[PATCH] drm/sun4i: Use vi plane as primary

[Roman Stratiienko]

@Jernej Škrabec @Maxime Ripard

Thanks for your time and valuable suggestions.

Currently I would have to go away from mainline KMS to solve my
(Android) issues, and I hope to get back when I
find mainline-friendly solution for it.

Having no primary layer or zero-buffer primary layer and 4 overlays
could be a universal solution, but  I have not sufficient knowledge in
KMS to bring-up this idea.

On Fri, Sep 20, 2019 at 9:18 AM Maxime Ripard <mripard at kernel.org> wrote:
>
> Hi,
>
> On Thu, Sep 19, 2019 at 11:03:26PM +0300, Roman Stratiienko wrote:
> > Actually, I beleive this is True solution, and current one is wrong.  Let
> > me explain why.
> >
> > De2. 0 was designed to match Android hwcomposer hal requirements IMO.
> > You can easily agree with this conclusion by comparing Composer HAL and
> > De2. 0 hardware manuals.
> >
> > I faced at least 4 issues when try to run Android using the mainline kernel
> > sun8i mixer implementation. Current one, missing pixel formats (my previous
> > patch), missing plane alpha and rotation properties. I plan to fix it and
> > also send appropriate solution to the upstream.
> >
> > To achieve optimal UI performance Android requires at least 4 ui layers to
> > make screen composition. Current patch enables 4th plane usable.
>
> Note that you can also get 4 UI planes by enabling more than one UI
> layer per channel. You wouldn't be able to use alpha between each
> plane of a given channel, but we can use a similar trick than what we
> did for the pipes in the sun4i backend.
>
> Maxime



-- 
Best regards,
Roman Stratiienko
Global Logic Inc.