From: Bin Gao <bin....@intel.com> 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. Signed-off-by: Bin Gao <bin....@intel.com> [lenb: simplified] Signed-off-by: Len Brown <len.br...@intel.com> Signed-off-by: Yong, Jonathan <jonathan.y...@intel.com> --- arch/x86/kernel/tsc.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 75df3c0..5df7ae6 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -684,7 +684,11 @@ 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; } } @@ -882,8 +886,12 @@ int recalibrate_cpu_khz(void) if (cpu_has_tsc) { cpu_khz = x86_platform.calibrate_cpu(); 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); @@ -1298,8 +1306,16 @@ 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"); -- 2.7.3 -- _______________________________________________ linux-yocto mailing list linux-yocto@yoctoproject.org https://lists.yoctoproject.org/listinfo/linux-yocto