From: Damjan Marion <damarion@cisco.com>
Date: Wed, 18 Dec 2019 17:45:19 +0000 (+0100)
Subject: vppinfra: use CPUID provided base frequency if available
X-Git-Tag: v20.09-rc0~708
X-Git-Url: https://gerrit.fd.io/r/gitweb?p=vpp.git;a=commitdiff_plain;h=12e3e312b1c9ea83342a504786e0eb36ede2d9d5

vppinfra: use CPUID provided base frequency if available

Type: fix

Change-Id: Ifb007207be97119e07c3a0eba4714eb519de043c
Signed-off-by: Damjan Marion <damarion@cisco.com>
---

diff --git a/src/vppinfra/time.c b/src/vppinfra/time.c
index bfc48ce0671..35852a61cdf 100644
--- a/src/vppinfra/time.c
+++ b/src/vppinfra/time.c
@@ -153,6 +153,38 @@ os_cpu_clock_frequency (void)
 #endif
   f64 cpu_freq;
 
+#ifdef __x86_64__
+  u32 __clib_unused eax = 0, ebx = 0, ecx = 0, edx = 0;
+  clib_get_cpuid (0x00, &eax, &ebx, &ecx, &edx);
+  if (eax >= 0x15)
+    {
+      u32 max_leaf = eax;
+      /*
+         CPUID Leaf 0x15 - Time Stamp Counter and Nominal Core Crystal Clock Info
+         eax - denominator of the TSC/”core crystal clock” ratio
+         ebx - numerator of the TSC/”core crystal clock” ratio
+         ecx - nominal frequency of the core crystal clock in Hz
+         edx - reseved
+       */
+
+      clib_get_cpuid (0x15, &eax, &ebx, &ecx, &edx);
+      if (ebx && ecx)
+	return ecx * ebx / eax;
+
+      if (max_leaf >= 0x16)
+	{
+	  /*
+	     CPUID Leaf 0x16 - Processor Frequency Information Leaf
+	     eax - Bits 15 - 00: Processor Base Frequency (in MHz).
+	   */
+
+	  clib_get_cpuid (0x16, &eax, &ebx, &ecx, &edx);
+	  if (eax)
+	    return 1e6 * (eax & 0xffff);
+	}
+    }
+#endif
+
   if (clib_cpu_supports_invariant_tsc ())
     return estimate_clock_frequency (1e-3);