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

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Message-ID: <20110906023430.GA7651@S2100-06.ap.freescale.net>
Date:	Tue, 6 Sep 2011 10:34:32 +0800
From:	Shawn Guo <shawn.guo@...escale.com>
To:	Santosh Shilimkar <santosh.shilimkar@...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 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.

On i.MX6Q:

Tested-and-Acked-by: Shawn Guo <shawn.guo@...aro.org>

-- 
Regards,
Shawn

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