linux-kernel - [PATCH 2/2] media: cedrus: Fix H264 decoding

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Date:   Wed, 23 Dec 2020 12:06:59 +0100
From:   Jernej Skrabec <jernej.skrabec@...l.net>
To:     mripard@...nel.org, paul.kocialkowski@...tlin.com
Cc:     mchehab@...nel.org, wens@...e.org, jernej.skrabec@...l.net,
        hans.verkuil@...co.com, nicolas.dufresne@...labora.com,
        linux-media@...r.kernel.org, devel@...verdev.osuosl.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        gregkh@...uxfoundation.org, linux-sunxi@...glegroups.com,
        Andre Heider <a.heider@...il.com>
Subject: [PATCH 2/2] media: cedrus: Fix H264 decoding

During H264 API overhaul subtle bug was introduced Cedrus driver.
Progressive references have both, top and bottom reference flags set.
Cedrus reference list expects only bottom reference flag and only when
interlaced frames are decoded. However, due to a bug in Cedrus check,
exclusivity is not tested and that flag is set also for progressive
references. That causes "jumpy" background with many videos.

Fix that by checking that only bottom reference flag is set in control
and nothing else.

Tested-by: Andre Heider <a.heider@...il.com>
Fixes: cfc8c3ed533e ("media: cedrus: h264: Properly configure reference field")
Signed-off-by: Jernej Skrabec <jernej.skrabec@...l.net>
---
 drivers/staging/media/sunxi/cedrus/cedrus_h264.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_h264.c b/drivers/staging/media/sunxi/cedrus/cedrus_h264.c
index 781c84a9b1b7..de7442d4834d 100644
--- a/drivers/staging/media/sunxi/cedrus/cedrus_h264.c
+++ b/drivers/staging/media/sunxi/cedrus/cedrus_h264.c
@@ -203,7 +203,7 @@ static void _cedrus_write_ref_list(struct cedrus_ctx *ctx,
 		position = cedrus_buf->codec.h264.position;
 
 		sram_array[i] |= position << 1;
-		if (ref_list[i].fields & V4L2_H264_BOTTOM_FIELD_REF)
+		if (ref_list[i].fields == V4L2_H264_BOTTOM_FIELD_REF)
 			sram_array[i] |= BIT(0);
 	}
 
-- 
2.29.2