[PATCH] drm/i915/display: Workaround for odd panning for planar yuv

[Kandpal, Suraj]

> -----Original Message-----
> From: Garg, Nemesa <nemesa.garg at intel.com>
> Sent: Tuesday, October 15, 2024 6:52 PM
> To: Kandpal, Suraj <suraj.kandpal at intel.com>; intel-
> gfx at lists.freedesktop.org
> Subject: RE: [PATCH] drm/i915/display: Workaround for odd panning for
> planar yuv
> 
> 
> 
> > -----Original Message-----
> > From: Kandpal, Suraj <suraj.kandpal at intel.com>
> > Sent: Tuesday, October 15, 2024 2:33 PM
> > To: Garg, Nemesa <nemesa.garg at intel.com>;
> > intel-gfx at lists.freedesktop.org
> > Cc: Garg, Nemesa <nemesa.garg at intel.com>
> > Subject: RE: [PATCH] drm/i915/display: Workaround for odd panning for
> > planar yuv
> >
> >
> >
> > > -----Original Message-----
> > > From: Intel-gfx <intel-gfx-bounces at lists.freedesktop.org> On Behalf
> > > Of Nemesa Garg
> > > Sent: Monday, September 30, 2024 4:54 PM
> > > To: intel-gfx at lists.freedesktop.org
> > > Cc: Garg, Nemesa <nemesa.garg at intel.com>
> > > Subject: [PATCH] drm/i915/display: Workaround for odd panning for
> > > planar yuv
> > >
> > > Disable the support for odd x pan for even xsize for NV12 format as
> > > underrun issue is seen.
> > >
> > > WA: 16024459452
> > >
> > > v2: Replace HSD with WA in commit message [Suraj]
> > >     Modified the condition for handling odd panning
> > >
> > > v3: Simplified the condition for checking hsub
> > >     Using older framework for wa as rev1[Jani]
> > >
> > > v4: Modify the condition for hsub [Sai Teja]
> > >     Initialize hsub in else path [Dan]
> > >
> > > v5: Replace IS_LUNARLAKE with display version.
> > >     Resolve nitpicks[Jani]
> > >
> > > Signed-off-by: Nemesa Garg <nemesa.garg at intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/display/intel_atomic_plane.c | 8 ++++++++
> > >  1 file changed, 8 insertions(+)
> > >
> > > diff --git a/drivers/gpu/drm/i915/display/intel_atomic_plane.c
> > > b/drivers/gpu/drm/i915/display/intel_atomic_plane.c
> > > index e979786aa5cf..e3401a4f7992 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_atomic_plane.c
> > > +++ b/drivers/gpu/drm/i915/display/intel_atomic_plane.c
> > > @@ -1029,6 +1029,14 @@ int intel_plane_check_src_coordinates(struct
> > > intel_plane_state *plane_state)
> > >  		 * This allows NV12 and P0xx formats to have odd size
> and/or
> > odd
> > >  		 * source coordinates on DISPLAY_VER(i915) >= 20
> > >  		 */
> > > +		/*
> > > +		 *  Wa_16023981245 for display version 20.
> > > +		 *  Do not support odd x-panning for even xsize for NV12.
> >
> > Only mention WA no here the rest anyone can refer to by going and
> > checking the HSD
> Sure..will do.
> >
> > > +		 */
> > > +		if (DISPLAY_VER(i915) == 20 && fb->format->format ==
> > > DRM_FORMAT_NV12 &&
> > > +		    src_x % 2 != 0 && src_w % 2 == 0)
> > > +			return -EINVAL;
> >
> > Also rather than return -EINVAL here we set hsub =2 and vsub =1 this
> > should make sure odd panning is disabled When we have even size since
> > we only need to disable odd panning according to hsd not even panning
> > this return may end stop panning for even sizes all together.
> >
> Even if I do hsub=2 then also it will return -EINVAL as src_x will be odd and
> src_x % hsub will be 1 which will return -EINVAL.
> Even panning doesn't get disable that's why I have added the check src_x %
> 2 != 0 to make sure that position in not even and src_w % 2 to check for
> even size.


That will be fine let the code later that already exists take care of that since we don't
Want to abruptly send an -EINVAL in a code block where we were assigning variables. 
When it fails later as you said it will with a clean debug message too.
Secondly when you do return -EINVAL for src_x % 2 != 0 it ends up stopping panning in y direction
If the current src_x is odd but panning is being done only in y direction it will return -EINVAL
Hence assigning hsub and vsub here make a lot more sense.
We can remove the src_x check and keep src_w and add src_h check

Regards,
Suraj Kandpal

> 
> Regards,
> Nemesa
> 
> > Regards,
> > Suraj Kandpal
> > > +
> > >  		hsub = 1;
> > >  		vsub = 1;
> > >  	} else {
> > > --
> > > 2.25.1