linux-kernel - Re: [PATCH v2 0/5] CPU PM notifiers

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Message-ID: <4E65ACF7.90501@ti.com>
Date:	Tue, 06 Sep 2011 10:47:43 +0530
From:	Santosh <santosh.shilimkar@...com>
To:	Shawn Guo <shawn.guo@...escale.com>
CC:	linux-arm-kernel@...ts.infradead.org, khilman@...com,
	linux@....linux.org.uk, linux-kernel@...r.kernel.org, rjw@...k.pl,
	ccross@...roid.com
Subject: Re: [PATCH v2 0/5] CPU PM notifiers

On Tuesday 06 September 2011 08:04 AM, Shawn Guo wrote:
> On Sat, Sep 03, 2011 at 08:09:10PM +0530, Santosh Shilimkar wrote:
>> Updates V2:
>> - The CPU PM notifiers are moved to generic level instead of keeping
>>    it ARM specific as per Rafael's comment.
>> - To avoid every driver duplicating the sys-core ops and cpu pm notfiers,
>>    the CPU PM common notifier is registering it in one place so that
>>    suspend is taken care.
>> - CPU COMPLEX events are renamed to more appropriate CPU CLUSTER.
>> - GIC distributor is not disabled to avoid the live locks. This is
>>    observed with CPUIDLE cases where at time CPU cluster fails to
>>    transition to low power states. As such there was no need to
>>    disable distributor in first place since on cluster reset, it
>>    will get disabled anyways.
>> - In VFP code, syscore ops are dropped in favour of CPU PM
>>    notifiers since S2R is already handled in core CPU PM notifiers.
>> - The last patch is an independent patch but can be pushed along with
>>    the other GIC changes done here.
>>
>> V1: [http://lwn.net/Articles/447259/]
>>
>> This patch set tries to address concerns with platform pm code
>> calling into the driver for every block in the Cortex A9s
>> during idle, hotplug, and suspend.  The first patch adds cpu pm
>> notifiers that can be called by platform code, the second uses
>> the notifier to save and restore the GIC state, and the third
>> saves the VFP state.
>>
>> The notifiers are used for two types of events, CPU PM events and
>> CPU cluster PM events.  CPU PM events are used to save and restore
>> per-cpu context when a single CPU is preparing to enter or has
>> just exited a low power state.  For example, the VFP saves the
>> last thread context, and the GIC saves banked CPU registers.
>>
>> CPU cluster events are used after all the CPUs in a power domain
>> have been prepared for the low power state.  The GIC uses these
>> events to save global register state.
>>
>> L2 cache is not covered by this patch set, as the determination
>> of when the L2 is reset and when it is retained is
>> platform-specific, and most of the APIs necessary are already
>>
>>
>> The series is tested with OMAP4 with S2R and CPUIDLE.
>>
>> The following changes since commit c6a389f123b9f68d605bb7e0f9b32ec1e3e14132:
>>
>>    Linux 3.1-rc4 (2011-08-28 21:16:01 -0700)
>>
>> Colin Cross (5):
>>        cpu_pm: Add cpu power management notifiers
>>        cpu_pm: call notifiers during suspend
>>        ARM: gic: Use cpu pm notifiers to save gic state
>>        ARM: vfp: Use cpu pm notifiers to save vfp state
>>        ARM: gic: Allow gic arch extensions to provide irqchip flags
>>
> Really appreciate the patches.  Now platform code needs to do nothing
> to have GIC back to work across suspend/resume cycle.
>
Yep.

> On i.MX6Q:
>
> Tested-and-Acked-by: Shawn Guo<shawn.guo@...aro.org>
>
Thanks for testing.

Regards
Santosh

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