linux-kernel - Re: [PATCH v6 5/5] ACPI : enable ACPI_PROCESSOR

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Message-ID: <57714043.5020207@arm.com>
Date:	Mon, 27 Jun 2016 16:03:31 +0100
From:	Sudeep Holla <sudeep.holla@....com>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>,
	"Rafael J . Wysocki" <rjw@...ysocki.net>,
	linux-acpi@...r.kernel.org
Cc:	Sudeep Holla <sudeep.holla@....com>,
	Vikas Sajjan <vikas.cha.sajjan@....com>,
	Sunil <sunil.vl@....com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Prashanth Prakash <pprakash@...eaurora.org>,
	Al Stone <al.stone@...aro.org>,
	Ashwin Chaugule <ashwin.chaugule@...aro.org>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v6 5/5] ACPI : enable ACPI_PROCESSOR_IDLE on ARM64

Hi Daniel,

On 27/06/16 15:33, Daniel Lezcano wrote:
> On 06/14/2016 04:48 PM, Sudeep Holla wrote:
>> Now that ACPI processor idle driver supports LPI(Low Power Idle), lets
>> enable ACPI_PROCESSOR_IDLE for ARM64 too.
>>
>> This patch just removes the IA64 and X86 dependency on
>> ACPI_PROCESSOR_IDLE
>>
>> Cc: linux-arm-kernel@...ts.infradead.org
>> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
>> Signed-off-by: Sudeep Holla <sudeep.holla@....com>
>> ---
>
> Hi Sudeep,
>
> now that ACPI processor supports ARM64 did you check the
> CPUIDLE_DRIVER_STATE_START trick in the code and its derivative ?
>

No, that is used only for C-State and ARM64 doesn't support it.
Patch 1/5 puts all the C-State code under #ifdef so that it's not
compiled on ARM64.

> I deleted the patch 2/5 but there is a place where:
>

Sorry, I don't follow what you mean by that.

> if (max_cstate=0)
>      max_cstate=1;
>
> Probably this is because the POLL state is inserted, so there is always
> an idle state. But for ARM, that is not the case.
>

Yes

> Also, there are some places where the idle state index begins to 1. I
> think it should be 0 for ARM.
>

Yes for LPI, it does start from 0.

-- 
Regards,
Sudeep