linux-kernel - Re: [PATCH v5] clocksource: arch_timer: Fix code to use physical timers when requested

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Message-ID: <1418203166.21309.3.camel@mtksdaap41>
Date:	Wed, 10 Dec 2014 17:19:26 +0800
From:	Yingjoe Chen <yingjoe.chen@...iatek.com>
To:	Catalin Marinas <catalin.marinas@....com>
CC:	Marc Zyngier <Marc.Zyngier@....com>,
	Sonny Rao <sonnyrao@...omium.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Mark Rutland <Mark.Rutland@....com>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Russell King <linux@....linux.org.uk>,
	Sudeep Holla <Sudeep.Holla@....com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Will Deacon <Will.Deacon@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>,
	"dianders@...omium.org" <dianders@...omium.org>,
	Olof Johansson <olof@...om.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Eddie Huang (黃智傑) 
	<eddie.huang@...iatek.com>, Liviu Dudau <Liviu.Dudau@....com>
Subject: Re: [PATCH v5] clocksource: arch_timer: Fix code to use physical
 timers when requested

On Tue, 2014-12-09 at 16:58 +0000, Catalin Marinas wrote:
<...>
> You mix timer and counter terms here. Anyway, of we use physical timer,
> you could argue that it makes sense to use the corresponding physical
> counter (CNTPCT). However, on arm64 we only expose CNTVCT to user VDSO
> and we want to use the same in the kernel. When booting at EL2, CNTVCT
> == CNTPCT because we control CNTVOFF, that's unless we have some broken
> firmware that does not restore CNTVOFF correctly. That's what we want
> to spot early, hence the aim to always use the virtual counter (but not
> the timer, use use the physical timer as it makes it easier for KVM).
> 
> So the patch below, on top of linux-next, should solve the BUG():

Thanks for detail explanation and the patch. I tested it on my platform
and it did solve the issue. So,

Tested-by: Yingjoe Chen <yingjoe.chen@...iatek.com>

Joe.C


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