linux-kernel - Re: [STLinux Kernel] [PATCH 0/4] clk: Provide support for always-on clocks

Open Source and information security mailing list archives

Message-ID: <20150402105803.GD9447@x1>
Date:	Thu, 2 Apr 2015 11:58:03 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Gabriel Fernandez <gabriel.fernandez@...aro.org>
Cc:	Peter Griffin <peter.griffin@...aro.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Mike Turquette <mturquette@...aro.org>,
	"kernel@...inux.com" <kernel@...inux.com>, sboyd@...eaurora.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [STLinux Kernel] [PATCH 0/4] clk: Provide support for always-on
 clocks

> With these series as they are, we need  'clk_ignore_unused'  on
> sthi407-b2120.dts and stih418-b2199.dts.
> 
> We have to modificate stih407-clock.dtsi and stih418-clock.dtsi in same way.

Just to clarify this point for all interested parties; this patch-set
is not the completed article.  It's purpose is to add the core
functionality and the documentation _only_.  The STiH410 support is
only provided in this set as an example of how the bindings are to be
used.  Other platforms are to be enabled subsequently as part of a
different submission.

> On 2 April 2015 at 10:12, Peter Griffin <peter.griffin@...aro.org> wrote:
> > Hi Lee,
> >
> > On Fri, 27 Feb 2015, Lee Jones wrote:
> >
> >> Some hardware contains bunches of clocks which must never be
> >> turned off.  If drivers a) fail to obtain a reference to any
> >> of these or b) give up a previously obtained reference
> >> during suspend, the common clk framework will attempt to
> >> disable them and a platform can fail irrecoverably as a
> >> result.  Usually the only way to recover from these failures
> >> is to reboot.
> >>
> >> To avoid either of these two scenarios from catastrophically
> >> disabling an otherwise perfectly healthy running system,
> >> clocks can be identified as always-on using this property
> >> from inside a clocksource's node.  The CLK_IGNORE_UNUSED
> >> flag will be applied to each clock instance named in this
> >> property, thus preventing them from being shut down by the
> >> framework.
> >
> > Great stuff.
> >
> > One minor comment is that assuming this works on stih407 and stih410
> > to the extent that the platform can now boot without clk_ignore_unused
> > kenel parameter then you should have an additional patch to remove
> > clk_ignore_unused from the default bootargs in stih407-b2120.dts and
> > stih410-b2120.dts files.
> >
> > Maxime - Is it possible for you to test this series on stih418-b2199 as
> > a well? As it could most likely also be removed from stih418-b2199.dts file
> > to, but neither Lee or myself have the hardware to test.
> >
> > Apart from that, for the series: -
> >  Acked-by: Peter Griffin <peter.griffin@...aro.org>
> >
> > regards,
> >
> > Peter.
> >
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel@...ts.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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