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

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Message-ID: <20150306190812.11109.82130@quantum>
Date:	Fri, 06 Mar 2015 11:08:12 -0800
From:	Mike Turquette <mturquette@...aro.org>
To:	Lee Jones <lee.jones@...aro.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:	kernel@...inux.com, sboyd@...eaurora.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v3 0/4] clk: st: New always-on clock domain

Quoting Lee Jones (2015-03-04 04:00:03)
> Mike,
> 
> Do you want me to resend this set with Robert's Reviewed-by applied,
> or are you happy to apply it yourself?

No need for the resend. I am hoping for a final review from a DT human.

This approach looks fine to me. In practice I think it is restricted to
hardware blocks that don't exist in DT yet (e.g. no driver, in the case
of your interconnect) and that restriction is probably for the best.

Regards,
Mike

> 
> > 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.
> > 
> > *** BLURB HERE ***
> > 
> > Lee Jones (4):
> >   ARM: sti: stih407-family: Supply defines for CLOCKGEN A0
> >   ARM: sti: stih407-family: Add platform interconnects to always-on clk
> >     domain
> >   clk: Provide an always-on clock domain framework
> >   clk: dt: Introduce always-on clock domain documentation
> > 
> >  .../devicetree/bindings/clock/clk-always-on.txt    | 35 ++++++++++++
> >  arch/arm/boot/dts/stih407-family.dtsi              | 15 ++++++
> >  drivers/clk/Makefile                               |  1 +
> >  drivers/clk/clk-always-on.c                        | 62 ++++++++++++++++++++++
> >  include/dt-bindings/clock/stih407-clks.h           |  4 ++
> >  5 files changed, 117 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/clock/clk-always-on.txt
> >  create mode 100644 drivers/clk/clk-always-on.c
> > 
> 
> -- 
> Lee Jones
> Linaro STMicroelectronics Landing Team Lead
> Linaro.org │ Open source software for ARM SoCs
> Follow Linaro: Facebook | Twitter | Blog
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