linux-kernel - Re: [PATCH v3 5/5] ACPI / processor_idle: Add support for Low Power Idle(LPI) states

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Message-ID: <570D0656.1000608@arm.com>
Date:	Tue, 12 Apr 2016 15:29:42 +0100
From:	Sudeep Holla <sudeep.holla@....com>
To:	Vikas Sajjan <sajjan.linux@...il.com>
Cc:	Sudeep Holla <sudeep.holla@....com>, linux-acpi@...r.kernel.org,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	linux-kernel@...r.kernel.org, linux-ia64@...r.kernel.org,
	x86@...nel.org, Al Stone <al.stone@...aro.org>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Mahesh Sivasubramanian <msivasub@...eaurora.org>,
	Ashwin Chaugule <ashwin.chaugule@...aro.org>,
	Prashanth Prakash <pprakash@...eaurora.org>,
	Vikas C Sajjan <vikas.cha.sajjan@....com>,
	Sunil V L <sunil.vl@....com>
Subject: Re: [PATCH v3 5/5] ACPI / processor_idle: Add support for Low Power
 Idle(LPI) states



On 12/04/16 05:06, Vikas Sajjan wrote:
> Hi Sudeep,
>
>
> On Wed, Dec 2, 2015 at 7:40 PM, Sudeep Holla <sudeep.holla@....com> wrote:

[...]

>> diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
>> index 29f787b2493f..bfc59de0ce6b 100644
>> --- a/drivers/acpi/processor_driver.c
>> +++ b/drivers/acpi/processor_driver.c
>> @@ -90,7 +90,7 @@ static void acpi_processor_notify(acpi_handle handle, u32 event, void *data)
>>                                                    pr->performance_platform_limit);
>>                  break;
>>          case ACPI_PROCESSOR_NOTIFY_POWER:
>> -               acpi_processor_cst_has_changed(pr);
>> +               acpi_processor_power_state_has_changed(pr);
>
> The function  acpi_processor_power_state_has_changed() has a check as below,
>
>   if (nocst)
>             return -ENODEV;
>
> So was wondering if the platform supports only _LPI and  _CST is not
> supported, the 'nocst' module param passed will be 1,
> and function will return -ENODEV.
>

You are right, it needs to be handled correctly. Thanks for spotting this.

> Hence, with the introduction of LPI, should we be handling "nocst"
> appropriately.
> Similar is the case in function  int acpi_processor_hotplug(struct
> acpi_processor *pr);
>

Correct.

> Let me know, if i am missing something here.
>

I don't think so. Once again thanks for the review.

-- 
Regards,
Sudeep