From: Mike Turquette <mturquette@linaro.org>
To: Arnd Bergmann <arnd@arndb.de>, linux-arm-kernel@lists.infradead.org
Cc: "Grygorii Strashko" <grygorii.strashko@ti.com>,
"Geert Uytterhoeven" <geert@linux-m68k.org>,
"Kevin Hilman" <khilman@kernel.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
"Ulf Hansson" <ulf.hansson@linaro.org>,
"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
"Dmitry Torokhov" <dmitry.torokhov@gmail.com>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Grant Likely" <grant.likely@secretlab.ca>,
"Rob Herring" <robh+dt@kernel.org>,
ssantosh@kernel.org
Subject: Re: [PATCH v4 1/2] ARM: keystone: pm: switch to use generic pm domains
Date: Mon, 24 Nov 2014 22:44:06 -0800 [thread overview]
Message-ID: <20141125064406.12298.57929@quantum> (raw)
In-Reply-To: <2997659.fTX2lvxXfH@wuerfel>
Quoting Arnd Bergmann (2014-11-24 02:50:28)
> On Friday 21 November 2014 20:58:01 Grygorii Strashko wrote:
> > Hi Kevin,
> > On 11/21/2014 10:06 AM, Geert Uytterhoeven wrote:
> > > On Fri, Nov 21, 2014 at 2:30 AM, Kevin Hilman <khilman@kernel.org> wrote:
> > >> Geert Uytterhoeven <geert@linux-m68k.org> writes:
> > >>
> > >> So now I'm confused about why the PM domain has to do anything special
> > >> if the presence/absence of the clocks is already handled by the DT.
> > >
> > > Just adding a clock property to a device node in DT doesn't enable the clock
> > > automatically, nor make it runtime-managed automatically.
> > > Compare this to e.g. pinctrl, where adding pinctrl properties to DT does enable
> > > them automatically, without the driver for the device having to care about it.
> > >
> > > Drivers interfacing external hardware typically do care about clocks, as they
> > > have to program clock generators for the external hardware interface (e.g.
> > > driving spi or i2c buses at specific frequencies).
>
> But is this a property of the driver or of the device? If this is true
> independent of the driver implementation, I don't see a problem with
> the approach of linking to a power-domain that automatically manages
> all clocks for the devices that need this, and requires the driver to
> manage them itself when there are any clocks that can't be handled
> with the generic clk-power-domain implementation.
>
> >
> > In non-DT case, we have possibility to divide clocks on "fck" and "opt"
> > (The way it can be done is not convenient, but it is - .con_id).
> >
> > For DT-case - no way now. Also, PM domains are not physically present on
> > Keystone 2 and GPD was selected as glue layer to integrate DT, pm_clk and
> > PM runtime all together (one big-fat-global PM domain :).
> >
> > So, I was able to find only following way to define "fck" clocks in DT:
> > clocks = <&papllclk>, <&clkcpgmac>, <&chipclk12>;
> > clock-names = "clk_pa", "clk_cpgmac", "cpsw_cpts_rft_clk";
> > fck-clocks = <&papllclk>, <&clkcpgmac>;
> > As you can see - this will lead to data duplication in DT (
> >
> > Any propositions are welcome?
> >
> > Unfortunately, It seems that if we would not able to find DT solution
> > then there will be following ways to move forward:
> > - "remove the power domain proxy from your drivers and use the clocks directly"
> > ((c) Arnd Bergmann).
> > [As possibility - It can be allowed to use clk_pm APIs by drivers]
> > - continue using platform specific implementations.
>
> Could the driver maybe identify the clocks that it wants to manage itself
> to the pm-domain code? If it's safe for a device to have the clock turned
> on at the default rate before loading the driver, any device that is connected
> to the simple clk-pm-domain code could have all its clocks start out as
> owned by the pm-domain, but then claim the clocks it needs to reprogram for
> itself and take them out of the pmdomain.
I was thinking along similar lines. The functional versus optional stuff
is really a property of the consuming device, not the clock signal
itself.
Instead of adding a new property to the clock binding (e.g. fck-clocks
or optional-clocks), could we simply wrap those lists of clocks in
another node? E.g:
mandatory-clocks {
clocks = <&papllclk>, <&clkcpgmac>;
clock-names = "clk_pa", "clk_cpgmac";
}
clocks = <&papllclk>, <&clkcpgmac>, <&chipclk12>;
clocks = <&clkcpgmac>;
clock-names = "cpsw_cpts_rft_clk";
}
I'm showing my DT ignorance on this one. I haven't really thought
through how these sub-nodes would work with of_clk_* handlers in
drivers/clk/clkdev.c.
Regards,
Mike
>
> Arnd
> --
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next prev parent reply other threads:[~2014-11-25 6:44 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-10 14:59 [PATCH v4 0/2] ARM: keystone: pm: switch to use generic pm domains Grygorii Strashko
2014-11-10 14:59 ` [PATCH v4 1/2] " Grygorii Strashko
2014-11-10 15:06 ` Arnd Bergmann
2014-11-10 17:38 ` Grygorii Strashko
2014-11-10 20:36 ` Arnd Bergmann
2014-11-17 19:14 ` Kevin Hilman
2014-11-17 20:37 ` Arnd Bergmann
2014-11-17 21:50 ` Kevin Hilman
2014-11-18 18:54 ` Grygorii Strashko
2014-11-18 19:32 ` Arnd Bergmann
2014-11-19 11:32 ` Grygorii Strashko
2014-11-19 13:47 ` Arnd Bergmann
2014-11-20 11:34 ` Ulf Hansson
2014-11-20 12:03 ` Grygorii Strashko
2014-11-20 13:12 ` Ulf Hansson
2014-11-20 13:32 ` Geert Uytterhoeven
2014-11-20 15:32 ` Grygorii Strashko
2014-11-20 20:22 ` Kevin Hilman
2014-11-20 20:26 ` Geert Uytterhoeven
2014-11-20 21:48 ` Kevin Hilman
2014-11-20 21:54 ` Geert Uytterhoeven
2014-11-21 1:30 ` Kevin Hilman
2014-11-21 8:06 ` Geert Uytterhoeven
2014-11-21 18:58 ` Grygorii Strashko
2014-11-21 19:29 ` Kevin Hilman
2014-11-21 20:14 ` Grygorii Strashko
2014-11-24 10:50 ` Arnd Bergmann
2014-11-25 6:44 ` Mike Turquette [this message]
2014-11-25 10:33 ` Arnd Bergmann
2014-11-25 11:08 ` Grygorii Strashko
2014-11-25 12:09 ` Arnd Bergmann
2014-11-25 13:30 ` Grygorii Strashko
2014-11-25 14:04 ` Russell King - ARM Linux
2014-11-25 14:53 ` Grygorii Strashko
2014-11-25 16:28 ` santosh shilimkar
2014-11-21 19:20 ` Kevin Hilman
2014-11-21 9:04 ` Geert Uytterhoeven
2014-11-18 2:18 ` santosh.shilimkar
2014-11-10 14:59 ` [PATCH v4 2/2] ARM: dts: keystone: add generic pm controller node Grygorii Strashko
2014-11-10 15:13 ` [PATCH v4 0/2] ARM: keystone: pm: switch to use generic pm domains Grygorii Strashko
2014-11-10 18:51 ` santosh.shilimkar
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