return ns;
}
-static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
+static void set_cyc2ns_scale(unsigned long khz, int cpu)
{
unsigned long long tsc_now, ns_now;
struct cyc2ns_data *data;
local_irq_save(flags);
sched_clock_idle_sleep_event();
- if (!cpu_khz)
+ if (!khz)
goto done;
data = cyc2ns_write_begin(cpu);
* time function is continuous; see the comment near struct
* cyc2ns_data.
*/
- clocks_calc_mult_shift(&data->cyc2ns_mul, &data->cyc2ns_shift, cpu_khz,
+ clocks_calc_mult_shift(&data->cyc2ns_mul, &data->cyc2ns_shift, khz,
NSEC_PER_MSEC, 0);
/*
}
/**
- * native_calibrate_tsc - calibrate the tsc on boot
+ * native_calibrate_tsc
+ * Determine TSC frequency via CPUID, else return 0.
*/
unsigned long native_calibrate_tsc(void)
{
+ unsigned int eax_denominator, ebx_numerator, ecx_hz, edx;
+ unsigned int crystal_khz;
+
+ if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
+ return 0;
+
+ if (boot_cpu_data.cpuid_level < 0x15)
+ return 0;
+
+ eax_denominator = ebx_numerator = ecx_hz = edx = 0;
+
+ /* CPUID 15H TSC/Crystal ratio, plus optionally Crystal Hz */
+ cpuid(0x15, &eax_denominator, &ebx_numerator, &ecx_hz, &edx);
+
+ if (ebx_numerator == 0 || eax_denominator == 0)
+ return 0;
+
+ crystal_khz = ecx_hz / 1000;
+
+ if (crystal_khz == 0) {
+ switch (boot_cpu_data.x86_model) {
+ case 0x4E: /* SKL */
+ case 0x5E: /* SKL */
+ crystal_khz = 24000; /* 24 MHz */
+ }
+ }
+
+ return crystal_khz * ebx_numerator / eax_denominator;
+}
+
+static unsigned long cpu_khz_from_cpuid(void)
+{
+ unsigned int eax_base_mhz, ebx_max_mhz, ecx_bus_mhz, edx;
+
+ if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
+ return 0;
+
+ if (boot_cpu_data.cpuid_level < 0x16)
+ return 0;
+
+ eax_base_mhz = ebx_max_mhz = ecx_bus_mhz = edx = 0;
+
+ cpuid(0x16, &eax_base_mhz, &ebx_max_mhz, &ecx_bus_mhz, &edx);
+
+ return eax_base_mhz * 1000;
+}
+
+/**
+ * native_calibrate_cpu - calibrate the cpu on boot
+ */
+unsigned long native_calibrate_cpu(void)
+{
u64 tsc1, tsc2, delta, ref1, ref2;
unsigned long tsc_pit_min = ULONG_MAX, tsc_ref_min = ULONG_MAX;
unsigned long flags, latch, ms, fast_calibrate;
int hpet = is_hpet_enabled(), i, loopmin;
+ fast_calibrate = cpu_khz_from_cpuid();
+ if (fast_calibrate)
+ return fast_calibrate;
+
fast_calibrate = cpu_khz_from_msr();
if (fast_calibrate)
return fast_calibrate;
if (!boot_cpu_has(X86_FEATURE_TSC))
return -ENODEV;
+ cpu_khz = x86_platform.calibrate_cpu();
tsc_khz = x86_platform.calibrate_tsc();
- cpu_khz = tsc_khz;
+ if (tsc_khz == 0)
+ tsc_khz = cpu_khz;
cpu_data(0).loops_per_jiffy = cpufreq_scale(cpu_data(0).loops_per_jiffy,
cpu_khz_old, cpu_khz);
return;
}
+ cpu_khz = x86_platform.calibrate_cpu();
tsc_khz = x86_platform.calibrate_tsc();
- cpu_khz = tsc_khz;
+ if (tsc_khz == 0)
+ tsc_khz = cpu_khz;
if (!tsc_khz) {
mark_tsc_unstable("could not calculate TSC khz");
*/
for_each_possible_cpu(cpu) {
cyc2ns_init(cpu);
- set_cyc2ns_scale(cpu_khz, cpu);
+ set_cyc2ns_scale(tsc_khz, cpu);
}
if (tsc_disabled > 0)