[media] coda: implement forced key frames

Implement the V4L2_CID_MPEG_VIDEO_FORCE_KEY_FRAME control to force IDR
frames. This is useful to implement VFU (Video Fast Update) on RTP
transmissions.
We already force an IDR frame at the beginning of each GOP to work
around a firmware bug on i.MX27, use the same mechanism to service IDR
requests from userspace.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

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

@@ -1247,12 +1247,18 @@ static int coda_prepare_encode(struct coda_ctx *ctx)
 	dst_buf->sequence = ctx->osequence;
 	ctx->osequence++;
 
+	force_ipicture = ctx->params.force_ipicture;
+	if (force_ipicture)
+		ctx->params.force_ipicture = false;
+	else if ((src_buf->sequence % ctx->params.gop_size) == 0)
+		force_ipicture = 1;
+
 	/*
 	 * Workaround coda firmware BUG that only marks the first
 	 * frame as IDR. This is a problem for some decoders that can't
 	 * recover when a frame is lost.
 	 */
-	if (src_buf->sequence % ctx->params.gop_size) {
+	if (!force_ipicture) {
 		src_buf->flags |= V4L2_BUF_FLAG_PFRAME;
 		src_buf->flags &= ~V4L2_BUF_FLAG_KEYFRAME;
 	} else {
@@ -1291,8 +1297,7 @@ static int coda_prepare_encode(struct coda_ctx *ctx)
 		pic_stream_buffer_size = q_data_dst->sizeimage;
 	}
 
-	if (src_buf->flags & V4L2_BUF_FLAG_KEYFRAME) {
-		force_ipicture = 1;
+	if (force_ipicture) {
 		switch (dst_fourcc) {
 		case V4L2_PIX_FMT_H264:
 			quant_param = ctx->params.h264_intra_qp;
@@ -1309,7 +1314,6 @@ static int coda_prepare_encode(struct coda_ctx *ctx)
 			break;
 		}
 	} else {
-		force_ipicture = 0;
 		switch (dst_fourcc) {
 		case V4L2_PIX_FMT_H264:
 			quant_param = ctx->params.h264_inter_qp;

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

@@ -1700,6 +1700,9 @@ static int coda_s_ctrl(struct v4l2_ctrl *ctrl)
 	case V4L2_CID_MPEG_VIDEO_CYCLIC_INTRA_REFRESH_MB:
 		ctx->params.intra_refresh = ctrl->val;
 		break;
+	case V4L2_CID_MPEG_VIDEO_FORCE_KEY_FRAME:
+		ctx->params.force_ipicture = true;
+		break;
 	case V4L2_CID_JPEG_COMPRESSION_QUALITY:
 		coda_set_jpeg_compression_quality(ctx, ctrl->val);
 		break;

drivers/media/platform/coda/coda.h

@@ -135,6 +135,7 @@ struct coda_params {
 	u32			vbv_size;
 	u32			slice_max_bits;
 	u32			slice_max_mb;
+	bool			force_ipicture;
 };
 
 struct coda_buffer_meta {