Author: kib
Date: Wed May 2 07:42:47 2018
New Revision: 333161
URL: https://svnweb.freebsd.org/changeset/base/333161
Log:
MFC r333002:
Use CPUID leaf 0x15 to get TSC frequency when the calibration is
disabled.
Modified:
stable/11/sys/x86/x86/tsc.c
Directory Properties:
stable/11/ (props changed)
Modified: stable/11/sys/x86/x86/tsc.c
==============================================================================
--- stable/11/sys/x86/x86/tsc.c Wed May 2 07:40:04 2018 (r333160)
+++ stable/11/sys/x86/x86/tsc.c Wed May 2 07:42:47 2018 (r333161)
@@ -128,6 +128,26 @@ tsc_freq_vmware(void)
tsc_is_invariant = 1;
}
+/*
+ * Calculate TSC frequency using information from the CPUID leaf 0x15
+ * 'Time Stamp Counter and Nominal Core Crystal Clock'. It should be
+ * an improvement over the parsing of the CPU model name in
+ * tsc_freq_intel(), when available.
+ */
+static bool
+tsc_freq_cpuid(void)
+{
+ u_int regs[4];
+
+ if (cpu_high < 0x15)
+ return (false);
+ do_cpuid(0x15, regs);
+ if (regs[0] == 0 || regs[1] == 0 || regs[2] == 0)
+ return (false);
+ tsc_freq = (uint64_t)regs[2] * regs[1] / regs[0];
+ return (true);
+}
+
static void
tsc_freq_intel(void)
{
@@ -252,17 +272,18 @@ probe_tsc_freq(void)
}
if (tsc_skip_calibration) {
- if (cpu_vendor_id == CPU_VENDOR_INTEL)
+ if (tsc_freq_cpuid())
+ ;
+ else if (cpu_vendor_id == CPU_VENDOR_INTEL)
tsc_freq_intel();
- return;
+ } else {
+ if (bootverbose)
+ printf("Calibrating TSC clock ... ");
+ tsc1 = rdtsc();
+ DELAY(1000000);
+ tsc2 = rdtsc();
+ tsc_freq = tsc2 - tsc1;
}
-
- if (bootverbose)
- printf("Calibrating TSC clock ... ");
- tsc1 = rdtsc();
- DELAY(1000000);
- tsc2 = rdtsc();
- tsc_freq = tsc2 - tsc1;
if (bootverbose)
printf("TSC clock: %ju Hz\n", (intmax_t)tsc_freq);
}
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