Subject: Re: [PATCH 2/3] cpuidle/powernv: Enable idle powernv cpu to call into the cpuidle framework.

From: Daniel Lezcano <[email-masked]>
Date: Mon, 29 Jul 2013 16:44:46 +0200

On 07/29/2013 04:27 PM, Deepthi Dharwar wrote:
> On 07/27/2013 10:59 AM, Daniel Lezcano wrote:
>> On 07/23/2013 11:01 AM, Deepthi Dharwar wrote:
>>> This patch enables idle powernv cpu to hook on to the cpuidle
>>> framework, if available, else call on to default idle platform
>>> code.
>>
>> Why do you need to do that ?
>>
> 
> Hi Daniel,
> 
> Well, this is needed in case when one does not compile with CPU_IDLE
> config option.
> 
> When CPUIDLE is not configured, idle cpus are needed to be running some
> sort of default idle code or loop ( in the worst case) if cpuidle driver
> is not registered or if one decides not to have that config enabled.

Hi Deepthi,

ok may be there is some difference with the other platform but the
arch_cpu_idle function defined in the other archs do:

void arch_cpu_idle(void)
{
        if (cpuidle_idle_call())
                x86_idle();
        else
                local_irq_enable();
}

or

void arch_cpu_idle(void)
{
        if (cpuidle_idle_call())
                default_idle();
}

When the cpuidle driver is not compiled or not loaded, cpuidle_idle_call
fails, falling back to the default idle function.

The arch_cpu_idle function is called from the generic code in
kernel/cpu/idle.c.

Is there a particular reason to do it in a different way ?

Thanks
  -- Daniel

>>
>>> Signed-off-by: Deepthi Dharwar <[email-masked]>
>>> ---
>>>  arch/powerpc/platforms/powernv/setup.c |   12 +++++++++++-
>>>  1 file changed, 11 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c
>>> index 84438af..97d0951 100644
>>> --- a/arch/powerpc/platforms/powernv/setup.c
>>> +++ b/arch/powerpc/platforms/powernv/setup.c
>>> @@ -25,6 +25,7 @@
>>>  #include <linux/of.h>
>>>  #include <linux/interrupt.h>
>>>  #include <linux/bug.h>
>>> +#include <linux/cpuidle.h>
>>>  
>>>  #include <asm/machdep.h>
>>>  #include <asm/firmware.h>
>>> @@ -196,6 +197,15 @@ static int __init pnv_probe(void)
>>>  	return 1;
>>>  }
>>>  
>>> +void powernv_idle(void)
>>> +{
>>> +	/* Hook to cpuidle framework if available, else
>>> +	 * call on default platform idle code
>>> +	 */
>>> +	if (cpuidle_idle_call())
>>> +		power7_idle();
>>> +}
>>> +
>>>  define_machine(powernv) {
>>>  	.name			= "PowerNV",
>>>  	.probe			= pnv_probe,
>>> @@ -205,7 +215,7 @@ define_machine(powernv) {
>>>  	.show_cpuinfo		= pnv_show_cpuinfo,
>>>  	.progress		= pnv_progress,
>>>  	.machine_shutdown	= pnv_shutdown,
>>> -	.power_save             = power7_idle,
>>> +	.power_save             = powernv_idle,
>>>  	.calibrate_decr		= generic_calibrate_decr,
>>>  #ifdef CONFIG_KEXEC
>>>  	.kexec_cpu_down		= pnv_kexec_cpu_down,
>>>
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>>> the body of a message to [email-masked]
>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>> Please read the FAQ at  http://www.tux.org/lkml/
>>>
>>
>>
> 

-- 
 <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs

Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog