| Message ID | E1gXVI3-00088u-N6@rmk-PC.armlinux.org.uk (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | Clean up ARM SMP/CPU hotplug implementations | expand |
On 13/12/2018 19:00, Russell King wrote: > The CPU hotplug implementation on this platform is cargo-culted from > the plat-versatile implementation, and is buggy. Once a CPU hits the > "low power" loop, it will wait for pen_release to be set to the CPU > number to wake up again - but nothing in this implementation does that. > > So, once a CPU has entered cpu_die() it will never, ever leave. > > Remove this useless cargo-culted implementation. > > Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk> > --- > arch/arm/mach-oxnas/Makefile | 1 - > arch/arm/mach-oxnas/hotplug.c | 109 ------------------------------------------ > arch/arm/mach-oxnas/platsmp.c | 4 -- > 3 files changed, 114 deletions(-) > delete mode 100644 arch/arm/mach-oxnas/hotplug.c > > diff --git a/arch/arm/mach-oxnas/Makefile b/arch/arm/mach-oxnas/Makefile > index b625906a9970..61a34e1c0f22 100644 > --- a/arch/arm/mach-oxnas/Makefile > +++ b/arch/arm/mach-oxnas/Makefile > @@ -1,2 +1 @@ > obj-$(CONFIG_SMP) += platsmp.o headsmp.o > -obj-$(CONFIG_HOTPLUG_CPU) += hotplug.o > diff --git a/arch/arm/mach-oxnas/hotplug.c b/arch/arm/mach-oxnas/hotplug.c > deleted file mode 100644 > index 854f29b8cba6..000000000000 > --- a/arch/arm/mach-oxnas/hotplug.c > +++ /dev/null > @@ -1,109 +0,0 @@ > -/* > - * 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 <asm/cp15.h> > -#include <asm/smp_plat.h> > - > -static inline void cpu_enter_lowpower(void) > -{ > - unsigned int v; > - > - asm volatile( > - " mcr p15, 0, %1, c7, c5, 0\n" > - " mcr p15, 0, %1, c7, c10, 4\n" > - /* > - * Turn off coherency > - */ > - " mrc p15, 0, %0, c1, c0, 1\n" > - " bic %0, %0, #0x20\n" > - " mcr p15, 0, %0, c1, c0, 1\n" > - " mrc p15, 0, %0, c1, c0, 0\n" > - " bic %0, %0, %2\n" > - " mcr p15, 0, %0, c1, c0, 0\n" > - : "=&r" (v) > - : "r" (0), "Ir" (CR_C) > - : "cc"); > -} > - > -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, #0x20\n" > - " mcr p15, 0, %0, c1, c0, 1\n" > - : "=&r" (v) > - : "Ir" (CR_C) > - : "cc"); > -} > - > -static inline void platform_do_lowpower(unsigned int cpu, int *spurious) > -{ > - /* > - * there is no power-control hardware on this platform, so all > - * we can do is put the core into WFI; this is safe as the calling > - * code will have already disabled interrupts > - */ > - for (;;) { > - /* > - * here's the WFI > - */ > - asm(".word 0xe320f003\n" > - : > - : > - : "memory", "cc"); > - > - if (pen_release == cpu_logical_map(cpu)) { > - /* > - * 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 ox820_cpu_die(unsigned int cpu) > -{ > - int spurious = 0; > - > - /* > - * we're ready for shutdown now, so do it > - */ > - cpu_enter_lowpower(); > - 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-oxnas/platsmp.c b/arch/arm/mach-oxnas/platsmp.c > index 442cc8a2f7dc..735141c0e3a3 100644 > --- a/arch/arm/mach-oxnas/platsmp.c > +++ b/arch/arm/mach-oxnas/platsmp.c > @@ -19,7 +19,6 @@ > #include <asm/smp_scu.h> > > extern void ox820_secondary_startup(void); > -extern void ox820_cpu_die(unsigned int cpu); > > static void __iomem *cpu_ctrl; > static void __iomem *gic_cpu_ctrl; > @@ -94,9 +93,6 @@ static void __init ox820_smp_prepare_cpus(unsigned int max_cpus) > static const struct smp_operations ox820_smp_ops __initconst = { > .smp_prepare_cpus = ox820_smp_prepare_cpus, > .smp_boot_secondary = ox820_boot_secondary, > -#ifdef CONFIG_HOTPLUG_CPU > - .cpu_die = ox820_cpu_die, > -#endif > }; > > CPU_METHOD_OF_DECLARE(ox820_smp, "oxsemi,ox820-smp", &ox820_smp_ops); > Acked-by: Neil Armstrong <narmstrong@baylibre.com>
diff --git a/arch/arm/mach-oxnas/Makefile b/arch/arm/mach-oxnas/Makefile index b625906a9970..61a34e1c0f22 100644 --- a/arch/arm/mach-oxnas/Makefile +++ b/arch/arm/mach-oxnas/Makefile @@ -1,2 +1 @@ obj-$(CONFIG_SMP) += platsmp.o headsmp.o -obj-$(CONFIG_HOTPLUG_CPU) += hotplug.o diff --git a/arch/arm/mach-oxnas/hotplug.c b/arch/arm/mach-oxnas/hotplug.c deleted file mode 100644 index 854f29b8cba6..000000000000 --- a/arch/arm/mach-oxnas/hotplug.c +++ /dev/null @@ -1,109 +0,0 @@ -/* - * 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 <asm/cp15.h> -#include <asm/smp_plat.h> - -static inline void cpu_enter_lowpower(void) -{ - unsigned int v; - - asm volatile( - " mcr p15, 0, %1, c7, c5, 0\n" - " mcr p15, 0, %1, c7, c10, 4\n" - /* - * Turn off coherency - */ - " mrc p15, 0, %0, c1, c0, 1\n" - " bic %0, %0, #0x20\n" - " mcr p15, 0, %0, c1, c0, 1\n" - " mrc p15, 0, %0, c1, c0, 0\n" - " bic %0, %0, %2\n" - " mcr p15, 0, %0, c1, c0, 0\n" - : "=&r" (v) - : "r" (0), "Ir" (CR_C) - : "cc"); -} - -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, #0x20\n" - " mcr p15, 0, %0, c1, c0, 1\n" - : "=&r" (v) - : "Ir" (CR_C) - : "cc"); -} - -static inline void platform_do_lowpower(unsigned int cpu, int *spurious) -{ - /* - * there is no power-control hardware on this platform, so all - * we can do is put the core into WFI; this is safe as the calling - * code will have already disabled interrupts - */ - for (;;) { - /* - * here's the WFI - */ - asm(".word 0xe320f003\n" - : - : - : "memory", "cc"); - - if (pen_release == cpu_logical_map(cpu)) { - /* - * 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 ox820_cpu_die(unsigned int cpu) -{ - int spurious = 0; - - /* - * we're ready for shutdown now, so do it - */ - cpu_enter_lowpower(); - 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-oxnas/platsmp.c b/arch/arm/mach-oxnas/platsmp.c index 442cc8a2f7dc..735141c0e3a3 100644 --- a/arch/arm/mach-oxnas/platsmp.c +++ b/arch/arm/mach-oxnas/platsmp.c @@ -19,7 +19,6 @@ #include <asm/smp_scu.h> extern void ox820_secondary_startup(void); -extern void ox820_cpu_die(unsigned int cpu); static void __iomem *cpu_ctrl; static void __iomem *gic_cpu_ctrl; @@ -94,9 +93,6 @@ static void __init ox820_smp_prepare_cpus(unsigned int max_cpus) static const struct smp_operations ox820_smp_ops __initconst = { .smp_prepare_cpus = ox820_smp_prepare_cpus, .smp_boot_secondary = ox820_boot_secondary, -#ifdef CONFIG_HOTPLUG_CPU - .cpu_die = ox820_cpu_die, -#endif }; CPU_METHOD_OF_DECLARE(ox820_smp, "oxsemi,ox820-smp", &ox820_smp_ops);
The CPU hotplug implementation on this platform is cargo-culted from the plat-versatile implementation, and is buggy. Once a CPU hits the "low power" loop, it will wait for pen_release to be set to the CPU number to wake up again - but nothing in this implementation does that. So, once a CPU has entered cpu_die() it will never, ever leave. Remove this useless cargo-culted implementation. Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk> --- arch/arm/mach-oxnas/Makefile | 1 - arch/arm/mach-oxnas/hotplug.c | 109 ------------------------------------------ arch/arm/mach-oxnas/platsmp.c | 4 -- 3 files changed, 114 deletions(-) delete mode 100644 arch/arm/mach-oxnas/hotplug.c