Recent x86 CPUs come with a constant time stamp counter. If this is

the case we verify if the CPU supports a specific version of the
architectural performance monitoring feature and read out the current
frequency from the fixed-function performance counter of the unhalted
core.

My initial motivation to implement this was the Soekris net6501-70
which comes with an Intel Atom E6xx 1.60GHz CPU.  It has a constant
time stamp counter plus speed step support and boots on the lowest
frequency of 600MHz.  This caused hw.cpuspeed and hw.setperf to
reflect the wrong values.

The diff is a cooperation work with jsg@.  The fixed-function
performance counter read code comes from a former diff of him.

OK jsg@

2 files changed, 44 insertions, 2 deletions

diff --git a/sys/arch/amd64/include/cpu.h b/sys/arch/amd64/include/cpu.h
index 9ce437af9de..60a095eed9e 100644
--- a/sys/arch/amd64/include/cpu.h
+++ b/sys/arch/amd64/include/cpu.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: cpu.h,v 1.74 2012/10/09 04:40:36 jsg Exp $	*/
+/*	$OpenBSD: cpu.h,v 1.75 2012/11/10 09:45:05 mglocker Exp $	*/
 /*	$NetBSD: cpu.h,v 1.1 2003/04/26 18:39:39 fvdl Exp $	*/
 
 /*-
@@ -138,6 +138,8 @@ struct cpu_info {
 #define CPUF_IDENTIFY	0x0010		/* CPU may now identify */
 #define CPUF_IDENTIFIED	0x0020		/* CPU has been identified */
 
+#define CPUF_CONST_TSC	0x0040		/* CPU has constant TSC */
+
 #define CPUF_PRESENT	0x1000		/* CPU is present */
 #define CPUF_RUNNING	0x2000		/* CPU is running */
 #define CPUF_PAUSE	0x4000		/* CPU is paused in DDB */
@@ -258,6 +260,10 @@ extern int biosextmem;
 extern int cpu;
 extern int cpu_feature;
 extern int cpu_ecxfeature;
+extern int cpu_perf_eax;
+extern int cpu_perf_ebx;
+extern int cpu_perf_edx;
+extern int cpu_apmi_edx;
 extern int ecpu_ecxfeature;
 extern int cpu_id;
 extern char cpu_vendor[];
diff --git a/sys/arch/amd64/include/specialreg.h b/sys/arch/amd64/include/specialreg.h
index 142fbbcbd57..f094f14c7ff 100644
--- a/sys/arch/amd64/include/specialreg.h
+++ b/sys/arch/amd64/include/specialreg.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: specialreg.h,v 1.23 2012/10/09 09:16:09 jsg Exp $	*/
+/*	$OpenBSD: specialreg.h,v 1.24 2012/11/10 09:45:05 mglocker Exp $	*/
 /*	$NetBSD: specialreg.h,v 1.1 2003/04/26 18:39:48 fvdl Exp $	*/
 /*	$NetBSD: x86/specialreg.h,v 1.2 2003/04/25 21:54:30 fvdl Exp $	*/
 
@@ -177,6 +177,27 @@
 #define	SEFF0EBX_ADX		0x00080000 /* ADCX/ADOX instructions */
 #define	SEFF0EBX_SMAP		0x00100000 /* Supervisor mode access prevent */
 
+ /*
+  * "Architectural Performance Monitoring" bits (CPUID function 0x0a):
+  * EAX bits, EBX bits, EDX bits.
+  */
+
+#define CPUIDEAX_VERID			0x000000ff /* Version ID */
+#define CPUIDEAX_NUM_GC(cpuid)		(((cpuid) >>  8) & 0x000000ff)
+#define CPUIDEAX_BIT_GC(cpuid)		(((cpuid) >> 16) & 0x000000ff)
+#define CPUIDEAX_LEN_EBX(cpuid)		(((cpuid) >> 24) & 0x000000ff)
+
+#define CPUIDEBX_EVT_CORE		(1 << 0) /* Core cycle */
+#define CPUIDEBX_EVT_INST		(1 << 1) /* Instruction retired */
+#define CPUIDEBX_EVT_REFR		(1 << 2) /* Reference cycles */
+#define CPUIDEBX_EVT_CACHE_REF		(1 << 3) /* Last-level cache ref. */
+#define CPUIDEBX_EVT_CACHE_MIS		(1 << 4) /* Last-level cache miss. */
+#define CPUIDEBX_EVT_BRANCH_INST	(1 << 5) /* Branch instruction ret. */
+#define CPUIDEBX_EVT_BRANCH_MISP	(1 << 6) /* Branch mispredict ret. */
+
+#define CPUIDEDX_NUM_FC(cpuid)		(((cpuid) >> 0) & 0x0000001f)
+#define CPUIDEDX_BIT_FC(cpuid)		(((cpuid) >> 5) & 0x000000ff)
+
 /*
  * CPUID "extended features" bits (CPUID function 0x80000001):
  * EDX bits, then ECX bits
@@ -214,6 +235,13 @@
 #define	CPUIDECX_TBM		0x00200000 /* Trailing bit manipulation instruction */
 #define	CPUIDECX_TOPEXT		0x00400000 /* Topology extensions support */
 
+/*
+ * "Advanced Power Management Information" bits (CPUID function 0x80000007):
+ * EDX bits.
+ */
+
+#define CPUIDEDX_ITSC		(1 << 8)	/* Invariant TSC */
+
 #define	CPUID2FAMILY(cpuid)	(((cpuid) >> 8) & 15)
 #define	CPUID2MODEL(cpuid)	(((cpuid) >> 4) & 15)
 #define	CPUID2STEPPING(cpuid)	((cpuid) & 15)
@@ -310,6 +338,14 @@
 #define	MSR_MTRRfix4K_F8000	0x26f
 #define MSR_CR_PAT		0x277
 #define MSR_MTRRdefType		0x2ff
+#define MSR_PERF_FIXED_CTR1	0x30a	/* CPU_CLK_Unhalted.Core */
+#define MSR_PERF_FIXED_CTR2	0x30b	/* CPU_CLK.Unhalted.Ref */
+#define MSR_PERF_FIXED_CTR_CTRL	0x38d
+#define MSR_PERF_FIXED_CTR1_EN	(1 << 4)
+#define MSR_PERF_FIXED_CTR2_EN	(1 << 8)
+#define MSR_PERF_GLOBAL_CTRL	0x38f
+#define MSR_PERF_GLOBAL_CTR1_EN	(1ULL << 33)
+#define MSR_PERF_GLOBAL_CTR2_EN	(1ULL << 34)
 #define MSR_MC0_CTL		0x400
 #define MSR_MC0_STATUS		0x401
 #define MSR_MC0_ADDR		0x402