linux-kernel - Re: [PATCH 1/2] PPC: powernv: remove redundant cpuidle_idle

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Date:	Fri, 07 Feb 2014 16:30:44 +0530
From:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>
To:	Deepthi Dharwar <deepthi@...ux.vnet.ibm.com>
CC:	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linuxppc-dev@...ts.ozlabs.org,
	Linux ARM Kernel ML <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/2] PPC: powernv: remove redundant cpuidle_idle_call()

Hi Deepthi,

On 02/07/2014 03:15 PM, Deepthi Dharwar wrote:
> Hi Preeti,
> 
> Thanks for the patch.
> 
> On 02/07/2014 12:31 PM, Preeti U Murthy wrote:
>> Hi Nicolas,
>>
>> Find below the patch that will need to be squashed with this one.
>> This patch is based on the mainline.Adding Deepthi, the author of
>> the patch which introduced the powernv cpuidle driver. Deepthi,
>> do you think the below patch looks right? We do not need to do an
>> explicit local_irq_enable() since we are in the call path of
>> cpuidle driver and that explicitly enables irqs on exit from
>> idle states.
> 
> Yes, We enable irqs explicitly while entering snooze loop and we always
> have interrupts enabled in the snooze state.
> For NAP state, we exit out of this state with interrupts enabled so we
> do not need an explicit enable of irqs.
> 
>> On 02/07/2014 06:47 AM, Nicolas Pitre wrote:
>>> On Thu, 6 Feb 2014, Preeti U Murthy wrote:
>>>
>>>> Hi Daniel,
>>>>
>>>> On 02/06/2014 09:55 PM, Daniel Lezcano wrote:
>>>>> Hi Nico,
>>>>>
>>>>>
>>>>> On 6 February 2014 14:16, Nicolas Pitre <nicolas.pitre@...aro.org> wrote:
>>>>>
>>>>>> The core idle loop now takes care of it.
>>>>>>
>>>>>> Signed-off-by: Nicolas Pitre <nico@...aro.org>
>>>>>> ---
>>>>>>  arch/powerpc/platforms/powernv/setup.c | 13 +------------
>>>>>>  1 file changed, 1 insertion(+), 12 deletions(-)
>>>>>>
>>>>>> diff --git a/arch/powerpc/platforms/powernv/setup.c
>>>>>> b/arch/powerpc/platforms/powernv/setup.c
>>>>>> index 21166f65c9..a932feb290 100644
>>>>>> --- a/arch/powerpc/platforms/powernv/setup.c
>>>>>> +++ b/arch/powerpc/platforms/powernv/setup.c
>>>>>> @@ -26,7 +26,6 @@
>>>>>>  #include <linux/of_fdt.h>
>>>>>>  #include <linux/interrupt.h>
>>>>>>  #include <linux/bug.h>
>>>>>> -#include <linux/cpuidle.h>
>>>>>>
>>>>>>  #include <asm/machdep.h>
>>>>>>  #include <asm/firmware.h>
>>>>>> @@ -217,16 +216,6 @@ 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();
>>>>>> -       }
>>>>>>
>>
>>  drivers/cpuidle/cpuidle-powernv.c |    4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
>> index 78fd174..130f081 100644
>> --- a/drivers/cpuidle/cpuidle-powernv.c
>> +++ b/drivers/cpuidle/cpuidle-powernv.c
>> @@ -31,11 +31,13 @@ static int snooze_loop(struct cpuidle_device *dev,
>>  	set_thread_flag(TIF_POLLING_NRFLAG);
>>
>>  	while (!need_resched()) {
>> +		ppc64_runlatch_off();
>                 ^^^^^^^^^^^^^^^
> We could move this before the while() loop.
> It would ideal to turn off latch when we enter snooze and
> turn it on when we are about to exit, rather than doing
> it over and over in the while loop.

You are right, this can be moved out of the loop.

Thanks

Regards
Preeti U Murthy

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