| From 602bf40971d7f9a1ec0b7ba2b7e6427849828651 Mon Sep 17 00:00:00 2001 |
| From: Shawn Guo <shawn.guo@linaro.org> |
| Date: Tue, 22 May 2012 22:13:46 +0800 |
| Subject: ARM: imx6: exit coherency when shutting down a cpu |
| |
| From: Shawn Guo <shawn.guo@linaro.org> |
| |
| commit 602bf40971d7f9a1ec0b7ba2b7e6427849828651 upstream. |
| |
| There is a system hang issue on imx6q which can easily be seen with |
| running a cpu hotplug stress testing (hotplug secondary cores from |
| user space via sysfs interface for thousands iterations). |
| |
| It turns out that the issue is caused by coherency of the cpu that |
| is being shut down. When shutting down a cpu, we need to have the |
| cpu exit coherency to prevent it from receiving cache, TLB, or BTB |
| maintenance operations broadcast by other CPUs in the cluster. |
| |
| Copy cpu_enter_lowpower() and cpu_leave_lowpower() from mach-vexpress |
| to have coherency properly handled in platform_cpu_die(), thus fix |
| the issue. |
| |
| Signed-off-by: Shawn Guo <shawn.guo@linaro.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| arch/arm/mach-imx/hotplug.c | 42 +++++++++++++++++++++++++++++++++++++++++- |
| 1 file changed, 41 insertions(+), 1 deletion(-) |
| |
| --- a/arch/arm/mach-imx/hotplug.c |
| +++ b/arch/arm/mach-imx/hotplug.c |
| @@ -12,6 +12,7 @@ |
| |
| #include <linux/errno.h> |
| #include <asm/cacheflush.h> |
| +#include <asm/cp15.h> |
| #include <mach/common.h> |
| |
| int platform_cpu_kill(unsigned int cpu) |
| @@ -19,6 +20,44 @@ int platform_cpu_kill(unsigned int cpu) |
| return 1; |
| } |
| |
| +static inline void cpu_enter_lowpower(void) |
| +{ |
| + unsigned int v; |
| + |
| + flush_cache_all(); |
| + 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, %3\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), "Ir" (0x40) |
| + : "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, %2\n" |
| + " mcr p15, 0, %0, c1, c0, 1\n" |
| + : "=&r" (v) |
| + : "Ir" (CR_C), "Ir" (0x40) |
| + : "cc"); |
| +} |
| + |
| /* |
| * platform-specific code to shutdown a CPU |
| * |
| @@ -26,9 +65,10 @@ int platform_cpu_kill(unsigned int cpu) |
| */ |
| void platform_cpu_die(unsigned int cpu) |
| { |
| - flush_cache_all(); |
| + cpu_enter_lowpower(); |
| imx_enable_cpu(cpu, false); |
| cpu_do_idle(); |
| + cpu_leave_lowpower(); |
| |
| /* We should never return from idle */ |
| panic("cpu %d unexpectedly exit from shutdown\n", cpu); |