linux-kernel - Re: [PATCH v4 4/5] arm64: add support for ACPI Low Power Idle(LPI)

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Date:	Wed, 20 Apr 2016 11:20:59 +0100
From:	Sudeep Holla <sudeep.holla@....com>
To:	Vikas Sajjan <sajjan.linux@...il.com>
Cc:	Sudeep Holla <sudeep.holla@....com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Al Stone <al.stone@...aro.org>,
	Prashanth Prakash <pprakash@...eaurora.org>,
	Ashwin Chaugule <ashwin.chaugule@...aro.org>,
	Mark Rutland <mark.rutland@....com>,
	Vikas C Sajjan <vikas.cha.sajjan@....com>,
	Sunil V L <sunil.vl@....com>
Subject: Re: [PATCH v4 4/5] arm64: add support for ACPI Low Power Idle(LPI)



On 20/04/16 10:59, Vikas Sajjan wrote:
> Hi Sudeep,
>
> On Tue, Apr 19, 2016 at 6:00 PM, Sudeep Holla <sudeep.holla@....com> wrote:
>> This patch adds appropriate callbacks to support ACPI Low Power Idle
>> (LPI) on ARM64.
>>
>> It also selects ARCH_SUPPORTS_ACPI_PROCESSOR_LPI if ACPI is enabled
>> on ARM64.
>>

[...]

>> @@ -211,6 +214,37 @@ void __init acpi_boot_table_init(void)
>>          }
>>   }
>>
>> +int acpi_processor_ffh_lpi_probe(unsigned int cpu)
>> +{
>> +       return arm_cpuidle_init(cpu);
>> +}
>> +
>
> This is generating warning as below:
>
> WARNING: vmlinux.o(.text+0x11024): Section mismatch in reference from
> the function acpi_processor_ffh_lpi_probe() to the function
> .init.text:arm_cpuidle_init()
> The function acpi_processor_ffh_lpi_probe() references
> the function __init arm_cpuidle_init().
> This is often because acpi_processor_ffh_lpi_probe lacks a __init
> annotation or the annotation of arm_cpuidle_init is wrong.
>

I am aware of this and needs to be fixed. I posted ARM64/PSCI related
patches for completeness.

We can't have __init annotation for ..ffh_lpi_probe as it can be called
from hotplug paths in ACPI. Only solution I see is to remove __init tag
for arm_cpuidle_init. I raised similar concern on the other thread
yesterday[1]

Thanks for looking at these patches, much appreciated.

>
>> +struct acpi_processor_lpi *lpi;
>> +int acpi_processor_ffh_lpi_enter(struct acpi_processor_lpi *lpi, int idx)
>
> Wondering how are you handling with Resource Dependencies for Idle.
> I mean _RDI needs to be taken care, since the dependency between the
> power resources and the LPI state is described in _RDI.
>

Correct, right now I haven't considered RDI yet as I don't have proper
platform to test. IMO it can be added later as RDI is optional and not
used on all platforms.

-- 
Regards,
Sudeep

[1] http://lkml.iu.edu/hypermail/linux/kernel/1604.2/02181.html