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

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Message-ID: <57716962.1040106@arm.com>
Date:	Mon, 27 Jun 2016 18:58:58 +0100
From:	Sudeep Holla <sudeep.holla@....com>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>,
	"Rafael J . Wysocki" <rjw@...ysocki.net>
Cc:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Sudeep Holla <sudeep.holla@....com>,
	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)



On 27/06/16 18:07, Sudeep Holla wrote:
>
>
> On 27/06/16 17:29, Daniel Lezcano wrote:

[...]

>>
>> acpi_disabled - acpi_disabled - acpi_disabled everywhere :/
>>
>> The enable-method approach is not straightforward and now it is polluted
>> by acpi-disabled.
>>
>> So IIUC,
>>
>> smp_init_cpus (contains acpi_disabled)
>>    smp_cpu_setup
>>      cpu_read_ops
>>        cpu_read_enable_method (contains acpi_disabled)
>>          acpi_get_enable_method (returns 'psci' after checking
>> psci_is_present)
>>
>> Then psci_cpu_init_idle is called... and check again acpi_disabled.
>>
>> IMO, the circumlocution with the psci vs acpi vs acpi_disabled is
>> getting unnecessary too complex, is prone to error and will lead to
>> unmaintainable code very soon.
>>
>> I suggest to sort out encapsulation and self-contained code before
>> adding more feature in this area.
>>
>
> I understand your concern but I have no idea on how to clean up. Lorenzo
> asked to factor our common code between psci_{dt,acpi}_cpu_init_idle and
> I think you might not like the refactoring[1]. I didn't want to change
> cpuidle_ops and hence psci_dt_cpu_init_idle parameters. I will see if
> changing that simplifies things.
>

One of the reasons for adding acpi_disabled check is to keep the other
logic at the same place. Otherwise we end up duplicating that code which
is what I have done in psci_{dt,acpi}_cpu_init_idle at the first place.

-- 
Regards,
Sudeep