On 24/01/2022 03:29, Jammy Huang wrote:
>
> 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.
Right, I suspected that might be the case.
I think it would be better to combine patches 3 and 4 into a single
patch, since they are closely related and it is actually easier to
understand if it's just a single patch.
Regards,
Hans
>
> +-------------------+
> | 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;
>
