Newer processors implement cpuid extension to determine CPU frequency
from cpuid. This patch adds a function that can do this early in boot.
Signed-off-by: Pavel Tatashin <pasha.tatas...@oracle.com>
---
arch/x86/kernel/tsc.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 1c9fc23..58bd575 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -743,14 +743,14 @@ unsigned long native_calibrate_tsc(void)
return tsc_khz;
}
-static unsigned long cpu_khz_from_cpuid(void)
+static unsigned long cpu_khz_from_cpuid_early(int vendor, int cpuid_level)
{
unsigned int eax_base_mhz, ebx_max_mhz, ecx_bus_mhz, edx;
- if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
+ if (vendor != X86_VENDOR_INTEL)
return 0;
- if (boot_cpu_data.cpuid_level < 0x16)
+ if (cpuid_level < 0x16)
return 0;
eax_base_mhz = ebx_max_mhz = ecx_bus_mhz = edx = 0;
@@ -770,7 +770,9 @@ unsigned long native_calibrate_cpu(void)
unsigned long flags, latch, ms, fast_calibrate;
int hpet = is_hpet_enabled(), i, loopmin;
- fast_calibrate = cpu_khz_from_cpuid();
+ fast_calibrate = cpu_khz_from_cpuid_early(boot_cpu_data.x86_vendor,
+ boot_cpu_data.cpuid_level);
+
if (fast_calibrate)
return fast_calibrate;
--
1.8.3.1
