linux-kernel - Re: [PATCH v3] ARM: tegra: cpuidle: implement cpuidle_state.enter

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Date:	Wed, 20 May 2015 10:55:41 +0200
From:	Tomeu Vizoso <tomeu.vizoso@...labora.com>
To:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
CC:	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Russell King <linux@....linux.org.uk>,
	Stephen Warren <swarren@...dotorg.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Alexandre Courbot <gnurou@...il.com>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Ingo Molnar <mingo@...nel.org>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] ARM: tegra: cpuidle: implement cpuidle_state.enter_freeze()

On 05/20/2015 10:44 AM, Lorenzo Pieralisi wrote:
> On Tue, May 19, 2015 at 03:49:12PM +0100, Tomeu Vizoso wrote:
>> This callback is expected to do the same as enter() but it has to
>> guarantee that interrupts aren't enabled at any point in its execution,
>> as the tick is frozen.
>>
>> It will be called when the system goes to suspend-to-idle and will
>> reduce power usage because CPUs won't be awaken for unnecessary IRQs.
>>
>> By setting the CPUIDLE_FLAG_TIMER_STOP flag, we can reuse the same code
>> for both the enter() and enter_freeze() callbacks.
>>
>> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@...labora.com>
>> Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>
>> ---
>>
>> v3:	* Set CPUIDLE_FLAG_TIMER_STOP to simplify things as suggested by
>> 	Lorenzo Pieralisi
>> v2:	* Disable FIQs also when suspending-to-idle
>> ---
>>  arch/arm/mach-tegra/cpuidle-tegra114.c | 13 +++++++++----
>>  1 file changed, 9 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/arm/mach-tegra/cpuidle-tegra114.c b/arch/arm/mach-tegra/cpuidle-tegra114.c
>> index 155807f..7e59ac0 100644
>> --- a/arch/arm/mach-tegra/cpuidle-tegra114.c
>> +++ b/arch/arm/mach-tegra/cpuidle-tegra114.c
>> @@ -44,16 +44,12 @@ static int tegra114_idle_power_down(struct cpuidle_device *dev,
>>  	tegra_set_cpu_in_lp2();
>>  	cpu_pm_enter();
>>  
>> -	tick_broadcast_enter();
>> -
>>  	call_firmware_op(prepare_idle);
>>  
>>  	/* Do suspend by ourselves if the firmware does not implement it */
>>  	if (call_firmware_op(do_idle, 0) == -ENOSYS)
>>  		cpu_suspend(0, tegra30_sleep_cpu_secondary_finish);
>>  
>> -	tick_broadcast_exit();
>> -
>>  	cpu_pm_exit();
>>  	tegra_clear_cpu_in_lp2();
>>  
>> @@ -61,6 +57,13 @@ static int tegra114_idle_power_down(struct cpuidle_device *dev,
>>  
>>  	return index;
>>  }
>> +
>> +static void tegra114_idle_enter_freeze(struct cpuidle_device *dev,
>> +				       struct cpuidle_driver *drv,
>> +				       int index)
>> +{
>> +       tegra114_idle_power_down(dev, drv, index);
>> +}
> 
> You do not need this function, remove it and update the enter_freeze
> pointer below with tegra114_idle_power_down please.

How so? The callbacks have different signatures.

Regards,

Tomeu

> Thanks,
> Lorenzo
> 
>>  #endif
>>  
>>  static struct cpuidle_driver tegra_idle_driver = {
>> @@ -72,8 +75,10 @@ static struct cpuidle_driver tegra_idle_driver = {
>>  #ifdef CONFIG_PM_SLEEP
>>  		[1] = {
>>  			.enter			= tegra114_idle_power_down,
>> +			.enter_freeze		= tegra114_idle_enter_freeze,
>>  			.exit_latency		= 500,
>>  			.target_residency	= 1000,
>> +			.flags			= CPUIDLE_FLAG_TIMER_STOP,
>>  			.power_usage		= 0,
>>  			.name			= "powered-down",
>>  			.desc			= "CPU power gated",
>> -- 
>> 2.4.1
>>

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