linux-kernel - Re: [PATCH v3 0/4] clk: st: New always-on clock domain

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Date:	Fri, 27 Feb 2015 22:37:10 +0100
From:	Robert Jarzmik <robert.jarzmik@...e.fr>
To:	Lee Jones <lee.jones@...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: [PATCH v3 0/4] clk: st: New always-on clock domain

Lee Jones <lee.jones@...aro.org> writes:

> v2 => v3:
>   - Ensure DT actually reflects h/w
>     - i.e. Nodes should not contain a mishmash of different IP
>       blocks, but should identify related h/w.  In the current
>       example we use interconnects
>   - Change naming from clkdomain to clk-always-on
>   - Place "do not abuse" warning in documentation
>
> v1 => v2:
>   - Turned the ST specific driver into a generic one
>   
> Hardware can have a bunch of clocks which must not 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 turn them off and the hardware will
> subsequently die.  The only way to recover from this failure is to
> restart.
>   
> To avoid either of these two scenarios from catastrophically
> disabling the running system we have implemented a clock domain
> where clocks are consumed and references are taken, thus preventing
> them from being shut down by the framework.

Hi Lee,

I wonder why there is a need for a new clock when CLK_IGNORE_UNUSED does
exist. What is the usecase that is covered by this patchset which is not used by
CLK_IGNORE_UNUSED clock flag ?

And if that reason exists, I'd like to find it in the commit message.

Cheers.

--
Robert
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