[CPUFREQ] speedstep-centrino and acpi-cpufreq: P4 TSC rate is constant

From: "Pallipadi, Venkatesh" <venkatesh.pallipadi@intel.com>

In P4, CPU tsc rate won't change with CPU frequency change while using Enhanced
Speedstep Technology. Tested with both speedstep-centrino and acpi-cpufreq on
both i386 and x86-64.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Dominik Brodowski <linux@brodo.de>
Signed-off-by: Dave Jones <davej@redhat.com>

3 files changed, 40 insertions, 0 deletions

diff --git a/arch/i386/kernel/cpu/cpufreq/acpi-cpufreq.c b/arch/i386/kernel/cpu/cpufreq/acpi-cpufreq.c
index 79607ef603798b..963e17aa205d60 100644
--- a/arch/i386/kernel/cpu/cpufreq/acpi-cpufreq.c
+++ b/arch/i386/kernel/cpu/cpufreq/acpi-cpufreq.c
@@ -38,6 +38,8 @@
 #include <linux/acpi.h>
 #include <acpi/processor.h>
 
+#include "speedstep-est-common.h"
+
 #define dprintk(msg...) cpufreq_debug_printk(CPUFREQ_DEBUG_DRIVER, "acpi-cpufreq", msg)
 
 MODULE_AUTHOR("Paul Diefenbaugh, Dominik Brodowski");
@@ -53,6 +55,7 @@ struct cpufreq_acpi_io {
 
 static struct cpufreq_acpi_io	*acpi_io_data[NR_CPUS];
 
+static struct cpufreq_driver acpi_cpufreq_driver;
 
 static int
 acpi_processor_write_port(
@@ -374,6 +377,10 @@ acpi_cpufreq_cpu_init (
 	if (result)
 		goto err_free;
 
+	if (is_const_loops_cpu(cpu)) {
+		acpi_cpufreq_driver.flags |= CPUFREQ_CONST_LOOPS;
+	}
+
 	/* capability check */
 	if (data->acpi_data.state_count <= 1) {
 		dprintk("No P-States\n");
diff --git a/arch/i386/kernel/cpu/cpufreq/speedstep-centrino.c b/arch/i386/kernel/cpu/cpufreq/speedstep-centrino.c
index 2877bbe70441e9..2dfa9b16ddb7da 100644
--- a/arch/i386/kernel/cpu/cpufreq/speedstep-centrino.c
+++ b/arch/i386/kernel/cpu/cpufreq/speedstep-centrino.c
@@ -34,6 +34,8 @@
 #include <asm/processor.h>
 #include <asm/cpufeature.h>
 
+#include "speedstep-est-common.h"
+
 #define PFX		"speedstep-centrino: "
 #define MAINTAINER	"Jeremy Fitzhardinge <jeremy@goop.org>"
 
@@ -76,6 +78,8 @@ static int centrino_verify_cpu_id(const struct cpuinfo_x86 *c, const struct cpu_
 static struct cpu_model *centrino_model[NR_CPUS];
 static const struct cpu_id *centrino_cpu[NR_CPUS];
 
+static struct cpufreq_driver centrino_driver;
+
 #ifdef CONFIG_X86_SPEEDSTEP_CENTRINO_TABLE
 
 /* Computes the correct form for IA32_PERF_CTL MSR for a particular
@@ -508,6 +512,10 @@ static int centrino_cpu_init(struct cpufreq_policy *policy)
 	if (i != N_IDS)
 		centrino_cpu[policy->cpu] = &cpu_ids[i];
 
+	if (is_const_loops_cpu(policy->cpu)) {
+		centrino_driver.flags |= CPUFREQ_CONST_LOOPS;
+	}
+
 	if (centrino_cpu_init_acpi(policy)) {
 		if (policy->cpu != 0)
 			return -ENODEV;
diff --git a/arch/i386/kernel/cpu/cpufreq/speedstep-est-common.h b/arch/i386/kernel/cpu/cpufreq/speedstep-est-common.h
new file mode 100644
index 00000000000000..5ce995c9d866c1
--- /dev/null
+++ b/arch/i386/kernel/cpu/cpufreq/speedstep-est-common.h
@@ -0,0 +1,25 @@
+/*
+ * Routines common for drivers handling Enhanced Speedstep Technology
+ *  Copyright (C) 2004 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
+ *
+ *  Licensed under the terms of the GNU GPL License version 2 -- see
+ *  COPYING for details.
+ */
+
+static inline int is_const_loops_cpu(unsigned int cpu)
+{
+	struct cpuinfo_x86 	*c = cpu_data + cpu;
+
+	if (c->x86_vendor != X86_VENDOR_INTEL || !cpu_has(c, X86_FEATURE_EST))
+		return 0;
+
+	/*
+	 * on P-4s, the TSC runs with constant frequency independent of cpu freq
+	 * when we use EST
+	 */
+	if (c->x86 == 0xf)
+		return 1;
+
+	return 0;
+}
+