linux-kernel - Re: [RFC PATCH 0/4] PM / Domains: Add support for explicit control of PM domains

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Date:   Wed, 26 Apr 2017 10:06:20 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Jon Hunter <jonathanh@...dia.com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Stanimir Varbanov <stanimir.varbanov@...aro.org>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [RFC PATCH 0/4] PM / Domains: Add support for explicit control of
 PM domains

Hi Ulf,

On Tue, Apr 25, 2017 at 9:34 PM, Ulf Hansson <ulf.hansson@...aro.org> wrote:
> However, we currently know about at least two different SoCs that need
> this. Perhaps we can extend the below list to justify adding a new
> framework/APIs. Something along the lines what you propose in $subject
> patchset.
>
> 1) Nvidia; to solve the USB super-speed host/device problem.
> 2) QCOM, which has pointed to several cases where the PM topology is
> laid out like devices having two PM domains..
> 3?) I don't fully remember - but I think Geert also pointed to some
> examples where a device could reside in a clock domain but also in
> power domain for a Renesas SoC!?
> 4) ?

Most Renesas SoCs have module clocks, which we model as a clock domain.
Some Renesas SoCs have power domains for CPUs, others have them for
devices as well.
As we always provide a virtual "always-on" power domain in the power domain
controller, all devices can refer to it using "power-domains" properties,
and the driver for the power domain controller can just forward the clock
domain operations to the clock driver.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds