[Intel-gfx] [PATCH 3/7] drm/i915/skl: Adjust intel_fb_align_height() for Yb/Yf tiling

[Damien Lespiau]

On Wed, Feb 25, 2015 at 10:54:31AM +0000, Tvrtko Ursulin wrote:
> 
> On 02/24/2015 04:54 PM, Damien Lespiau wrote:
> >On Mon, Feb 23, 2015 at 03:55:57PM +0000, Tvrtko Ursulin wrote:
> >>From: Damien Lespiau <damien.lespiau at intel.com>
> >>
> >>We now need the bpp of the fb as Yf tiling has different tile widths
> >>depending on it.
> >>
> >>v2: Rebased for the new addfb2 interface. (Tvrtko Ursulin)
> >>v3: Rebased for fb modifier changes. (Tvrtko Ursulin)
> >>
> >>Signed-off-by: Damien Lespiau <damien.lespiau at intel.com>
> >>Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> >>Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> >
> >Might want to add a MISSING_CASE() here as well. For the record, the
> 
> Will do.
> 
> >vertical alignments for Yf are taken from a dodgy looking document found
> >by chance.
> >
> >We don't have a 128bpp format supported by display
> 
> Ok but we can't really error out from this helper so what do you suggest?

We could just remove the 128 case, we can't reach it.

> >Now that I think about it, for the horizontal stride, BSpec says:
> >
> >   - 8 bpp -> 64 bytes
> >   - * bpp -> 128 bytes
> >
> >Given that a tile is a page size this would give for the vertical
> >alignment:
> >
> >   - 8 bpp -> 64 byes (that's what we have)
> >   - * -> 32 bytes
> >
> >So the 64bpp cases look a bit suspicious. Given that one the goals for
> >this new tiling format is to have tiles as square as possible (in terms
> >of pixels, not byte size), it'd make sense to have different strides
> >constraints for the 64bpp format, so it could be BSpec being wrong on
> >the horizontal stride constraint for 64bpp?
> 
> It's either square or 2:1 rectangular. I'll try to double check the numbers
> for 64bpp then.

Thanks. Thinking about it a bit more, it could just be that the display
engine has a slightly stricter constraint than the 3D pipeline for the
alignment of 64bpc fbs. And so the code would be fine. It's all
assumptions though.

-- 
Damien