Commit-ID: 47c95a46d0fae07762f0a38aa3709ae63f307048 Gitweb: http://git.kernel.org/tip/47c95a46d0fae07762f0a38aa3709ae63f307048 Author: Bin Gao <bin....@linux.intel.com> AuthorDate: Tue, 15 Nov 2016 12:27:21 -0800 Committer: Thomas Gleixner <t...@linutronix.de> CommitDate: Fri, 18 Nov 2016 10:58:30 +0100
x86/tsc: Add X86_FEATURE_TSC_KNOWN_FREQ flag The X86_FEATURE_TSC_RELIABLE flag in Linux kernel implies both reliable (at runtime) and trustable (at calibration). But reliable running and trustable calibration independent of each other. Add a new flag X86_FEATURE_TSC_KNOWN_FREQ, which denotes that the frequency is known (via MSR/CPUID). This flag is only meant to skip the long term calibration on systems which have a known frequency. Add X86_FEATURE_TSC_KNOWN_FREQ to the skip the delayed calibration and leave X86_FEATURE_TSC_RELIABLE in place. After converting the existing users of X86_FEATURE_TSC_RELIABLE to use either both flags or just X86_FEATURE_TSC_KNOWN_FREQ we can seperate the functionality. Suggested-by: Thomas Gleixner <t...@linutronix.de> Signed-off-by: Bin Gao <bin....@intel.com> Cc: Peter Zijlstra <pet...@infradead.org> Link: http://lkml.kernel.org/r/1479241644-234277-2-git-send-email-bin....@linux.intel.com Signed-off-by: Thomas Gleixner <t...@linutronix.de> --- arch/x86/include/asm/cpufeatures.h | 1 + arch/x86/kernel/tsc.c | 11 ++++++++--- 2 files changed, 9 insertions(+), 3 deletions(-) diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index a396292..7f6a5f8 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -106,6 +106,7 @@ #define X86_FEATURE_APERFMPERF ( 3*32+28) /* APERFMPERF */ #define X86_FEATURE_EAGER_FPU ( 3*32+29) /* "eagerfpu" Non lazy FPU restore */ #define X86_FEATURE_NONSTOP_TSC_S3 ( 3*32+30) /* TSC doesn't stop in S3 state */ +#define X86_FEATURE_TSC_KNOWN_FREQ ( 3*32+31) /* TSC has known frequency */ /* Intel-defined CPU features, CPUID level 0x00000001 (ecx), word 4 */ #define X86_FEATURE_XMM3 ( 4*32+ 0) /* "pni" SSE-3 */ diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 46b2f41..d2c4ee4 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -1283,10 +1283,15 @@ static int __init init_tsc_clocksource(void) clocksource_tsc.flags |= CLOCK_SOURCE_SUSPEND_NONSTOP; /* - * Trust the results of the earlier calibration on systems - * exporting a reliable TSC. + * When TSC frequency is known (retrieved via MSR or CPUID), we skip + * the refined calibration and directly register it as a clocksource. + * + * We still keep the TSC_RELIABLE flag here to avoid regressions - + * it will be removed after all the conversion for other code paths + * connected to this flag is done. */ - if (boot_cpu_has(X86_FEATURE_TSC_RELIABLE)) { + if (boot_cpu_has(X86_FEATURE_TSC_RELIABLE) || + boot_cpu_has(X86_FEATURE_TSC_KNOWN_FREQ)) { clocksource_register_khz(&clocksource_tsc, tsc_khz); return 0; }
