linux-kernel - Re: CPUfreq - udelay() interaction issues

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Date:	Fri, 23 Apr 2010 19:57:30 -0700
From:	Saravana Kannan <skannan@...eaurora.org>
To:	Arjan van de Ven <arjan@...radead.org>
CC:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	cpufreq <cpufreq@...r.kernel.org>,
	linux-arm-msm <linux-arm-msm@...r.kernel.org>,
	Dave Jones <davej@...hat.com>,
	Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>,
	Thomas Renninger <trenn@...e.de>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: CPUfreq - udelay() interaction issues

Arjan van de Ven wrote:
> so in reality, all hardware that does coordination between cores/etc
> like this also has a tsc that is invariant of the actual P state.
> If there are exceptions, those have a problem, but I can't think of any
> right now.
> Once the TSC is invariant of P state, udelay() is fine, since that goes
> of the tsc, not of some delay loop kind of thing....

I assume you are talking specifically about x86. I want x86 to be 
correct, but also want ARM to be correct. So, at this point I might as 
well try to put in an arch independent fix.

Thanks,
Saravana
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