On 2022/1/21 下午 03:30, Hans Verkuil wrote:
On 12/22/21 09:21, Jammy Huang wrote:
This is a workaround for sync polarity unstable.
Sync value get by VR09C counts from sync's rising edge, which means
sync's polarity is negative if sync value is bigger than total/2.
Do you have an example of such a format, or is this mostly theoretical?
Either provide the example or make a note that it is theoretical.
OK, I will update an example in next patch. Let me explain first.
This is a must-be result. Please refer to the graph below as I sent in
3/4 of this
series. For negative sync, sync width equals to back porch + data enable
+ front porch.
Thus, sync would be bigger than 90% of total in most cases.
+-------------------+
| v i d e o |
+--+ +-----+ +-----+ +---+
| | | |
+--+ +--+
vsync+-------------------------------+
frame_top+-----+
frame_bottom+-------------------------+
Following registers are what I got for 1920x1200@60.
1e700090: 07ee206f 04c9001a c4d3efff 04cc001f
1e7000a0: 0000081f 00000000 00000000 00000000
vertical total = 0x4D3 (VR098[27:16]) = 1235
vertical sync = 0x4CC (VR09C[27:16]) = 1228
Regards,
Hans
Signed-off-by: Jammy Huang <jammy_huang@xxxxxxxxxxxxxx>
---
v2:
- Use 'total/2' rather than 'total<<1'
- Update comment
---
drivers/media/platform/aspeed-video.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/drivers/media/platform/aspeed-video.c b/drivers/media/platform/aspeed-video.c
index 7c50567f5ab0..c3e3343d91e1 100644
--- a/drivers/media/platform/aspeed-video.c
+++ b/drivers/media/platform/aspeed-video.c
@@ -989,6 +989,16 @@ static void aspeed_video_get_resolution(struct aspeed_video *video)
video->frame_bottom = FIELD_GET(VE_SRC_TB_EDGE_DET_BOT, src_tb_edge);
video->frame_top = FIELD_GET(VE_SRC_TB_EDGE_DET_TOP, src_tb_edge);
+
+ /*
+ * This is a workaround for polarity detection when the sync
+ * value is larger than half.
+ */
+ if (vsync > (vtotal / 2))
+ det->polarities &= ~V4L2_DV_VSYNC_POS_POL;
+ else
+ det->polarities |= V4L2_DV_VSYNC_POS_POL;
+
if (det->polarities & V4L2_DV_VSYNC_POS_POL) {
det->vbackporch = video->frame_top - vsync;
det->vfrontporch = vtotal - video->frame_bottom;
@@ -1003,6 +1013,16 @@ static void aspeed_video_get_resolution(struct aspeed_video *video)
video->frame_right = FIELD_GET(VE_SRC_LR_EDGE_DET_RT, src_lr_edge);
video->frame_left = FIELD_GET(VE_SRC_LR_EDGE_DET_LEFT, src_lr_edge);
+
+ /*
+ * This is a workaround for polarity detection when the sync
+ * value is larger than half.
+ */
+ if (hsync > (htotal / 2))
+ det->polarities &= ~V4L2_DV_HSYNC_POS_POL;
+ else
+ det->polarities |= V4L2_DV_HSYNC_POS_POL;
+
if (det->polarities & V4L2_DV_HSYNC_POS_POL) {
det->hbackporch = video->frame_left - hsync;
det->hfrontporch = htotal - video->frame_right;
--
Best Regards
Jammy
