linux-kernel - Re: [PATCH v1] ARM: clocksource: make ARM_GLOBAL

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Message-ID: <20160427104110.GU5783@n2100.arm.linux.org.uk>
Date:	Wed, 27 Apr 2016 11:41:10 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Grygorii Strashko <grygorii.strashko@...com>
Cc:	Liviu Dudau <liviu.dudau@....com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>,
	linux-arm-kernel@...ts.infradead.org, Sekhar Nori <nsekhar@...com>,
	linux-omap@...r.kernel.org, Tony Lindgren <tony@...mide.com>,
	bcm-kernel-feedback-list@...adcom.com,
	linux-kernel@...r.kernel.org, linux-rockchip@...ts.infradead.org,
	kernel@...inux.com, linux-arm-kernel@...s.com,
	Florian Fainelli <f.fainelli@...il.com>,
	Wei Xu <xuwei5@...ilicon.com>, Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <kernel@...gutronix.de>,
	Srinivas Kandagatla <srinivas.kandagatla@...il.com>,
	Maxime Coquelin <maxime.coquelin@...com>,
	Masahiro Yamada <yamada.masahiro@...ionext.com>,
	Sudeep Holla <sudeep.holla@....com>,
	Jun Nie <jun.nie@...aro.org>,
	Michal Simek <michal.simek@...inx.com>,
	Jesper Nilsson <jesper.nilsson@...s.com>,
	Lars Persson <lars.persson@...s.com>,
	Mike Looijmans <mike.looijmans@...ic.nl>
Subject: Re: [PATCH v1] ARM: clocksource: make ARM_GLOBAL_TIMER selectable

On Tue, Apr 26, 2016 at 10:35:08PM +0300, Grygorii Strashko wrote:
> On 04/26/2016 07:02 PM, Liviu Dudau wrote:
> > Well, SoC-B has the GT *and* the DT node, so what is the problem with
> > enabling it for SoC-B? If there are reasons not to use the Global Timer
> > on SoC-B, surely a better option would be to mark it in DT with status = "disabled";
> 
> This was rejected [2]. DT describes HW and if it is functional the status = "disabled"
> is not good choice.
> ARM GT can't be used as clocksource/sched_clock/clockevent when CPUFreq or
> CPUIdle are enabled :(, and this is Linux specific functionality and
> not HW description. 

Sorry, but we don't want to have to disable drivers in the kernel just
because one platform has a problem (consider the single zImage case
where it may be required that the global timer is enabled for some
platform to boot - it becomes mandatory in single zImage at that point.)

Maybe a linux-specific property is needed here - "linux,low-power-unstable"
or something like that?

-- 
RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/
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