From fe6daab1ee9dfe7f89974ee6c486cccb0f18a61d Mon Sep 17 00:00:00 2001 From: davidwang Date: Mon, 22 Jan 2018 18:14:17 +0800 Subject: x86/centaur: Mark TSC invariant Centaur CPU has a constant frequency TSC and that TSC does not stop in C-States. But because the corresponding TSC feature flags are not set for that CPU, the TSC is treated as not constant frequency and assumed to stop in C-States, which makes it an unreliable and unusable clock source. Setting those flags tells the kernel that the TSC is usable, so it will select it over HPET. The effect of this is that reading time stamps (from kernel or user space) will be faster and more efficent. Signed-off-by: davidwang Signed-off-by: Thomas Gleixner Cc: qiyuanwang@zhaoxin.com Cc: linux-pm@vger.kernel.org Cc: brucechang@via-alliance.com Cc: cooperyan@zhaoxin.com Cc: benjaminpan@viatech.com Link: https://lkml.kernel.org/r/1516616057-5158-1-git-send-email-davidwang@zhaoxin.com --- arch/x86/kernel/cpu/centaur.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'arch/x86/kernel/cpu') diff --git a/arch/x86/kernel/cpu/centaur.c b/arch/x86/kernel/cpu/centaur.c index 68bc6d9b3132..c578cd29c2d2 100644 --- a/arch/x86/kernel/cpu/centaur.c +++ b/arch/x86/kernel/cpu/centaur.c @@ -106,6 +106,10 @@ static void early_init_centaur(struct cpuinfo_x86 *c) #ifdef CONFIG_X86_64 set_cpu_cap(c, X86_FEATURE_SYSENTER32); #endif + if (c->x86_power & (1 << 8)) { + set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC); + set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC); + } } static void init_centaur(struct cpuinfo_x86 *c) -- cgit