mirror of https://gitee.com/openkylin/linux.git
x86: use cpuid to check MWAIT support for C1
cpuid(0x05) provides extended information about MWAIT in EDX when bit 0 of ECX is set. Bit 4-7 of EDX determine whether MWAIT is supported for C1. C1E enabled CPUs have these bits set to 0. Based on an earlier patch from Andi Kleen. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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@ -122,19 +122,31 @@ static void poll_idle(void)
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*
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* idle=mwait overrides this decision and forces the usage of mwait.
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*/
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#define MWAIT_INFO 0x05
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#define MWAIT_ECX_EXTENDED_INFO 0x01
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#define MWAIT_EDX_C1 0xf0
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static int __cpuinit mwait_usable(const struct cpuinfo_x86 *c)
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{
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u32 eax, ebx, ecx, edx;
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if (force_mwait)
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return 1;
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if (c->x86_vendor == X86_VENDOR_AMD) {
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switch(c->x86) {
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case 0x10:
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case 0x11:
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if (c->cpuid_level < MWAIT_INFO)
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return 0;
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}
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}
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cpuid(MWAIT_INFO, &eax, &ebx, &ecx, &edx);
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/* Check, whether EDX has extended info about MWAIT */
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if (!(ecx & MWAIT_ECX_EXTENDED_INFO))
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return 1;
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/*
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* edx enumeratios MONITOR/MWAIT extensions. Check, whether
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* C1 supports MWAIT
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*/
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return (edx & MWAIT_EDX_C1);
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}
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void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c)
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