1 files changed, 715 insertions, 0 deletions

diff --git a/arch/i386/kernel/cpu/cpufreq/speedstep-centrino.c b/arch/i386/kernel/cpu/cpufreq/speedstep-centrino.c
new file mode 100644
index 000000000000..07d5612dc00f
--- /dev/null
+++ b/arch/i386/kernel/cpu/cpufreq/speedstep-centrino.c
@@ -0,0 +1,715 @@
+/*
+ * cpufreq driver for Enhanced SpeedStep, as found in Intel's Pentium
+ * M (part of the Centrino chipset).
+ *
+ * Despite the "SpeedStep" in the name, this is almost entirely unlike
+ * traditional SpeedStep.
+ *
+ * Modelled on speedstep.c
+ *
+ * Copyright (C) 2003 Jeremy Fitzhardinge <jeremy@goop.org>
+ *
+ * WARNING WARNING WARNING
+ *
+ * This driver manipulates the PERF_CTL MSR, which is only somewhat
+ * documented.  While it seems to work on my laptop, it has not been
+ * tested anywhere else, and it may not work for you, do strange
+ * things or simply crash.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/cpufreq.h>
+#include <linux/config.h>
+#include <linux/delay.h>
+#include <linux/compiler.h>
+
+#ifdef CONFIG_X86_SPEEDSTEP_CENTRINO_ACPI
+#include <linux/acpi.h>
+#include <acpi/processor.h>
+#endif
+
+#include <asm/msr.h>
+#include <asm/processor.h>
+#include <asm/cpufeature.h>
+
+#include "speedstep-est-common.h"
+
+#define PFX             "speedstep-centrino: "
+#define MAINTAINER      "Jeremy Fitzhardinge <jeremy@goop.org>"
+
+#define dprintk(msg...) cpufreq_debug_printk(CPUFREQ_DEBUG_DRIVER, "speedstep-centrino", msg)
+
+
+struct cpu_id
+{
+        __u8    x86;            /* CPU family */
+        __u8    x86_model;      /* model */
+        __u8    x86_mask;       /* stepping */
+};
+
+enum {
+        CPU_BANIAS,
+        CPU_DOTHAN_A1,
+        CPU_DOTHAN_A2,
+        CPU_DOTHAN_B0,
+};
+
+static const struct cpu_id cpu_ids[] = {
+        [CPU_BANIAS]    = { 6,  9, 5 },
+        [CPU_DOTHAN_A1] = { 6, 13, 1 },
+        [CPU_DOTHAN_A2] = { 6, 13, 2 },
+        [CPU_DOTHAN_B0] = { 6, 13, 6 },
+};
+#define N_IDS   (sizeof(cpu_ids)/sizeof(cpu_ids[0]))
+
+struct cpu_model
+{
+        const struct cpu_id *cpu_id;
+        const char      *model_name;
+        unsigned        max_freq; /* max clock in kHz */
+
+        struct cpufreq_frequency_table *op_points; /* clock/voltage pairs */
+};
+static int centrino_verify_cpu_id(const struct cpuinfo_x86 *c, const struct cpu_id *x);
+
+/* Operating points for current 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
+   frequency/voltage operating point; frequency in MHz, volts in mV.
+   This is stored as "index" in the structure. */
+#define OP(mhz, mv)                                                     \
+        {                                                               \
+                .frequency = (mhz) * 1000,                              \
+                .index = (((mhz)/100) << 8) | ((mv - 700) / 16)         \
+        }
+
+/*
+ * These voltage tables were derived from the Intel Pentium M
+ * datasheet, document 25261202.pdf, Table 5.  I have verified they
+ * are consistent with my IBM ThinkPad X31, which has a 1.3GHz Pentium
+ * M.
+ */
+
+/* Ultra Low Voltage Intel Pentium M processor 900MHz (Banias) */
+static struct cpufreq_frequency_table banias_900[] =
+{
+        OP(600,  844),
+        OP(800,  988),
+        OP(900, 1004),
+        { .frequency = CPUFREQ_TABLE_END }
+};
+
+/* Ultra Low Voltage Intel Pentium M processor 1000MHz (Banias) */
+static struct cpufreq_frequency_table banias_1000[] =
+{
+        OP(600,   844),
+        OP(800,   972),
+        OP(900,   988),
+        OP(1000, 1004),
+        { .frequency = CPUFREQ_TABLE_END }
+};
+
+/* Low Voltage Intel Pentium M processor 1.10GHz (Banias) */
+static struct cpufreq_frequency_table banias_1100[] =
+{
+        OP( 600,  956),
+        OP( 800, 1020),
+        OP( 900, 1100),
+        OP(1000, 1164),
+        OP(1100, 1180),
+        { .frequency = CPUFREQ_TABLE_END }
+};
+
+
+/* Low Voltage Intel Pentium M processor 1.20GHz (Banias) */
+static struct cpufreq_frequency_table banias_1200[] =
+{
+        OP( 600,  956),
+        OP( 800, 1004),
+        OP( 900, 1020),
+        OP(1000, 1100),
+        OP(1100, 1164),
+        OP(1200, 1180),
+        { .frequency = CPUFREQ_TABLE_END }
+};
+
+/* Intel Pentium M processor 1.30GHz (Banias) */
+static struct cpufreq_frequency_table banias_1300[] =
+{
+        OP( 600,  956),
+        OP( 800, 1260),
+        OP(1000, 1292),
+        OP(1200, 1356),
+        OP(1300, 1388),
+        { .frequency = CPUFREQ_TABLE_END }
+};
+
+/* Intel Pentium M processor 1.40GHz (Banias) */
+static struct cpufreq_frequency_table banias_1400[] =
+{
+        OP( 600,  956),
+        OP( 800, 1180),
+        OP(1000, 1308),
+        OP(1200, 1436),
+        OP(1400, 1484),
+        { .frequency = CPUFREQ_TABLE_END }
+};
+
+/* Intel Pentium M processor 1.50GHz (Banias) */
+static struct cpufreq_frequency_table banias_1500[] =
+{
+        OP( 600,  956),
+        OP( 800, 1116),
+        OP(1000, 1228),
+        OP(1200, 1356),
+        OP(1400, 1452),
+        OP(1500, 1484),
+        { .frequency = CPUFREQ_TABLE_END }
+};
+
+/* Intel Pentium M processor 1.60GHz (Banias) */
+static struct cpufreq_frequency_table banias_1600[] =
+{
+        OP( 600,  956),
+        OP( 800, 1036),
+        OP(1000, 1164),
+        OP(1200, 1276),
+        OP(1400, 1420),
+        OP(1600, 1484),
+        { .frequency = CPUFREQ_TABLE_END }
+};
+
+/* Intel Pentium M processor 1.70GHz (Banias) */
+static struct cpufreq_frequency_table banias_1700[] =
+{
+        OP( 600,  956),
+        OP( 800, 1004),
+        OP(1000, 1116),
+        OP(1200, 1228),
+        OP(1400, 1308),
+        OP(1700, 1484),
+        { .frequency = CPUFREQ_TABLE_END }
+};
+#undef OP
+
+#define _BANIAS(cpuid, max, name)       \
+{       .cpu_id         = cpuid,        \
+        .model_name     = "Intel(R) Pentium(R) M processor " name "MHz", \
+        .max_freq       = (max)*1000,   \
+        .op_points      = banias_##max, \
+}
+#define BANIAS(max)     _BANIAS(&cpu_ids[CPU_BANIAS], max, #max)
+
+/* CPU models, their operating frequency range, and freq/voltage
+   operating points */
+static struct cpu_model models[] =
+{
+        _BANIAS(&cpu_ids[CPU_BANIAS], 900, " 900"),
+        BANIAS(1000),
+        BANIAS(1100),
+        BANIAS(1200),
+        BANIAS(1300),
+        BANIAS(1400),
+        BANIAS(1500),
+        BANIAS(1600),
+        BANIAS(1700),
+
+        /* NULL model_name is a wildcard */
+        { &cpu_ids[CPU_DOTHAN_A1], NULL, 0, NULL },
+        { &cpu_ids[CPU_DOTHAN_A2], NULL, 0, NULL },
+        { &cpu_ids[CPU_DOTHAN_B0], NULL, 0, NULL },
+
+        { NULL, }
+};
+#undef _BANIAS
+#undef BANIAS
+
+static int centrino_cpu_init_table(struct cpufreq_policy *policy)
+{
+        struct cpuinfo_x86 *cpu = &cpu_data[policy->cpu];
+        struct cpu_model *model;
+
+        for(model = models; model->cpu_id != NULL; model++)
+                if (centrino_verify_cpu_id(cpu, model->cpu_id) &&
+                    (model->model_name == NULL ||
+                     strcmp(cpu->x86_model_id, model->model_name) == 0))
+                        break;
+
+        if (model->cpu_id == NULL) {
+                /* No match at all */
+                dprintk(KERN_INFO PFX "no support for CPU model \"%s\": "
+                       "send /proc/cpuinfo to " MAINTAINER "\n",
+                       cpu->x86_model_id);
+                return -ENOENT;
+        }
+
+        if (model->op_points == NULL) {
+                /* Matched a non-match */
+                dprintk(KERN_INFO PFX "no table support for CPU model \"%s\": \n",
+                       cpu->x86_model_id);
+#ifndef CONFIG_X86_SPEEDSTEP_CENTRINO_ACPI
+                dprintk(KERN_INFO PFX "try compiling with CONFIG_X86_SPEEDSTEP_CENTRINO_ACPI enabled\n");
+#endif
+                return -ENOENT;
+        }
+
+        centrino_model[policy->cpu] = model;
+
+        dprintk("found \"%s\": max frequency: %dkHz\n",
+               model->model_name, model->max_freq);
+
+        return 0;
+}
+
+#else
+static inline int centrino_cpu_init_table(struct cpufreq_policy *policy) { return -ENODEV; }
+#endif /* CONFIG_X86_SPEEDSTEP_CENTRINO_TABLE */
+
+static int centrino_verify_cpu_id(const struct cpuinfo_x86 *c, const struct cpu_id *x)
+{
+        if ((c->x86 == x->x86) &&
+            (c->x86_model == x->x86_model) &&
+            (c->x86_mask == x->x86_mask))
+                return 1;
+        return 0;
+}
+
+/* To be called only after centrino_model is initialized */
+static unsigned extract_clock(unsigned msr, unsigned int cpu, int failsafe)
+{
+        int i;
+
+        /*
+         * Extract clock in kHz from PERF_CTL value
+         * for centrino, as some DSDTs are buggy.
+         * Ideally, this can be done using the acpi_data structure.
+         */
+        if ((centrino_cpu[cpu] == &cpu_ids[CPU_BANIAS]) ||
+            (centrino_cpu[cpu] == &cpu_ids[CPU_DOTHAN_A1]) ||
+            (centrino_cpu[cpu] == &cpu_ids[CPU_DOTHAN_B0])) {
+                msr = (msr >> 8) & 0xff;
+                return msr * 100000;
+        }
+
+        if ((!centrino_model[cpu]) || (!centrino_model[cpu]->op_points))
+                return 0;
+
+        msr &= 0xffff;
+        for (i=0;centrino_model[cpu]->op_points[i].frequency != CPUFREQ_TABLE_END; i++) {
+                if (msr == centrino_model[cpu]->op_points[i].index)
+                        return centrino_model[cpu]->op_points[i].frequency;
+        }
+        if (failsafe)
+                return centrino_model[cpu]->op_points[i-1].frequency;
+        else
+                return 0;
+}
+
+/* Return the current CPU frequency in kHz */
+static unsigned int get_cur_freq(unsigned int cpu)
+{
+        unsigned l, h;
+        unsigned clock_freq;
+        cpumask_t saved_mask;
+
+        saved_mask = current->cpus_allowed;
+        set_cpus_allowed(current, cpumask_of_cpu(cpu));
+        if (smp_processor_id() != cpu)
+                return 0;
+
+        rdmsr(MSR_IA32_PERF_STATUS, l, h);
+        clock_freq = extract_clock(l, cpu, 0);
+
+        if (unlikely(clock_freq == 0)) {
+                /*
+                 * On some CPUs, we can see transient MSR values (which are
+                 * not present in _PSS), while CPU is doing some automatic
+                 * P-state transition (like TM2). Get the last freq set 
+                 * in PERF_CTL.
+                 */
+                rdmsr(MSR_IA32_PERF_CTL, l, h);
+                clock_freq = extract_clock(l, cpu, 1);
+        }
+
+        set_cpus_allowed(current, saved_mask);
+        return clock_freq;
+}
+
+
+#ifdef CONFIG_X86_SPEEDSTEP_CENTRINO_ACPI
+
+static struct acpi_processor_performance p;
+
+/*
+ * centrino_cpu_init_acpi - register with ACPI P-States library
+ *
+ * Register with the ACPI P-States library (part of drivers/acpi/processor.c)
+ * in order to determine correct frequency and voltage pairings by reading
+ * the _PSS of the ACPI DSDT or SSDT tables.
+ */
+static int centrino_cpu_init_acpi(struct cpufreq_policy *policy)
+{
+        union acpi_object               arg0 = {ACPI_TYPE_BUFFER};
+        u32                             arg0_buf[3];
+        struct acpi_object_list         arg_list = {1, &arg0};
+        unsigned long                   cur_freq;
+        int                             result = 0, i;
+        unsigned int                    cpu = policy->cpu;
+
+        /* _PDC settings */
+        arg0.buffer.length = 12;
+        arg0.buffer.pointer = (u8 *) arg0_buf;
+        arg0_buf[0] = ACPI_PDC_REVISION_ID;
+        arg0_buf[1] = 1;
+        arg0_buf[2] = ACPI_PDC_EST_CAPABILITY_SMP | ACPI_PDC_EST_CAPABILITY_MSR;
+
+        p.pdc = &arg_list;
+
+        /* register with ACPI core */
+        if (acpi_processor_register_performance(&p, cpu)) {
+                dprintk(KERN_INFO PFX "obtaining ACPI data failed\n");
+                return -EIO;
+        }
+
+        /* verify the acpi_data */
+        if (p.state_count <= 1) {
+                dprintk("No P-States\n");
+                result = -ENODEV;
+                goto err_unreg;
+        }
+
+        if ((p.control_register.space_id != ACPI_ADR_SPACE_FIXED_HARDWARE) ||
+            (p.status_register.space_id != ACPI_ADR_SPACE_FIXED_HARDWARE)) {
+                dprintk("Invalid control/status registers (%x - %x)\n",
+                        p.control_register.space_id, p.status_register.space_id);
+                result = -EIO;
+                goto err_unreg;
+        }
+
+        for (i=0; i<p.state_count; i++) {
+                if (p.states[i].control != p.states[i].status) {
+                        dprintk("Different control (%x) and status values (%x)\n",
+                                p.states[i].control, p.states[i].status);
+                        result = -EINVAL;
+                        goto err_unreg;
+                }
+
+                if (!p.states[i].core_frequency) {
+                        dprintk("Zero core frequency for state %u\n", i);
+                        result = -EINVAL;
+                        goto err_unreg;
+                }
+
+                if (p.states[i].core_frequency > p.states[0].core_frequency) {
+                        dprintk("P%u has larger frequency (%u) than P0 (%u), skipping\n", i,
+                                p.states[i].core_frequency, p.states[0].core_frequency);
+                        p.states[i].core_frequency = 0;
+                        continue;
+                }
+        }
+
+        centrino_model[cpu] = kmalloc(sizeof(struct cpu_model), GFP_KERNEL);
+        if (!centrino_model[cpu]) {
+                result = -ENOMEM;
+                goto err_unreg;
+        }
+        memset(centrino_model[cpu], 0, sizeof(struct cpu_model));
+
+        centrino_model[cpu]->model_name=NULL;
+        centrino_model[cpu]->max_freq = p.states[0].core_frequency * 1000;
+        centrino_model[cpu]->op_points =  kmalloc(sizeof(struct cpufreq_frequency_table) *
+                                             (p.state_count + 1), GFP_KERNEL);
+        if (!centrino_model[cpu]->op_points) {
+                result = -ENOMEM;
+                goto err_kfree;
+        }
+
+        for (i=0; i<p.state_count; i++) {
+                centrino_model[cpu]->op_points[i].index = p.states[i].control;
+                centrino_model[cpu]->op_points[i].frequency = p.states[i].core_frequency * 1000;
+                dprintk("adding state %i with frequency %u and control value %04x\n", 
+                        i, centrino_model[cpu]->op_points[i].frequency, centrino_model[cpu]->op_points[i].index);
+        }
+        centrino_model[cpu]->op_points[p.state_count].frequency = CPUFREQ_TABLE_END;
+
+        cur_freq = get_cur_freq(cpu);
+
+        for (i=0; i<p.state_count; i++) {
+                if (!p.states[i].core_frequency) {
+                        dprintk("skipping state %u\n", i);
+                        centrino_model[cpu]->op_points[i].frequency = CPUFREQ_ENTRY_INVALID;
+                        continue;
+                }
+                
+                if (extract_clock(centrino_model[cpu]->op_points[i].index, cpu, 0) !=
+                    (centrino_model[cpu]->op_points[i].frequency)) {
+                        dprintk("Invalid encoded frequency (%u vs. %u)\n",
+                                extract_clock(centrino_model[cpu]->op_points[i].index, cpu, 0),
+                                centrino_model[cpu]->op_points[i].frequency);
+                        result = -EINVAL;
+                        goto err_kfree_all;
+                }
+
+                if (cur_freq == centrino_model[cpu]->op_points[i].frequency)
+                        p.state = i;
+        }
+
+        /* notify BIOS that we exist */
+        acpi_processor_notify_smm(THIS_MODULE);
+
+        return 0;
+
+ err_kfree_all:
+        kfree(centrino_model[cpu]->op_points);
+ err_kfree:
+        kfree(centrino_model[cpu]);
+ err_unreg:
+        acpi_processor_unregister_performance(&p, cpu);
+        dprintk(KERN_INFO PFX "invalid ACPI data\n");
+        return (result);
+}
+#else
+static inline int centrino_cpu_init_acpi(struct cpufreq_policy *policy) { return -ENODEV; }
+#endif
+
+static int centrino_cpu_init(struct cpufreq_policy *policy)
+{
+        struct cpuinfo_x86 *cpu = &cpu_data[policy->cpu];
+        unsigned freq;
+        unsigned l, h;
+        int ret;
+        int i;
+
+        /* Only Intel makes Enhanced Speedstep-capable CPUs */
+        if (cpu->x86_vendor != X86_VENDOR_INTEL || !cpu_has(cpu, X86_FEATURE_EST))
+                return -ENODEV;
+
+        for (i = 0; i < N_IDS; i++)
+                if (centrino_verify_cpu_id(cpu, &cpu_ids[i]))
+                        break;
+
+        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;
+
+                if (!centrino_cpu[policy->cpu]) {
+                        dprintk(KERN_INFO PFX "found unsupported CPU with "
+                        "Enhanced SpeedStep: send /proc/cpuinfo to "
+                        MAINTAINER "\n");
+                        return -ENODEV;
+                }
+
+                if (centrino_cpu_init_table(policy)) {
+                        return -ENODEV;
+                }
+        }
+
+        /* Check to see if Enhanced SpeedStep is enabled, and try to
+           enable it if not. */
+        rdmsr(MSR_IA32_MISC_ENABLE, l, h);
+
+        if (!(l & (1<<16))) {
+                l |= (1<<16);
+                dprintk("trying to enable Enhanced SpeedStep (%x)\n", l);
+                wrmsr(MSR_IA32_MISC_ENABLE, l, h);
+
+                /* check to see if it stuck */
+                rdmsr(MSR_IA32_MISC_ENABLE, l, h);
+                if (!(l & (1<<16))) {
+                        printk(KERN_INFO PFX "couldn't enable Enhanced SpeedStep\n");
+                        return -ENODEV;
+                }
+        }
+
+        freq = get_cur_freq(policy->cpu);
+
+        policy->governor = CPUFREQ_DEFAULT_GOVERNOR;
+        policy->cpuinfo.transition_latency = 10000; /* 10uS transition latency */
+        policy->cur = freq;
+
+        dprintk("centrino_cpu_init: cur=%dkHz\n", policy->cur);
+
+        ret = cpufreq_frequency_table_cpuinfo(policy, centrino_model[policy->cpu]->op_points);
+        if (ret)
+                return (ret);
+
+        cpufreq_frequency_table_get_attr(centrino_model[policy->cpu]->op_points, policy->cpu);
+
+        return 0;
+}
+
+static int centrino_cpu_exit(struct cpufreq_policy *policy)
+{
+        unsigned int cpu = policy->cpu;
+
+        if (!centrino_model[cpu])
+                return -ENODEV;
+
+        cpufreq_frequency_table_put_attr(cpu);
+
+#ifdef CONFIG_X86_SPEEDSTEP_CENTRINO_ACPI
+        if (!centrino_model[cpu]->model_name) {
+                dprintk("unregistering and freeing ACPI data\n");
+                acpi_processor_unregister_performance(&p, cpu);
+                kfree(centrino_model[cpu]->op_points);
+                kfree(centrino_model[cpu]);
+        }
+#endif
+
+        centrino_model[cpu] = NULL;
+
+        return 0;
+}
+
+/**
+ * centrino_verify - verifies a new CPUFreq policy
+ * @policy: new policy
+ *
+ * Limit must be within this model's frequency range at least one
+ * border included.
+ */
+static int centrino_verify (struct cpufreq_policy *policy)
+{
+        return cpufreq_frequency_table_verify(policy, centrino_model[policy->cpu]->op_points);
+}
+
+/**
+ * centrino_setpolicy - set a new CPUFreq policy
+ * @policy: new policy
+ * @target_freq: the target frequency
+ * @relation: how that frequency relates to achieved frequency (CPUFREQ_RELATION_L or CPUFREQ_RELATION_H)
+ *
+ * Sets a new CPUFreq policy.
+ */
+static int centrino_target (struct cpufreq_policy *policy,
+                            unsigned int target_freq,
+                            unsigned int relation)
+{
+        unsigned int    newstate = 0;
+        unsigned int    msr, oldmsr, h, cpu = policy->cpu;
+        struct cpufreq_freqs    freqs;
+        cpumask_t               saved_mask;
+        int                     retval;
+
+        if (centrino_model[cpu] == NULL)
+                return -ENODEV;
+
+        /*
+         * Support for SMP systems.
+         * Make sure we are running on the CPU that wants to change frequency
+         */
+        saved_mask = current->cpus_allowed;
+        set_cpus_allowed(current, policy->cpus);
+        if (!cpu_isset(smp_processor_id(), policy->cpus)) {
+                dprintk("couldn't limit to CPUs in this domain\n");
+                return(-EAGAIN);
+        }
+
+        if (cpufreq_frequency_table_target(policy, centrino_model[cpu]->op_points, target_freq,
+                                           relation, &newstate)) {
+                retval = -EINVAL;
+                goto migrate_end;
+        }
+
+        msr = centrino_model[cpu]->op_points[newstate].index;
+        rdmsr(MSR_IA32_PERF_CTL, oldmsr, h);
+
+        if (msr == (oldmsr & 0xffff)) {
+                retval = 0;
+                dprintk("no change needed - msr was and needs to be %x\n", oldmsr);
+                goto migrate_end;
+        }
+
+        freqs.cpu = cpu;
+        freqs.old = extract_clock(oldmsr, cpu, 0);
+        freqs.new = extract_clock(msr, cpu, 0);
+
+        dprintk("target=%dkHz old=%d new=%d msr=%04x\n",
+                target_freq, freqs.old, freqs.new, msr);
+
+        cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
+
+        /* all but 16 LSB are "reserved", so treat them with
+           care */
+        oldmsr &= ~0xffff;
+        msr &= 0xffff;
+        oldmsr |= msr;
+
+        wrmsr(MSR_IA32_PERF_CTL, oldmsr, h);
+
+        cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
+
+        retval = 0;
+migrate_end:
+        set_cpus_allowed(current, saved_mask);
+        return (retval);
+}
+
+static struct freq_attr* centrino_attr[] = {
+        &cpufreq_freq_attr_scaling_available_freqs,
+        NULL,
+};
+
+static struct cpufreq_driver centrino_driver = {
+        .name           = "centrino", /* should be speedstep-centrino,
+                                         but there's a 16 char limit */
+        .init           = centrino_cpu_init,
+        .exit           = centrino_cpu_exit,
+        .verify         = centrino_verify,
+        .target         = centrino_target,
+        .get            = get_cur_freq,
+        .attr           = centrino_attr,
+        .owner          = THIS_MODULE,
+};
+
+
+/**
+ * centrino_init - initializes the Enhanced SpeedStep CPUFreq driver
+ *
+ * Initializes the Enhanced SpeedStep support. Returns -ENODEV on
+ * unsupported devices, -ENOENT if there's no voltage table for this
+ * particular CPU model, -EINVAL on problems during initiatization,
+ * and zero on success.
+ *
+ * This is quite picky.  Not only does the CPU have to advertise the
+ * "est" flag in the cpuid capability flags, we look for a specific
+ * CPU model and stepping, and we need to have the exact model name in
+ * our voltage tables.  That is, be paranoid about not releasing
+ * someone's valuable magic smoke.
+ */
+static int __init centrino_init(void)
+{
+        struct cpuinfo_x86 *cpu = cpu_data;
+
+        if (!cpu_has(cpu, X86_FEATURE_EST))
+                return -ENODEV;
+
+        return cpufreq_register_driver(&centrino_driver);
+}
+
+static void __exit centrino_exit(void)
+{
+        cpufreq_unregister_driver(&centrino_driver);
+}
+
+MODULE_AUTHOR ("Jeremy Fitzhardinge <jeremy@goop.org>");
+MODULE_DESCRIPTION ("Enhanced SpeedStep driver for Intel Pentium M processors.");
+MODULE_LICENSE ("GPL");
+
+late_initcall(centrino_init);
+module_exit(centrino_exit);