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Message-id: <1407251006.9849.8.camel@AMDC1943>
Date: Tue, 05 Aug 2014 17:03:26 +0200
From: Krzysztof Kozlowski <k.kozlowski@...sung.com>
To: Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: 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,
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 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 <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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