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

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Date:	Thu, 2 Apr 2015 11:52:09 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Peter Griffin <peter.griffin@...aro.org>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	mturquette@...aro.org, sboyd@...eaurora.org, kernel@...inux.com,
	devicetree@...r.kernel.org
Subject: Re: [STLinux Kernel] [PATCH 0/4] clk: Provide support for always-on
 clocks

On Thu, 02 Apr 2015, Peter Griffin 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.

It's already on my TODO list:

TODO:
  - Clock Domain
    - Once the clk domain driver has been accepted, remove early returns in SPI driver
    - Remove clk_ignore_unused from the DT files
    - Add LMI1 clk to STiH418

> 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.

Take a look at the third item on my TODO. :)

Yes Maxime, if you can test the set once I've completed item 3, that
would be splendid.

> Apart from that, for the series: -
>  Acked-by: Peter Griffin <peter.griffin@...aro.org>

Thanks Peter.

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