Re: [PATCH v2] drm/i915: correct the pitch check for NV12 framebuffer

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Dec 12, 2018 at 09:33:49PM +0100, Daniel Vetter wrote:
> On Wed, Dec 12, 2018 at 9:24 PM Ville Syrjälä
> <ville.syrjala@linux.intel.com> wrote:
> >
> > On Tue, Dec 11, 2018 at 04:39:05PM -0800, Dongseong Hwang wrote:
> > > framebuffer for NV12 requires the pitch to the multiplier of 4, instead
> > > of the width. This patch corrects it.
> > >
> > > For instance, a 480p video, whose width and pitch are 854 and 896
> > > respectively, is excluded for NV12 plane so far.
> > >
> > > Signed-off-by: Dongseong Hwang <dongseong.hwang@intel.com>
> > > Cc: Chandra Konduru <chandra.konduru@intel.com>
> > > Cc: Vidya Srinivas <vidya.srinivas@intel.com>
> > > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > Cc: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
> > > ---
> > >  drivers/gpu/drm/i915/intel_display.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > > index 13e5650..8a3de12 100644
> > > --- a/drivers/gpu/drm/i915/intel_display.c
> > > +++ b/drivers/gpu/drm/i915/intel_display.c
> > > @@ -14600,7 +14600,7 @@ static int intel_framebuffer_init(struct intel_framebuffer *intel_fb,
> > >       if (fb->format->format == DRM_FORMAT_NV12 &&
> > >           (fb->width < SKL_MIN_YUV_420_SRC_W ||
> > >            fb->height < SKL_MIN_YUV_420_SRC_H ||
> > > -          (fb->width % 4) != 0 || (fb->height % 4) != 0)) {
> > > +          (fb->pitches[0] % 4) != 0 || (fb->height % 4) != 0)) {
> >
> > The stride can never be misaligned like that. It'll be at least tile
> > aligned, or 64 byte aligned with linear buffers.
> >
> > Anyways this entire piece of code doesn't make too much sense. The fb
> > size doesn't really matter for us, only the src viewport size matters.
> > That one we limit to a minimum of 2x2 pixels w/o scaling, and 16x16
> > pixems w/ scaling. So looks like this code can be just ripped out.
> 
> Do we have igt testcases for these cornercases in igt? Obviously would
> need to be intel specific subtests ...

Can't spot anything quite that specific. Someone would need to write
one I suppose. Also Imre has a test somewhere on the list for testing
the plane clipping underrun fails which tests small src viewport sizes,
and JP has been working on a rotation vs. clipping test that is also
somewhat related. Not sure if we could combine any of these somehow
to avoid having too many similar tests.

-- 
Ville Syrjälä
Intel
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