linux-kernel - Re: [PATCH v1 3/3] ARM: tegra: cpuidle driver for tegra

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Date:	Thu, 26 Jan 2012 23:10:58 -0800
From:	Colin Cross <ccross@...roid.com>
To:	"Bedia, Vaibhav" <vaibhav.bedia@...com>
Cc:	Peter De Schrijver <pdeschrijver@...dia.com>,
	Russell King <linux@....linux.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	Olof Johansson <olof@...om.net>,
	Stephen Warren <swarren@...dia.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v1 3/3] ARM: tegra: cpuidle driver for tegra

On Thu, Jan 26, 2012 at 10:59 PM, Bedia, Vaibhav <vaibhav.bedia@...com> wrote:
> On Thu, Jan 26, 2012 at 21:52:03, Peter De Schrijver wrote:
> [...]
>> +static int tegra_idle_enter_lp3(struct cpuidle_device *dev,
>> +     struct cpuidle_driver *drv, int index)
>> +{
>> +     ktime_t enter, exit;
>> +     s64 us;
>> +
>> +     local_irq_disable();
>> +     local_fiq_disable();
>> +
>> +     enter = ktime_get();
>> +
>> +     tegra_cpu_wfi();
>> +
>> +     exit = ktime_sub(ktime_get(), enter);
>> +     us = ktime_to_us(exit);
>> +
>> +     local_fiq_enable();
>> +     local_irq_enable();
>> +
>> +     dev->last_residency = us;
>> +
>> +     return index;
>> +}
>
> You can probably drop local_irq_disable() and local_irq_enable().

local_irq_enable() is required by the cpuidle call semantics.  See
arch/arm/process.c, it has a 				WARN_ON(irqs_disabled()) after the
idle function call.  The local_irq_disable() can and probably should
be dropped, although a comment that the function is called with
interrupts off and is expected to return with interrupts on would be
helpful.
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