Re: [PATCH v2 4/4] media: aspeed: Fix timing polarity incorrect

Jammy Huang
2022-01-24T02:30:52Z

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