[PATCH v2] media: coda: Fix H.264 header alignment.

[javier.martin@vista-silicon.com]

From: Javier Martin <javier.martin@vista-silicon.com>

Length of H.264 headers is variable and thus it might not be
aligned for the coda to append the encoded frame. This causes
the first frame to overwrite part of the H.264 PPS.

In order to solve that, a filler NAL must be added between
the headers and the first frame to preserve alignment.

Signed-off-by: Javier Martin <javier.martin@vista-silicon.com>
---
Changes since v1:
 - Align to 64bits as requested by Philipp.

---
 drivers/media/platform/coda.c |   30 +++++++++++++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/drivers/media/platform/coda.c b/drivers/media/platform/coda.c
index a8c7a94..7febcd9 100644
--- a/drivers/media/platform/coda.c
+++ b/drivers/media/platform/coda.c
@@ -177,6 +177,10 @@ struct coda_ctx {
 	int				idx;
 };
 
+static const u8 coda_filler_nal[14] = { 0x00, 0x00, 0x00, 0x01, 0x0c, 0xff,
+			0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x80 };
+static const u8 coda_filler_size[8] = { 0, 7, 14, 13, 12, 11, 10, 9 };
+
 static inline void coda_write(struct coda_dev *dev, u32 data, u32 reg)
 {
 	v4l2_dbg(1, coda_debug, &dev->v4l2_dev,
@@ -938,6 +942,24 @@ static int coda_alloc_framebuffers(struct coda_ctx *ctx, struct coda_q_data *q_d
 	return 0;
 }
 
+static int coda_h264_padding(int size, char *p)
+{
+	int nal_size;
+	int diff;
+
+	diff = size - (size & ~0x7);
+	if (diff == 0)
+		return 0;
+
+	nal_size = coda_filler_size[diff];
+	memcpy(p, coda_filler_nal, nal_size);
+
+	/* Add rbsp stop bit and trailing at the end */
+	*(p + nal_size - 1) = 0x80;
+
+	return nal_size;
+}
+
 static int coda_start_streaming(struct vb2_queue *q, unsigned int count)
 {
 	struct coda_ctx *ctx = vb2_get_drv_priv(q);
@@ -1165,7 +1187,13 @@ static int coda_start_streaming(struct vb2_queue *q, unsigned int count)
 				coda_read(dev, CODA_CMD_ENC_HEADER_BB_START);
 		memcpy(&ctx->vpu_header[1][0], vb2_plane_vaddr(buf, 0),
 		       ctx->vpu_header_size[1]);
-		ctx->vpu_header_size[2] = 0;
+		/*
+		 * Length of H.264 headers is variable and thus it might not be
+		 * aligned for the coda to append the encoded frame. In that is
+		 * the case a filler NAL must be added to header 2.
+		 */
+		ctx->vpu_header_size[2] = coda_h264_padding((ctx->vpu_header_size[0] +
+					ctx->vpu_header_size[1]), ctx->vpu_header[2]);
 		break;
 	case V4L2_PIX_FMT_MPEG4:
 		/*
-- 
1.7.9.5