Re: [PATCH] media: verisilicon: postproc: fix the G1 input height extension

[Nicolas Dufresne <nicolas.dufresne@collabora.com>]

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Le mercredi 04 novembre 2026 à 14:27 +0300, Sergei Khomenkov via B4 Relay a
écrit :
> From: Sergei Khomenkov <shomenkow@gmail.com>
> 
> The G1 post-processor takes its input size in macroblocks: the low
> bits in swreg72, the high bits in swreg92 (bits 28:26 for bits 11:9
> of the width, bits 31:29 for bits 10:8 of the height). This is the
> VDPU1 layout in Rockchip's MPP library, whose JPEG decoder writes the
> height extension as ((height / 16) & 0x700) >> 8.
> 
> hantro_postproc_g1_enable() computes the width extension that way but
> writes the height extension as MB_HEIGHT(height >> 8), shifting lines
> instead of macroblocks. Every input of 256 to 4080 lines gets an
> extension of 1 instead of 0, so the post-processor is told it has 256
> more macroblock rows than it has: 286 instead of 30 for 480 lines,
> 301 instead of 45 for 720 and 324 instead of 68 for 1080. Inputs
> below 256 lines are not affected.
> 
> Shift the macroblock count, as is done for the width.
> 
> The problem was found with an LLM coding assistant while porting
> mainline Linux to a Rockchip RK3026 board; the assistant also drafted
> this change. Tested on that board (G1, ID 0x6731), decoding H.264
> (640x480, 854x480, 1280x720) and VP8 (640x480, 1280x720) to YUYV
> through the post-processor, 241 frames, against a software conversion
> of the decoder's NV12 output. Without this change only the 4 VP8 key
> frames match: a few pixels at the bottom left of the last macroblock
> row differ from run to run, and VP8 inter frames propagate them. With
> it all 241 frames match. 320x240 is correct either way.
> 
> Fixes: 3f6702e1be8a ("media: verisilicon: postproc: 4K support")
> Cc: stable@vger.kernel.org
> Signed-off-by: Sergei Khomenkov <shomenkow@gmail.com>
> ---
>  drivers/media/platform/verisilicon/hantro_postproc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/media/platform/verisilicon/hantro_postproc.c b/drivers/media/platform/verisilicon/hantro_postproc.c
> index e94d1ba5ef10..ecc6b3137eb0 100644
> --- a/drivers/media/platform/verisilicon/hantro_postproc.c
> +++ b/drivers/media/platform/verisilicon/hantro_postproc.c
> @@ -106,7 +106,7 @@ static void hantro_postproc_g1_enable(struct hantro_ctx *ctx)
>  	HANTRO_PP_REG_WRITE(vpu, orig_width, MB_WIDTH(ctx->dst_fmt.width));
>  	HANTRO_PP_REG_WRITE(vpu, display_width, ctx->dst_fmt.width);
>  	HANTRO_PP_REG_WRITE(vpu, input_width_ext, MB_WIDTH(ctx->dst_fmt.width) >> 9);
> -	HANTRO_PP_REG_WRITE(vpu, input_height_ext, MB_HEIGHT(ctx->dst_fmt.height >> 8));
> +	HANTRO_PP_REG_WRITE(vpu, input_height_ext, MB_HEIGHT(ctx->dst_fmt.height) >> 8);

Good catch.

Reviewed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>

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