diff options
Diffstat (limited to 'arch/x86/kernel/process.c')
| -rw-r--r-- | arch/x86/kernel/process.c | 36 |
1 files changed, 27 insertions, 9 deletions
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 67e9b4a1e89d..ba370dc8685b 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -99,15 +99,6 @@ static void mwait_idle(void) local_irq_enable(); } - -static int __cpuinit mwait_usable(const struct cpuinfo_x86 *c) -{ - if (force_mwait) - return 1; - /* Any C1 states supported? */ - return c->cpuid_level >= 5 && ((cpuid_edx(5) >> 4) & 0xf) > 0; -} - /* * On SMP it's slightly faster (but much more power-consuming!) * to poll the ->work.need_resched flag instead of waiting for the @@ -119,6 +110,33 @@ static void poll_idle(void) cpu_relax(); } +/* + * mwait selection logic: + * + * It depends on the CPU. For AMD CPUs that support MWAIT this is + * wrong. Family 0x10 and 0x11 CPUs will enter C1 on HLT. Powersavings + * then depend on a clock divisor and current Pstate of the core. If + * all cores of a processor are in halt state (C1) the processor can + * enter the C1E (C1 enhanced) state. If mwait is used this will never + * happen. + * + * idle=mwait overrides this decision and forces the usage of mwait. + */ +static int __cpuinit mwait_usable(const struct cpuinfo_x86 *c) +{ + if (force_mwait) + return 1; + + if (c->x86_vendor == X86_VENDOR_AMD) { + switch(c->x86) { + case 0x10: + case 0x11: + return 0; + } + } + return 1; +} + void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c) { static int selected; |