Re: [PATCH 2/2] media: verisilicon: add WebP decoding support

[Nicolas Dufresne]

Hi Hugues,

Le mercredi 11 septembre 2024 à 15:50 +0200, Hugues Fruchet a écrit :
> Add WebP picture decoding support to VP8 stateless decoder.

Unless when its obvious, the commit message should explain what is being
changed.

> 
> Signed-off-by: Hugues Fruchet <hugues.fruchet@xxxxxxxxxxx>
> ---
>  drivers/media/platform/verisilicon/hantro_g1_regs.h    | 1 +
>  drivers/media/platform/verisilicon/hantro_g1_vp8_dec.c | 7 +++++++
>  2 files changed, 8 insertions(+)
> 
> diff --git a/drivers/media/platform/verisilicon/hantro_g1_regs.h b/drivers/media/platform/verisilicon/hantro_g1_regs.h
> index c623b3b0be18..e7d4db788e57 100644
> --- a/drivers/media/platform/verisilicon/hantro_g1_regs.h
> +++ b/drivers/media/platform/verisilicon/hantro_g1_regs.h
> @@ -232,6 +232,7 @@
>  #define     G1_REG_DEC_CTRL7_DCT7_START_BIT(x)		(((x) & 0x3f) << 0)
>  #define G1_REG_ADDR_STR					0x030
>  #define G1_REG_ADDR_DST					0x034
> +#define G1_REG_ADDR_DST_CHROMA				0x038
>  #define G1_REG_ADDR_REF(i)				(0x038 + ((i) * 0x4))
>  #define     G1_REG_ADDR_REF_FIELD_E			BIT(1)
>  #define     G1_REG_ADDR_REF_TOPC_E			BIT(0)
> diff --git a/drivers/media/platform/verisilicon/hantro_g1_vp8_dec.c b/drivers/media/platform/verisilicon/hantro_g1_vp8_dec.c
> index 851eb67f19f5..c6a7584b716a 100644
> --- a/drivers/media/platform/verisilicon/hantro_g1_vp8_dec.c
> +++ b/drivers/media/platform/verisilicon/hantro_g1_vp8_dec.c
> @@ -427,6 +427,11 @@ static void cfg_buffers(struct hantro_ctx *ctx,
>  
>  	dst_dma = hantro_get_dec_buf_addr(ctx, &vb2_dst->vb2_buf);
>  	vdpu_write_relaxed(vpu, dst_dma, G1_REG_ADDR_DST);
> +
> +	if (hdr->flags & V4L2_VP8_FRAME_FLAG_WEBP)
> +		vdpu_write_relaxed(vpu, dst_dma +
> +				   ctx->dst_fmt.height * ctx->dst_fmt.width,

I'm not really not fan of that type of formula using padded width/height. Not
sure if its supported already, but if we have foreign buffers with a bigger
bytesperline, the IP may endup overwriting the luma. Please use the per-plane
bytesperline, we have v4l2-common to help with that when needed.
> +				   G1_REG_ADDR_DST_CHROMA);

I have a strong impression this patch is incomplete (not generic enough). The
documentation I have indicates that the resolution range for WebP can be
different for different synthesis. See swreg54 (0xd8), if bit 19 is set, then it
can support 16K x 16K resolution. There is no other way around that then
signalling explicitly at the format level that this is webp, since otherwise you
can't know from userspace and can't enumerate the different resolution. I'm
curious what is the difference at bitstream level, would be nice to clarify too.

On GStreamer side, the formats are entirely seperate, image/webp vs video/x-vp8
are the mime types. Seems a lot safe to keep these two as seperate formats. They
can certainly share the same stateless frame structure, with the additional flag
imho.

Nicolas

>  }
>  
>  int hantro_g1_vp8_dec_run(struct hantro_ctx *ctx)
> @@ -471,6 +476,8 @@ int hantro_g1_vp8_dec_run(struct hantro_ctx *ctx)
>  		reg |= G1_REG_DEC_CTRL0_SKIP_MODE;
>  	if (hdr->lf.level == 0)
>  		reg |= G1_REG_DEC_CTRL0_FILTERING_DIS;
> +	if (hdr->flags & V4L2_VP8_FRAME_FLAG_WEBP)
> +		reg |= G1_REG_DEC_CTRL0_WEBP_E;
>  	vdpu_write_relaxed(vpu, reg, G1_REG_DEC_CTRL0);
>  
>  	/* Frame dimensions */