_buf(ctx);
> @@ -244,18 +245,28 @@ static void set_buffers(struct hantro_ctx *ctx)
>  
>  	/* Destination (decoded frame) buffer. */
>  	dst_dma = vb2_dma_contig_plane_dma_addr(&dst_buf->vb2_buf, 0);
> -	vdpu_write_relaxed(vpu, dst_dma, G1_REG_ADDR_DST);
> +	/* Adjust dma addr to start at second line for bottom field */
> +	if (ctrls->slices[0].flags & V4L2_H264_SLICE_FLAG_BOTTOM_FIELD)
> +		offset = ALIGN(ctx->dst_fmt.width, MB_DIM);
> +	vdpu_write_relaxed(vpu, dst_dma + offset, G1_REG_ADDR_DST);
>  
>  	/* Higher profiles require DMV buffer appended to reference frames. */
>  	if (ctrls->sps->profile_idc > 66 && ctrls->decode->nal_ref_idc) {
> -		size_t pic_size = ctx->h264_dec.pic_size;
> -		size_t mv_offset = round_up(pic_size, 8);
> -
> +		unsigned int bytes_per_mb = 384;

Nitpick: can you add a blank line here?

> +		/* DMV buffer for monochrome start directly after Y-plane */
> +		if (ctrls->sps->profile_idc >= 100 &&
> +		    ctrls->sps->chroma_format_idc == 0)
> +			bytes_per_mb = 256;
> +		offset = bytes_per_mb * MB_WIDTH(ctx->dst_fmt.width) *
> +			 MB_HEIGHT(ctx->dst_fmt.height);
> +
> +		/* DMV buffer is split in two for field encoded frames,

Nitpick again: can you use non-net-style comments.

		/*
		 * Blabla
		 */

> +		 * adjust offset for bottom field
> +		 */
>  		if (ctrls->slices[0].flags & V4L2_H264_SLICE_FLAG_BOTTOM_FIELD)
> -			mv_offset += 32 * MB_WIDTH(ctx->dst_fmt.width);
> -
> -		vdpu_write_relaxed(vpu, dst_dma + mv_offset,
> -				   G1_REG_ADDR_DIR_MV);
> +			offset += 32 * MB_WIDTH(ctx->dst_fmt.width) *
> +				  MB_HEIGHT(ctx->dst_fmt.height);
> +		vdpu_write_relaxed(vpu, dst_dma + offset, G1_REG_ADDR_DIR_MV);
>  	}
>  
>  	/* Auxiliary buffer prepared in hantro_g1_h264_dec_prepare_table(). */