Re: [PATCH] drm/ingenic: ipu: Search for scaling coefs up to 102% of?? the screen

[Paul Cercueil]

Le mar. 10 nov. 2020 à 9:56, Sam Ravnborg <sam@xxxxxxxxxxxx> a écrit :
> Hi Paul,
> On Tue, Nov 10, 2020 at 08:50:22AM +0000, Paul Cercueil wrote:
> >  Hi,
> >
> >  Le sam. 7 nov. 2020 à 20:33, Sam Ravnborg <sam@xxxxxxxxxxxx> a 
> > écrit :
> >  > Hi Paul.
> >  >
> >  > On Thu, Nov 05, 2020 at 08:39:05AM +0000, Paul Cercueil wrote:
> >  > >  Increase the scaled image's theorical width/height until we 
> > find a
> >  > >  configuration that has valid scaling coefficients, up to 102% 
> > of the
> >  > >  screen's resolution. This makes sure that we can scale from 
> > almost
> >  > >  every resolution possible at the cost of a very small 
> > distorsion.
> >  > >  The CRTC_W / CRTC_H are not modified.
> >  > >
> >  > >  This algorithm was already in place but would not try to go 
> > above
> >  > > the
> >  > >  screen's resolution, and as a result would only work if the 
> > CRTC_W /
> >  > >  CRTC_H were smaller than the screen resolution. It will now try
> >  > > until it
> >  > >  reaches 102% of the screen's resolution.
> >  > >
> >  > >  Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
> >  >
> >  > Looks like the patch does what the descriptions says.
> >  > So in other words - look OK to me. I am not confident enogh for a 
> > r-b
> >  > but my code reading is enough to warrant an a-b:
> >  > Acked-by: Sam Ravnborg <sam@xxxxxxxxxxxx>
> >
> >  Note that this algorithm exists mostly as a band-aid for a missing
> >  functionality: it is not possible for userspace to request the 
> > closest mode
> >  that would encapsulate the provided one, because the GEM buffer is 
> > created
> >  beforehand. If there was a way to let the kernel tweak the mode, I 
> > could
> >  write a better algorithm that would result in a better looking 
> > picture.
>
> Could you add this nice explanation to the changelog so when we wonder
> why this was done in some years we can dig up this from git history.

Sure!

-Paul