media: cedrus: Allow using the current dst buffer as reference

It was reported that some cases of interleaved video decoding require
using the current destination buffer as a reference. However, this is
no longer possible after the move to vb2_find_timestamp because only
dequeued and done buffers are considered.

Add a helper in our driver that also considers the current destination
buffer before resorting to vb2_find_timestamp and use it in MPEG-2.
Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/staging/media/sunxi/cedrus/cedrus_dec.c

@@ -22,6 +22,19 @@
 #include "cedrus_dec.h"
 #include "cedrus_hw.h"
 
+int cedrus_reference_index_find(struct vb2_queue *queue,
+				struct vb2_buffer *vb2_buf, u64 timestamp)
+{
+	/*
+	 * Allow using the current capture buffer as reference, which can occur
+	 * for field-coded pictures.
+	 */
+	if (vb2_buf->timestamp == timestamp)
+		return vb2_buf->index;
+	else
+		return vb2_find_timestamp(queue, timestamp, 0);
+}
+
 void cedrus_device_run(void *priv)
 {
 	struct cedrus_ctx *ctx = priv;

drivers/staging/media/sunxi/cedrus/cedrus_dec.h

@@ -16,6 +16,8 @@
 #ifndef _CEDRUS_DEC_H_
 #define _CEDRUS_DEC_H_
 
+int cedrus_reference_index_find(struct vb2_queue *queue,
+				struct vb2_buffer *vb2_buf, u64 timestamp);
 void cedrus_device_run(void *priv);
 
 #endif

drivers/staging/media/sunxi/cedrus/cedrus_mpeg2.c

@@ -10,6 +10,7 @@
 #include <media/videobuf2-dma-contig.h>
 
 #include "cedrus.h"
+#include "cedrus_dec.h"
 #include "cedrus_hw.h"
 #include "cedrus_regs.h"
 
@@ -159,8 +160,8 @@ static void cedrus_mpeg2_setup(struct cedrus_ctx *ctx, struct cedrus_run *run)
 	cedrus_write(dev, VE_DEC_MPEG_PICBOUNDSIZE, reg);
 
 	/* Forward and backward prediction reference buffers. */
-	forward_idx = vb2_find_timestamp(cap_q,
-					 slice_params->forward_ref_ts, 0);
+	forward_idx = cedrus_reference_index_find(cap_q, &run->dst->vb2_buf,
+						  slice_params->forward_ref_ts);
 
 	fwd_luma_addr = cedrus_dst_buf_addr(ctx, forward_idx, 0);
 	fwd_chroma_addr = cedrus_dst_buf_addr(ctx, forward_idx, 1);
@@ -168,8 +169,9 @@ static void cedrus_mpeg2_setup(struct cedrus_ctx *ctx, struct cedrus_run *run)
 	cedrus_write(dev, VE_DEC_MPEG_FWD_REF_LUMA_ADDR, fwd_luma_addr);
 	cedrus_write(dev, VE_DEC_MPEG_FWD_REF_CHROMA_ADDR, fwd_chroma_addr);
 
-	backward_idx = vb2_find_timestamp(cap_q,
-					  slice_params->backward_ref_ts, 0);
+	backward_idx = cedrus_reference_index_find(cap_q, &run->dst->vb2_buf,
+						   slice_params->backward_ref_ts);
+
 	bwd_luma_addr = cedrus_dst_buf_addr(ctx, backward_idx, 0);
 	bwd_chroma_addr = cedrus_dst_buf_addr(ctx, backward_idx, 1);