media: coda: fix mpeg2 sequence number handling

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>

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

@@ -1746,6 +1746,7 @@ static int __coda_start_decoding(struct coda_ctx *ctx)
 		v4l2_err(&dev->v4l2_dev, "CODA_COMMAND_SEQ_INIT timeout\n");
 		return ret;
 	}
+	ctx->sequence_offset = ~0U;
 	ctx->initialized = 1;
 
 	/* Update kfifo out pointer from coda bitstream read pointer */
@@ -2169,7 +2170,9 @@ 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(&ctx->buffer_meta_lock);
 		if (!list_empty(&ctx->buffer_meta_list)) {