[Intel-gfx] [PATCH 1/2] drm/i915/mtl: Added restriction for plane downscaling

[Luca Coelho]

On Mon, 2022-08-29 at 02:48 +0000, Murthy, Arun R wrote:
> > -----Original Message-----
> > From: Intel-gfx <intel-gfx-bounces at lists.freedesktop.org> On Behalf
> > Of
> > Animesh Manna
> > Sent: Friday, August 26, 2022 5:48 PM
> > To: intel-gfx at lists.freedesktop.org
> > Subject: [Intel-gfx] [PATCH 1/2] drm/i915/mtl: Added restriction
> > for plane
> > downscaling
> > 
> > The second Scaler (i.e. Scaler 2) does not support vertical
> > downscaling (i.e.
> > it's vertical scale factor must not be greater than 1.0). So,
> > vertical plane
> > downscaling is not supported on MTL, scale factor modified
> > accordingly.
> > 
> > Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > Cc: Manasi Navare <manasi.d.navare at intel.com>
> > Signed-off-by: Animesh Manna <animesh.manna at intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/skl_universal_plane.c | 7 +++++--
> >  1 file changed, 5 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/skl_universal_plane.c
> > b/drivers/gpu/drm/i915/display/skl_universal_plane.c
> > index bcfde81e4d08..6bfcda748e7b 100644
> > --- a/drivers/gpu/drm/i915/display/skl_universal_plane.c
> > +++ b/drivers/gpu/drm/i915/display/skl_universal_plane.c
> > @@ -1464,9 +1464,12 @@ static int skl_plane_max_scale(struct
> > drm_i915_private *dev_priv,
> >  	 * whether we can use the HQ scaler mode. Assume
> >  	 * the best case.
> >  	 * FIXME need to properly check this later.
> > +	 * FIXME On MTL, adjust specific scaler's downscaling
> > capability.
> This should not be FIXME and this is a limitation of hardware. A NOTE
> can be added instead!

I have been working on this and I have a proper implementation for this
FIXME.

This patch is not correct because it limits scaling on all cases, i.e.
vertical scaling, horizontal scaling and both in scaler 1 and scaler 2.
But the hardware limitation is only in vertical scaling with scaler 2.

I sent the fix to our internal list last Friday.  I think we should
only take this patch upstream after it has been squashed with my
changes.


> >  	 */
> > -	if (DISPLAY_VER(dev_priv) >= 10 ||
> > -	    !intel_format_info_is_yuv_semiplanar(fb->format, fb-
> > >modifier))
> > +	if (IS_METEORLAKE(dev_priv))
> > +		return 0x10000;
> Can this magic number be replaced with a macro?

This is not really a magic number, it's a 16.16 fixed point notation. 
0x10000 represents 1.0 (no scaling).


--
Cheers,
Luca.