4 files changed, 73 insertions, 8 deletions

diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h
index db1f779a3766..a30591e1567c 100644
--- a/arch/x86/include/asm/tsc.h
+++ b/arch/x86/include/asm/tsc.h
@@ -36,6 +36,7 @@ extern void mark_tsc_unstable(char *reason);
 extern int unsynchronized_tsc(void);
 extern int check_tsc_unstable(void);
 extern int check_tsc_disabled(void);
+extern unsigned long native_calibrate_cpu(void);
 extern unsigned long native_calibrate_tsc(void);
 extern unsigned long long native_sched_clock_from_tsc(u64 tsc);
 
diff --git a/arch/x86/include/asm/x86_init.h b/arch/x86/include/asm/x86_init.h
index 4dcdf74dfed8..08a08a800e17 100644
--- a/arch/x86/include/asm/x86_init.h
+++ b/arch/x86/include/asm/x86_init.h
@@ -181,7 +181,8 @@ struct x86_legacy_features {
 
 /**
  * struct x86_platform_ops - platform specific runtime functions
- * @calibrate_tsc:		calibrate TSC
+ * @calibrate_cpu:		calibrate CPU
+ * @calibrate_tsc:		calibrate TSC, if different from CPU
  * @get_wallclock:		get time from HW clock like RTC etc.
  * @set_wallclock:		set time back to HW clock
  * @is_untracked_pat_range	exclude from PAT logic
@@ -200,6 +201,7 @@ struct x86_legacy_features {
  * 				semantics.
  */
 struct x86_platform_ops {
+	unsigned long (*calibrate_cpu)(void);
 	unsigned long (*calibrate_tsc)(void);
 	void (*get_wallclock)(struct timespec *ts);
 	int (*set_wallclock)(const struct timespec *ts);
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 35a3976c19cc..e1496b79c28a 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -239,7 +239,7 @@ static inline unsigned long long cycles_2_ns(unsigned long long cyc)
 	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;
@@ -248,7 +248,7 @@ static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
 	local_irq_save(flags);
 	sched_clock_idle_sleep_event();
 
-	if (!cpu_khz)
+	if (!khz)
 		goto done;
 
 	data = cyc2ns_write_begin(cpu);
@@ -261,7 +261,7 @@ static void set_cyc2ns_scale(unsigned long cpu_khz, int 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);
 
 	/*
@@ -665,15 +665,72 @@ success:
 }
 
 /**
- * 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;
@@ -834,8 +891,10 @@ int recalibrate_cpu_khz(void)
 	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);
 
@@ -1241,8 +1300,10 @@ void __init tsc_init(void)
 		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");
@@ -1262,7 +1323,7 @@ void __init tsc_init(void)
 	 */
 	for_each_possible_cpu(cpu) {
 		cyc2ns_init(cpu);
-		set_cyc2ns_scale(cpu_khz, cpu);
+		set_cyc2ns_scale(tsc_khz, cpu);
 	}
 
 	if (tsc_disabled > 0)
diff --git a/arch/x86/kernel/x86_init.c b/arch/x86/kernel/x86_init.c
index dad5fe9633a3..58b459296e13 100644
--- a/arch/x86/kernel/x86_init.c
+++ b/arch/x86/kernel/x86_init.c
@@ -92,6 +92,7 @@ static void default_nmi_init(void) { };
 static int default_i8042_detect(void) { return 1; };
 
 struct x86_platform_ops x86_platform = {
+	.calibrate_cpu			= native_calibrate_cpu,
 	.calibrate_tsc			= native_calibrate_tsc,
 	.get_wallclock			= mach_get_cmos_time,
 	.set_wallclock			= mach_set_rtc_mmss,