From mboxrd@z Thu Jan  1 00:00:00 1970
From: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Subject: Re: [PATCH v3 2/2] ARM64: kernel: PSCI: move PSCI idle management
 code to drivers/firmware
Date: Tue, 5 Jan 2016 12:31:34 +0000
Message-ID: <20160105123134.GA1821@red-moon>
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To: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: linux-arm-kernel@lists.infradead.org, linux-pm@vger.kernel.org, Will Deacon <will.deacon@arm.com>, Sudeep Holla <sudeep.holla@arm.com>, Daniel Lezcano <daniel.lezcano@linaro.org>, Catalin Marinas <catalin.marinas@arm.com>, Mark Rutland <mark.rutland@arm.com>, Jisheng Zhang <jszhang@marvell.com>

On Tue, Jan 05, 2016 at 10:59:01AM +0000, Russell King - ARM Linux wrote:
> On Fri, Oct 16, 2015 at 05:02:59PM +0100, Lorenzo Pieralisi wrote:
> > ARM64 PSCI kernel interfaces that initialize idle states and implement
> > the suspend API to enter them are generic and can be shared with the
> > ARM architecture.
> > 
> > To achieve that goal, this patch moves ARM64 PSCI idle management
> > code to drivers/firmware, so that the interface to initialize and
> > enter idle states can actually be shared by ARM and ARM64 arches
> > back-ends.
> > 
> > The ARM generic CPUidle implementation also requires the definition of
> > a cpuidle_ops section entry for the kernel to initialize the CPUidle
> > operations at boot based on the enable-method (ie ARM64 has the
> > statically initialized cpu_ops counterparts for that purpose); therefore
> > this patch also adds the required section entry on CONFIG_ARM for PSCI so
> > that the kernel can initialize the PSCI CPUidle back-end when PSCI is
> > the probed enable-method.
> > 
> > On ARM64 this patch provides no functional change.
> 
> On ARM64, it causes build breakage though:
> 
> drivers/built-in.o: In function `psci_suspend_finisher':
> arm_pmu.c:(.text+0xc6494): undefined reference to `cpu_resume'
> arm_pmu.c:(.text+0xc6498): undefined reference to `cpu_resume'
> drivers/built-in.o: In function `psci_cpu_suspend_enter':
> arm_pmu.c:(.text+0xc66c0): undefined reference to `cpu_suspend'
> 
> The code which has been moved looks similar.  However, when it lived
> in arch/arm64/kernel/psci.c, it was protected by
> #ifdef CONFIG_HOTPLUG_CPU.  In its new location, there are no ifdefs
> around it, and so if it gets built without CONFIG_ARM_CPU_SUSPEND on
> ARM, or CONFIG_CPU_PM for ARM64, it will error out like the above.
> 
> As this is causing a regression, and I've now closed my tree, I will
> be doing what I said yesterday: I'll be dropping this patch for this
> merge window in order to stabilise my tree.  Sorry.

My bad, I apologise, I will likely have to add a config option to
make sure cpu_{suspend/resume} code is compiled in (on both ARM/ARM64),
thanks for spotting it.

Lorenzo