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Date:   Fri, 20 Sep 2019 08:18:00 +0200
From:   Maxime Ripard <mripard@kernel.org>
To:     Roman Stratiienko <roman.stratiienko@globallogic.com>
Cc:     Jernej =?utf-8?Q?=C5=A0krabec?= <jernej.skrabec@siol.net>,
        linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org
Subject: Re: [PATCH] drm/sun4i: Use vi plane as primary
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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

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