linux-kernel - Re: [PATCH 14/15] dt-bindings: arm-gic: Drop 'clock-names' from binding document

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Message-ID: <56EBBE38.6070303@nvidia.com>
Date:	Fri, 18 Mar 2016 08:37:12 +0000
From:	Jon Hunter <jonathanh@...dia.com>
To:	Rob Herring <robh+dt@...nel.org>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Marc Zyngier <marc.zyngier@....com>,
	Benoît Cousson <bcousson@...libre.com>,
	Tony Lindgren <tony@...mide.com>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	"Stephen Warren" <swarren@...dotorg.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Kevin Hilman <khilman@...nel.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Grygorii Strashko <grygorii.strashko@...com>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Linus Walleij <linus.walleij@...aro.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	linux-omap <linux-omap@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 14/15] dt-bindings: arm-gic: Drop 'clock-names' from
 binding document


On 17/03/16 20:14, Rob Herring wrote:
> On Thu, Mar 17, 2016 at 9:19 AM, Jon Hunter <jonathanh@...dia.com> wrote:
>> Commit afbbd2338176 ("irqchip/gic: Document optional Clock and Power
>> Domain properties") documented optional clock and power-dmoain properties
>> for the ARM GIC. Currently, there are no users of these and for the
>> Tegra210 Audio GIC (based upon the GIC-400) there are two clocks, a
>> functional clock and interface clock, that need to be enabled.
>>
>> To allow flexibility, drop the 'clock-names' from the GIC binding and
>> just provide a list of clocks which the driver can parse. It is assumed
>> that any clocks that are listed, need to be enabled in order to access
>> the GIC.
>>
>> Signed-off-by: Jon Hunter <jonathanh@...dia.com>
>>
>> ---
>>
>> Please note that I am not sure if this will be popular, but I am trying
>> to come up with a generic way to handle multiple clocks that may be
>> required for accessing a GIC.
> 
> It's not. :)
> 
> We need to specify the number and order of clocks by compatible string
> at a minimum. Sadly, ARM's GICs are well documented and include clock
> names, so you can't just make up genericish names either which is
> probably often the case.

Do you have any suggestions then?

I have had a look at the ARM TRMs and although I see that they do show
the functional clock, there is no mention of whether there are any other
clocks need in order to interface to the GIC (ie. bus clock). I know
that for other SoCs such as OMAP it is common to have both a functional
clock and interface clock. So I believe this is fairly common.

Cheers
Jon