linux-kernel - Re: [PATCH v3 3/3] arm: kernel: implement cpuidle

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Date:	Tue, 14 Jul 2015 12:03:02 +0100
From:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Jisheng Zhang <jszhang@...vell.com>,
	Will Deacon <Will.Deacon@....com>,
	Mark Rutland <Mark.Rutland@....com>,
	"daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"galak@...eaurora.org" <galak@...eaurora.org>,
	"agross@...eaurora.org" <agross@...eaurora.org>,
	"davidb@...eaurora.org" <davidb@...eaurora.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 3/3] arm: kernel: implement cpuidle_ops with psci
 backend

On Tue, Jul 14, 2015 at 11:34:21AM +0100, Russell King - ARM Linux wrote:
> On Thu, Jul 09, 2015 at 04:31:25PM +0800, Jisheng Zhang wrote:
> > This patch implements cpuidle_ops using psci. After this patch, we can
> > use cpuidle-arm.c with psci backend for both arm and arm64.
> > 
> > Signed-off-by: Jisheng Zhang <jszhang@...vell.com>
> > ---
> >  arch/arm/kernel/Makefile       |  1 +
> >  arch/arm/kernel/psci_cpuidle.c | 19 +++++++++++++++++++
> >  2 files changed, 20 insertions(+)
> >  create mode 100644 arch/arm/kernel/psci_cpuidle.c
> > 
> > diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
> > index 3b995f5..96383d8 100644
> > --- a/arch/arm/kernel/Makefile
> > +++ b/arch/arm/kernel/Makefile
> > @@ -91,6 +91,7 @@ obj-$(CONFIG_ARM_VIRT_EXT)	+= hyp-stub.o
> >  ifeq ($(CONFIG_ARM_PSCI),y)
> >  obj-y				+= psci-call.o
> >  obj-$(CONFIG_SMP)		+= psci_smp.o
> > +obj-$(CONFIG_CPU_IDLE)		+= psci_cpuidle.o
> >  endif
> >  
> >  extra-y := $(head-y) vmlinux.lds
> > diff --git a/arch/arm/kernel/psci_cpuidle.c b/arch/arm/kernel/psci_cpuidle.c
> > new file mode 100644
> > index 0000000..e7146d2
> > --- /dev/null
> > +++ b/arch/arm/kernel/psci_cpuidle.c
> > @@ -0,0 +1,19 @@
> > +/*
> > + * Copyright (C) 2015 Marvell Technology Group Ltd.
> > + * Author: Jisheng Zhang <jszhang@...vell.com>
> > + *
> > + * This program is free software; you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License version 2 as
> > + * published by the Free Software Foundation.
> > + */
> > +
> > +#include <linux/cpuidle.h>
> > +#include <linux/psci.h>
> > +
> > +#include <asm/cpuidle.h>
> > +
> > +static struct cpuidle_ops psci_cpuidle_ops __initdata = {
> > +	.suspend = cpu_psci_cpu_suspend,
> > +	.init = cpu_psci_cpu_init_idle,
> > +};
> > +CPUIDLE_METHOD_OF_DECLARE(psci_cpuidle, "psci", &psci_cpuidle_ops);
> 
> Is there any reason this can't live in the drivers sub-tree?  Is there
> anything specific to 32-bit ARM about this?
> 
> It looks to me like the right thing to do is to have it as part of
> drivers/firmware/psci.c.

I take this as an ACK to M.Rutland's PSCI code move to drivers/firmware,
right ?

http://lists.infradead.org/pipermail/linux-arm-kernel/2015-July/355643.html

> We don't do this for other stuff - we don't have IRQ_CHIP_OF_DECLARE
> stuff in arch/arm but have the IRQ chip drivers in drivers/irqchip.
> We keep it all togehter in drivers/irqchip, even when the IRQ chip
> driver is only useful on ARM.

CPUidle operations are ARM only, they are not used on ARM64, so
they belong in arch/arm (that's the same thing as SMP ops, on ARM64
SMP ops and CPUidle ops are unified through CPU operations).

Thanks,
Lorenzo
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