Message-ID: <53E0EE32.7060500@linaro.org>
Date:	Tue, 05 Aug 2014 16:46:10 +0200
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Russell King <linux@....linux.org.uk>,
	Kukjin Kim <kgene.kim@...sung.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org
CC:	Kyungmin Park <kyungmin.park@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Tomasz Figa <t.figa@...sung.com>
Subject: Re: [PATCH v5 1/3] ARM: EXYNOS: Move code from hotplug.c to platsmp.c

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 ?

> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
> Reviewed-by: Tomasz Figa <t.figa@...sung.com>
>
> ---
> 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,
>


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