Subject: [PATCH v5 1/3] ARM: EXYNOS: Move code from hotplug.c to platsmp.c

From: [email-masked] (Krzysztof Kozlowski)
Date: Tue, 05 Aug 2014 17:03:26 +0200

On wto, 2014-08-05 at 16:46 +0200, Daniel Lezcano wrote:
> On 08/05/2014 12:43 PM, Krzysztof Kozlowski wrote:
> > Cleanup a little the SMP/hotplug code for Exynos by:
> > 1. Moving completely all functions from hotplug.c into the platsmp.c;
> > 2. Deleting the hotplug.c file.
> >
> > After recent cleanups (e.g. 75ad2ab28f0f "ARM: EXYNOS: use
> > v7_exit_coherency_flush macro for cache disabling") there was only CPU
> > power down related code in hotplug.c file. Keeping this file does not
> > give any benefits.
> >
> > The commit only moves code around with one additional observable change:
> > the hotplug.c was compiled with custom CFLAGS (-march=armv7-a). These
> > CFLAGS are not necessary any more.
> 
> What is the benefit of moving this code around ?
> 
> Usually the cpu hotplug code is located in hotplug.c for most of the 
> platforms, so why moving pm code inside platsmp ?

The benefits are:

1. Less dependencies, cleaner code because platsmp.c is the only user of
code located in hotplug.c. So the exynos_cpu_die() had to be declared in
common.h.

2. Less dependencies between modules after adding patch 3/3 [1] which
introduces exynos_set_delayed_reset_assertion() function. The
exynos_set_delayed_reset_assertion() is called by:
 - cpu_leave_power (hotplug.c)
 - platform_do_lowpower (hotplug.c)
 - exynos_boot_secondary (platsmp.c)

so merging everything into one file seemed simpler and cleaner.

However I do not insist on such solution. I'm merely interested in
getting the third patch into the kernel :) .

[1] http://www.spinics.net/lists/arm-kernel/msg352890.html

Best regards,
Krzysztof

> 
> > Signed-off-by: Krzysztof Kozlowski <[email-masked]>
> > Reviewed-by: Tomasz Figa <[email-masked]>
> >
> > ---
> > Changes since v4:
> > 1. Rebase on linux-next-20140804.
> > 2. Add Reviewed-by Tomasz Figa.
> > ---
> >   arch/arm/mach-exynos/Makefile  |  3 --
> >   arch/arm/mach-exynos/common.h  |  2 -
> >   arch/arm/mach-exynos/hotplug.c | 91 ------------------------------------------
> >   arch/arm/mach-exynos/platsmp.c | 74 ++++++++++++++++++++++++++++++++++
> >   4 files changed, 74 insertions(+), 96 deletions(-)
> >   delete mode 100644 arch/arm/mach-exynos/hotplug.c
> >
> > diff --git a/arch/arm/mach-exynos/Makefile b/arch/arm/mach-exynos/Makefile
> > index 788f26d21141..0095de99d703 100644
> > --- a/arch/arm/mach-exynos/Makefile
> > +++ b/arch/arm/mach-exynos/Makefile
> > @@ -21,9 +21,6 @@ obj-$(CONFIG_PM_GENERIC_DOMAINS) += pm_domains.o
> >
> >   obj-$(CONFIG_SMP)		+= platsmp.o headsmp.o
> >
> > -obj-$(CONFIG_HOTPLUG_CPU)	+= hotplug.o
> > -CFLAGS_hotplug.o		+= -march=armv7-a
> > -
> >   plus_sec := $(call as-instr,.arch_extension sec,+sec)
> >   AFLAGS_exynos-smc.o		:=-Wa,-march=armv7-a$(plus_sec)
> >
> > diff --git a/arch/arm/mach-exynos/common.h b/arch/arm/mach-exynos/common.h
> > index 47b904b3b973..3d3e6af9d015 100644
> > --- a/arch/arm/mach-exynos/common.h
> > +++ b/arch/arm/mach-exynos/common.h
> > @@ -130,8 +130,6 @@ extern void exynos_cpu_resume(void);
> >
> >   extern struct smp_operations exynos_smp_ops;
> >
> > -extern void exynos_cpu_die(unsigned int cpu);
> > -
> >   /* PMU(Power Management Unit) support */
> >
> >   #define PMU_TABLE_END	(-1U)
> > diff --git a/arch/arm/mach-exynos/hotplug.c b/arch/arm/mach-exynos/hotplug.c
> > deleted file mode 100644
> > index 4d86961a7957..000000000000
> > --- a/arch/arm/mach-exynos/hotplug.c
> > +++ /dev/null
> > @@ -1,91 +0,0 @@
> > -/*
> > - *  Cloned from linux/arch/arm/mach-realview/hotplug.c
> > - *
> > - *  Copyright (C) 2002 ARM Ltd.
> > - *  All Rights Reserved
> > - *
> > - * 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/kernel.h>
> > -#include <linux/errno.h>
> > -#include <linux/smp.h>
> > -#include <linux/io.h>
> > -
> > -#include <asm/cacheflush.h>
> > -#include <asm/cp15.h>
> > -#include <asm/smp_plat.h>
> > -
> > -#include "common.h"
> > -#include "regs-pmu.h"
> > -
> > -static inline void cpu_leave_lowpower(void)
> > -{
> > -	unsigned int v;
> > -
> > -	asm volatile(
> > -	"mrc	p15, 0, %0, c1, c0, 0\n"
> > -	"	orr	%0, %0, %1\n"
> > -	"	mcr	p15, 0, %0, c1, c0, 0\n"
> > -	"	mrc	p15, 0, %0, c1, c0, 1\n"
> > -	"	orr	%0, %0, %2\n"
> > -	"	mcr	p15, 0, %0, c1, c0, 1\n"
> > -	  : "=&r" (v)
> > -	  : "Ir" (CR_C), "Ir" (0x40)
> > -	  : "cc");
> > -}
> > -
> > -static inline void platform_do_lowpower(unsigned int cpu, int *spurious)
> > -{
> > -	u32 mpidr = cpu_logical_map(cpu);
> > -	u32 core_id = MPIDR_AFFINITY_LEVEL(mpidr, 0);
> > -
> > -	for (;;) {
> > -
> > -		/* Turn the CPU off on next WFI instruction. */
> > -		exynos_cpu_power_down(core_id);
> > -
> > -		wfi();
> > -
> > -		if (pen_release == core_id) {
> > -			/*
> > -			 * OK, proper wakeup, we're done
> > -			 */
> > -			break;
> > -		}
> > -
> > -		/*
> > -		 * Getting here, means that we have come out of WFI without
> > -		 * having been woken up - this shouldn't happen
> > -		 *
> > -		 * Just note it happening - when we're woken, we can report
> > -		 * its occurrence.
> > -		 */
> > -		(*spurious)++;
> > -	}
> > -}
> > -
> > -/*
> > - * platform-specific code to shutdown a CPU
> > - *
> > - * Called with IRQs disabled
> > - */
> > -void __ref exynos_cpu_die(unsigned int cpu)
> > -{
> > -	int spurious = 0;
> > -
> > -	v7_exit_coherency_flush(louis);
> > -
> > -	platform_do_lowpower(cpu, &spurious);
> > -
> > -	/*
> > -	 * bring this CPU back into the world of cache
> > -	 * coherency, and then restore interrupts
> > -	 */
> > -	cpu_leave_lowpower();
> > -
> > -	if (spurious)
> > -		pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious);
> > -}
> > diff --git a/arch/arm/mach-exynos/platsmp.c b/arch/arm/mach-exynos/platsmp.c
> > index a9f1cf759949..a809f76c8160 100644
> > --- a/arch/arm/mach-exynos/platsmp.c
> > +++ b/arch/arm/mach-exynos/platsmp.c
> > @@ -22,6 +22,7 @@
> >   #include <linux/of_address.h>
> >
> >   #include <asm/cacheflush.h>
> > +#include <asm/cp15.h>
> >   #include <asm/smp_plat.h>
> >   #include <asm/smp_scu.h>
> >   #include <asm/firmware.h>
> > @@ -33,6 +34,54 @@
> >
> >   extern void exynos4_secondary_startup(void);
> >
> > +#ifdef CONFIG_HOTPLUG_CPU
> > +static inline void cpu_leave_lowpower(void)
> > +{
> > +	unsigned int v;
> > +
> > +	asm volatile(
> > +	"mrc	p15, 0, %0, c1, c0, 0\n"
> > +	"	orr	%0, %0, %1\n"
> > +	"	mcr	p15, 0, %0, c1, c0, 0\n"
> > +	"	mrc	p15, 0, %0, c1, c0, 1\n"
> > +	"	orr	%0, %0, %2\n"
> > +	"	mcr	p15, 0, %0, c1, c0, 1\n"
> > +	  : "=&r" (v)
> > +	  : "Ir" (CR_C), "Ir" (0x40)
> > +	  : "cc");
> > +}
> > +
> > +static inline void platform_do_lowpower(unsigned int cpu, int *spurious)
> > +{
> > +	u32 mpidr = cpu_logical_map(cpu);
> > +	u32 core_id = MPIDR_AFFINITY_LEVEL(mpidr, 0);
> > +
> > +	for (;;) {
> > +
> > +		/* Turn the CPU off on next WFI instruction. */
> > +		exynos_cpu_power_down(core_id);
> > +
> > +		wfi();
> > +
> > +		if (pen_release == core_id) {
> > +			/*
> > +			 * OK, proper wakeup, we're done
> > +			 */
> > +			break;
> > +		}
> > +
> > +		/*
> > +		 * Getting here, means that we have come out of WFI without
> > +		 * having been woken up - this shouldn't happen
> > +		 *
> > +		 * Just note it happening - when we're woken, we can report
> > +		 * its occurrence.
> > +		 */
> > +		(*spurious)++;
> > +	}
> > +}
> > +#endif /* CONFIG_HOTPLUG_CPU */
> > +
> >   /**
> >    * exynos_core_power_down : power down the specified cpu
> >    * @cpu : the cpu to power down
> > @@ -318,6 +367,31 @@ static void __init exynos_smp_prepare_cpus(unsigned int max_cpus)
> >   	}
> >   }
> >
> > +#ifdef CONFIG_HOTPLUG_CPU
> > +/*
> > + * platform-specific code to shutdown a CPU
> > + *
> > + * Called with IRQs disabled
> > + */
> > +static void __ref exynos_cpu_die(unsigned int cpu)
> > +{
> > +	int spurious = 0;
> > +
> > +	v7_exit_coherency_flush(louis);
> > +
> > +	platform_do_lowpower(cpu, &spurious);
> > +
> > +	/*
> > +	 * bring this CPU back into the world of cache
> > +	 * coherency, and then restore interrupts
> > +	 */
> > +	cpu_leave_lowpower();
> > +
> > +	if (spurious)
> > +		pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious);
> > +}
> > +#endif /* CONFIG_HOTPLUG_CPU */
> > +
> >   struct smp_operations exynos_smp_ops __initdata = {
> >   	.smp_init_cpus		= exynos_smp_init_cpus,
> >   	.smp_prepare_cpus	= exynos_smp_prepare_cpus,
> >
> 
>