Messages in this thread Patch in this message | | | Date | Mon, 24 Jan 2022 10:29:46 +0800 | Subject | Re: [PATCH v2 4/4] media: aspeed: Fix timing polarity incorrect | From | Jammy Huang <> |
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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@aspeedtech.com> >> --- >> 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
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