diff options
| author |   Len Brown <len.brown@intel.com> | 2016-06-17 01:22:52 -0400 |
|---|---|---|
| committer |   Ingo Molnar <mingo@kernel.org> | 2016-07-11 21:30:13 +0200 |
| commit | ff4c86635ee12461fd3bd911d7d5253394da8f9d (patch) | |
| tree | 46d410019a232f2b0ecc89375d68abcfc27f565e /arch/x86 | |
| parent | x86/tsc: Enumerate SKL cpu_khz and tsc_khz via CPUID (diff) | |
| download | linux-dev-ff4c86635ee12461fd3bd911d7d5253394da8f9d.tar.xz linux-dev-ff4c86635ee12461fd3bd911d7d5253394da8f9d.zip | |
x86/tsc: Enumerate BXT tsc_khz via CPUID
Hard code the BXT crystal clock (aka ART - Always Running Timer)
to 19.200 MHz, and use CPUID leaf 0x15 to determine the BXT TSC frequency.
Use tsc_khz to sanity check BXT cpu_khz,
which can be erroneous in some configurations.
(I simplified the original patch from Bin Gao.)
Original-From: Bin Gao <bin.gao@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/bf4e7c175acd6d09719c47c319b10ff1f0627ff8.1466138954.git.len.brown@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/kernel/tsc.c | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index e1496b79c28a..2a952fcb1516 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -693,7 +693,11 @@ unsigned long native_calibrate_tsc(void) switch (boot_cpu_data.x86_model) { case 0x4E: /* SKL */ case 0x5E: /* SKL */ - crystal_khz = 24000; /* 24 MHz */ + crystal_khz = 24000; /* 24.0 MHz */ + break; + case 0x5C: /* BXT */ + crystal_khz = 19200; /* 19.2 MHz */ + break; } } @@ -895,6 +899,8 @@ int recalibrate_cpu_khz(void) tsc_khz = x86_platform.calibrate_tsc(); if (tsc_khz == 0) tsc_khz = cpu_khz; + else if (abs(cpu_khz - tsc_khz) * 10 > tsc_khz) + cpu_khz = tsc_khz; cpu_data(0).loops_per_jiffy = cpufreq_scale(cpu_data(0).loops_per_jiffy, cpu_khz_old, cpu_khz); @@ -1302,8 +1308,16 @@ void __init tsc_init(void) cpu_khz = x86_platform.calibrate_cpu(); tsc_khz = x86_platform.calibrate_tsc(); + + /* + * Trust non-zero tsc_khz as authorative, + * and use it to sanity check cpu_khz, + * which will be off if system timer is off. + */ if (tsc_khz == 0) tsc_khz = cpu_khz; + else if (abs(cpu_khz - tsc_khz) * 10 > tsc_khz) + cpu_khz = tsc_khz; if (!tsc_khz) { mark_tsc_unstable("could not calculate TSC khz"); |