From: Len Brown <len.br...@intel.com> tsc_msr is used to quickly and reliably enumerate the CPU/TSC frequencies at boot time For the Intel Atom Architecture.
Extend tsc_msr to include recent Intel Core Architecture. As this code discovers BCLK, it also sets lapic_timer_frequency, which allows LAPIC timer calibration to be skipped, though it is already skipped on systems with a TSC deadline timer. Signed-off-by: Len Brown <len.br...@intel.com> --- arch/x86/kernel/tsc_msr.c | 49 +++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 41 insertions(+), 8 deletions(-) diff --git a/arch/x86/kernel/tsc_msr.c b/arch/x86/kernel/tsc_msr.c index 65b3d8cb..9d56ebd 100644 --- a/arch/x86/kernel/tsc_msr.c +++ b/arch/x86/kernel/tsc_msr.c @@ -77,23 +77,56 @@ unsigned long try_msr_calibrate_tsc(void) if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) return 0; + /* + * 100 MHz BCLK Core Architecture -- before SKL. + * De-rate 100Mhz by about 0.25% to account + * for the average effect of spread-spectrum clocking. + */ + switch (boot_cpu_data.x86_model) { + + case 0x2A: /* SNB */ + case 0x3A: /* IVB */ + freq = 99773; + goto get_ratio; + case 0x2D: /* SNB Xeon */ + case 0x3E: /* IVB Xeon */ + freq = 99760; + goto get_ratio; + case 0x3C: /* HSW */ + case 0x3F: /* HSW */ + case 0x45: /* HSW */ + case 0x46: /* HSW */ + case 0x3D: /* BDW */ + case 0x47: /* BDW */ + case 0x4F: /* BDX */ + case 0x56: /* BDX-DE */ + freq = 99769; + goto get_ratio; + } + + /* + * Atom Architecture + */ cpu_index = match_cpu(boot_cpu_data.x86, boot_cpu_data.x86_model); if (cpu_index < 0) return 0; - if (freq_desc_tables[cpu_index].msr_plat) { - rdmsr(MSR_PLATFORM_INFO, lo, hi); - ratio = (lo >> 8) & 0xff; - } else { - rdmsr(MSR_IA32_PERF_STATUS, lo, hi); - ratio = (hi >> 8) & 0x1f; - } - /* Get FSB FREQ ID */ rdmsr(MSR_FSB_FREQ, lo, hi); freq_id = lo & 0x7; freq = id_to_freq(cpu_index, freq_id); + if (!freq_desc_tables[cpu_index].msr_plat) { + rdmsr(MSR_IA32_PERF_STATUS, lo, hi); + ratio = (hi >> 8) & 0x1f; + goto done; + } + +get_ratio: + rdmsr(MSR_PLATFORM_INFO, lo, hi); + ratio = (lo >> 8) & 0xff; + +done: /* TSC frequency = maximum resolved freq * maximum resolved bus ratio */ res = freq * ratio; -- 2.9.0