linux-kernel - Re: [PATCH v6 4/5] arm64: add support for ACPI Low Power Idle(LPI)

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Message-ID: <5770F6EF.3080902@arm.com>
Date:	Mon, 27 Jun 2016 10:50:39 +0100
From:	Sudeep Holla <sudeep.holla@....com>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc:	Sudeep Holla <sudeep.holla@....com>,
	"Rafael J . Wysocki" <rjw@...ysocki.net>,
	linux-acpi@...r.kernel.org,
	Vikas Sajjan <vikas.cha.sajjan@....com>,
	Sunil <sunil.vl@....com>,
	Prashanth Prakash <pprakash@...eaurora.org>,
	Al Stone <al.stone@...aro.org>,
	Ashwin Chaugule <ashwin.chaugule@...aro.org>,
	linux-kernel@...r.kernel.org, Mark Rutland <mark.rutland@....com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v6 4/5] arm64: add support for ACPI Low Power Idle(LPI)

Hi, Daniel,

On 24/06/16 22:04, Daniel Lezcano wrote:

[...]

>>> +
>>> +    psci_states = kcalloc(count, sizeof(*psci_states), GFP_KERNEL);
>>> +    if (!psci_states)
>>> +        return -ENOMEM;
>>> +
>>> +    for (i = 0; i < count; i++) {
>>> +        u32 state;
>>> +
>>> +        lpi = &pr->power.lpi_states[i + 1];
>>> +        state = lpi->address & 0xFFFFFFFF;
>
> Why is needed to mask 'address' ?
>

This is as per Section 3.1.1 FFH Usage in LPI state entry methods in [1]

[...]

>>>   int psci_cpu_init_idle(unsigned int cpu)
>>>   {
>>>       struct device_node *cpu_node;
>>>       int ret;
>>>
>>> +    if (!acpi_disabled)
>>> +        return psci_acpi_cpu_init_idle(cpu);
>
> Is it possible the case where there is information in both the DT and in
> ACPI ? So ACPI is enabled without idle information which is in the DT ?
>

No, as Rafael mentioned aready.

>>
>> Either you do this, or we have to add it somehow somewhere in
>> drivers/cpuidle to avoid duplicating it.
>>
>> @Daniel: do you have an opinion on this please ?
>
> Yes, this function should be added to avoid duplication.
>

So, I assume you are happy with the way it's handled in this patch ?
(I will rename the file as suggested by Lorenzo)

-- 
Regards,
Sudeep

[1] 
http://infocenter.arm.com/help/topic/com.arm.doc.den0048a/DEN0048A_ARM_FFH_Specification.pdf