linux-kernel - Re: [PATCH 1/5] clk: inherit clocks enabled by bootloader

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Date:   Mon, 1 Jul 2019 12:05:40 -0700
From:   Rob Clark <robdclark@...il.com>
To:     Eric Anholt <eric@...olt.net>
Cc:     dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Rob Clark <robdclark@...omium.org>,
        aarch64-laptops@...ts.linaro.org,
        Linux PM <linux-pm@...r.kernel.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andy Gross <agross@...nel.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        linux-clk <linux-clk@...r.kernel.org>
Subject: Re: [PATCH 1/5] clk: inherit clocks enabled by bootloader

On Mon, Jul 1, 2019 at 11:25 AM Eric Anholt <eric@...olt.net> wrote:
>
> Rob Clark <robdclark@...il.com> writes:
>
> > From: Rob Clark <robdclark@...omium.org>
> >
> > The goal here is to support inheriting a display setup by bootloader,
> > although there may also be some non-display related use-cases.
> >
> > Rough idea is to add a flag for clks and power domains that might
> > already be enabled when kernel starts, and which should not be
> > disabled at late_initcall if the kernel thinks they are "unused".
> >
> > If bootloader is enabling display, and kernel is using efifb before
> > real display driver is loaded (potentially from kernel module after
> > userspace starts, in a typical distro kernel), we don't want to kill
> > the clocks and power domains that are used by the display before
> > userspace starts.
> >
> > Signed-off-by: Rob Clark <robdclark@...omium.org>
>
> Raspberry Pi is carrying downstream hacks to do similar stuff, and it
> would be great to see CCF finally support this.

yeah, both this and the multiple-possible-panel thing are a big source
of downstream hacks on basically every android device too.. :-/

it certainly would be nice to have upstream solutions for these
problems to give downstream hacks a reason not to exist

BR,
-R