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

Hans Verkuil
2022-01-21T07:30:25Z

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.

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;