[igt-dev] [PATCH i-g-t 2/4] lib/igt_fb/tgl+: Prevent CCS FB UV surface offset overalignment

[Imre Deak]

On Wed, Oct 27, 2021 at 12:46:11PM +0300, Ville Syrjälä wrote:
> On Wed, Oct 27, 2021 at 12:26:18AM +0300, Imre Deak wrote:
> > The offset of semiplanar UV surfaces in CCS FBs must be 64 kbyte aligned
> > as required by the Vebox engine which IGT uses to convert between tiling
> > formats. At the same time the display engine requires the offset to be
> > tile-row aligned. So far we ensured both of these alignment requirements
> > by aligning all color surface widths/heights to 4x4 tiles. This however
> > wastes memory in case the number of tiles in one tile-row modulo 16 is 0
> > or 8 where 1 or 2 tile-row alignment correspondingly would be enough.
> > 
> > The next patch removes the 4x4 tile alignment, here prepare for that by
> > aligning TGL+ UV surface offsets to LCM(tile-row size, 64 kbyte)
> > ensuring the minimum tile-row size and 64 kbyte alignment.
> > 
> > Signed-off-by: Imre Deak <imre.deak at intel.com>
> > ---
> >  lib/igt_fb.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 51 insertions(+)
> > 
> > diff --git a/lib/igt_fb.c b/lib/igt_fb.c
> > index b8b2396d3..86d0ae426 100644
> > --- a/lib/igt_fb.c
> > +++ b/lib/igt_fb.c
> > @@ -392,6 +392,12 @@ bool igt_format_is_yuv_semiplanar(uint32_t format)
> >  	return igt_format_is_yuv(format) && f->num_planes == 2;
> >  }
> >  
> > +static bool is_yuv_semiplanar_plane(const struct igt_fb *fb, int color_plane)
> > +{
> > +	return igt_format_is_yuv_semiplanar(fb->drm_format) &&
> > +	       color_plane == 1;
> > +}
> > +
> >  /**
> >   * igt_get_fb_tile_size:
> >   * @fd: the DRM file descriptor
> > @@ -843,16 +849,61 @@ static uint64_t calc_plane_size(struct igt_fb *fb, int plane)
> >  	}
> >  }
> >  
> > +static unsigned int gcd(unsigned int a, unsigned int b)
> > +{
> > +	if (b == 0)
> > +		return a;
> > +
> > +	return gcd(b, a % b);
> 
> I would write that w/o the recursion. 

Ok, will change it.

> -- 
> Ville Syrjälä
> Intel