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authordavidwang <davidwang@zhaoxin.com>2018-01-22 18:14:17 +0800
committerThomas Gleixner <tglx@linutronix.de>2018-01-24 13:38:10 +0100
commitfe6daab1ee9dfe7f89974ee6c486cccb0f18a61d (patch)
tree7a8ad4a75e7aa384ae1011ed6abd7d6bd8d502b0 /arch
parentaa83c45762a242acce9b35020363225a7b59d7c9 (diff)
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 <davidwang@zhaoxin.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> 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
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/cpu/centaur.c4
1 files changed, 4 insertions, 0 deletions
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)