media: coda: fix mpeg2 sequence number handling

BugLink: https://bugs.launchpad.net/bugs/1840081

[ Upstream commit 56d159a4 ]

Sequence number handling assumed that the BIT processor frame number
starts counting at 1, but this is not true for the MPEG-2 decoder,
which starts at 0. Fix the sequence counter offset detection to handle
this.
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/media/platform/coda/coda-bit.c

@@ -1581,6 +1581,7 @@ static int __coda_start_decoding(struct coda_ctx *ctx)
 		coda_write(dev, 0, CODA_REG_BIT_BIT_STREAM_PARAM);
 		return -ETIMEDOUT;
 	}
+	ctx->sequence_offset = ~0U;
 	ctx->initialized = 1;
 
 	/* Update kfifo out pointer from coda bitstream read pointer */
@@ -1971,7 +1972,9 @@ static void coda_finish_decode(struct coda_ctx *ctx)
 		v4l2_err(&dev->v4l2_dev,
 			 "decoded frame index out of range: %d\n", decoded_idx);
 	} else {
-		val = coda_read(dev, CODA_RET_DEC_PIC_FRAME_NUM) - 1;
+		val = coda_read(dev, CODA_RET_DEC_PIC_FRAME_NUM);
+		if (ctx->sequence_offset == -1)
+			ctx->sequence_offset = val;
 		val -= ctx->sequence_offset;
 		spin_lock_irqsave(&ctx->buffer_meta_lock, flags);
 		if (!list_empty(&ctx->buffer_meta_list)) {