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

[Jammy Huang]

On 2022/1/24 下午 06:22, Hans Verkuil wrote:
> 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.
OK, I will combine 3/4 into a single patch in next series.
Thanks.

Best Regards,

        Jammy
> 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;