// SPDX-License-Identifier: GPL-2.0-only
/*
 * coretemp.c - Linux kernel module for hardware monitoring
 *
 * Copyright (C) 2007 Rudolf Marek <r.marek@assembler.cz>
 *
 * Inspired from many hwmon drivers
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/jiffies.h>
#include <linux/hwmon.h>
#include <linux/sysfs.h>
#include <linux/hwmon-sysfs.h>
#include <linux/err.h>
#include <linux/mutex.h>
#include <linux/list.h>
#include <linux/platform_device.h>
#include <linux/cpu.h>
#include <linux/smp.h>
#include <linux/moduleparam.h>
#include <linux/pci.h>
#include <asm/msr.h>
#include <asm/processor.h>
#include <asm/cpu_device_id.h>

#define DRVNAME "coretemp"

/*
 * force_tjmax only matters when TjMax can't be read from the CPU itself.
 * When set, it replaces the driver's suboptimal heuristic.
 */
static int force_tjmax;
module_param_named(tjmax, force_tjmax, int, 0444);
MODULE_PARM_DESC(tjmax, "TjMax value in degrees Celsius");

#define PKG_SYSFS_ATTR_NO       1       /* Sysfs attribute for package temp */
#define BASE_SYSFS_ATTR_NO      2       /* Sysfs Base attr no for coretemp */
#define NUM_REAL_CORES          128     /* Number of Real cores per cpu */
#define CORETEMP_NAME_LENGTH    19      /* String Length of attrs */
#define MAX_CORE_ATTRS          4       /* Maximum no of basic attrs */
#define TOTAL_ATTRS             (MAX_CORE_ATTRS + 1)
#define MAX_CORE_DATA           (NUM_REAL_CORES + BASE_SYSFS_ATTR_NO)

#define TO_CORE_ID(cpu)         (cpu_data(cpu).cpu_core_id)
#define TO_ATTR_NO(cpu)         (TO_CORE_ID(cpu) + BASE_SYSFS_ATTR_NO)

#ifdef CONFIG_SMP
#define for_each_sibling(i, cpu) \
        for_each_cpu(i, topology_sibling_cpumask(cpu))
#else
#define for_each_sibling(i, cpu)        for (i = 0; false; )
#endif

/*
 * Per-Core Temperature Data
 * @last_updated: The time when the current temperature value was updated
 *              earlier (in jiffies).
 * @cpu_core_id: The CPU Core from which temperature values should be read
 *              This value is passed as "id" field to rdmsr/wrmsr functions.
 * @status_reg: One of IA32_THERM_STATUS or IA32_PACKAGE_THERM_STATUS,
 *              from where the temperature values should be read.
 * @attr_size:  Total number of pre-core attrs displayed in the sysfs.
 * @is_pkg_data: If this is 1, the temp_data holds pkgtemp data.
 *              Otherwise, temp_data holds coretemp data.
 * @valid: If this is 1, the current temperature is valid.
 */
struct temp_data {
        int temp;
        int ttarget;
        int tjmax;
        unsigned long last_updated;
        unsigned int cpu;
        u32 cpu_core_id;
        u32 status_reg;
        int attr_size;
        bool is_pkg_data;
        bool valid;
        struct sensor_device_attribute sd_attrs[TOTAL_ATTRS];
        char attr_name[TOTAL_ATTRS][CORETEMP_NAME_LENGTH];
        struct attribute *attrs[TOTAL_ATTRS + 1];
        struct attribute_group attr_group;
        struct mutex update_lock;
};

/* Platform Data per Physical CPU */
struct platform_data {
        struct device           *hwmon_dev;
        u16                     pkg_id;
        struct cpumask          cpumask;
        struct temp_data        *core_data[MAX_CORE_DATA];
        struct device_attribute name_attr;
};

/* Keep track of how many zone pointers we allocated in init() */
static int max_zones __read_mostly;
/* Array of zone pointers. Serialized by cpu hotplug lock */
static struct platform_device **zone_devices;

static ssize_t show_label(struct device *dev,
                                struct device_attribute *devattr, char *buf)
{
        struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
        struct platform_data *pdata = dev_get_drvdata(dev);
        struct temp_data *tdata = pdata->core_data[attr->index];

        if (tdata->is_pkg_data)
                return sprintf(buf, "Package id %u\n", pdata->pkg_id);

        return sprintf(buf, "Core %u\n", tdata->cpu_core_id);
}

static ssize_t show_crit_alarm(struct device *dev,
                                struct device_attribute *devattr, char *buf)
{
        u32 eax, edx;
        struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
        struct platform_data *pdata = dev_get_drvdata(dev);
        struct temp_data *tdata = pdata->core_data[attr->index];

        mutex_lock(&tdata->update_lock);
        rdmsr_on_cpu(tdata->cpu, tdata->status_reg, &eax, &edx);
        mutex_unlock(&tdata->update_lock);

        return sprintf(buf, "%d\n", (eax >> 5) & 1);
}

static ssize_t show_tjmax(struct device *dev,
                        struct device_attribute *devattr, char *buf)
{
        struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
        struct platform_data *pdata = dev_get_drvdata(dev);

        return sprintf(buf, "%d\n", pdata->core_data[attr->index]->tjmax);
}

static ssize_t show_ttarget(struct device *dev,
                                struct device_attribute *devattr, char *buf)
{
        struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
        struct platform_data *pdata = dev_get_drvdata(dev);

        return sprintf(buf, "%d\n", pdata->core_data[attr->index]->ttarget);
}

static ssize_t show_temp(struct device *dev,
                        struct device_attribute *devattr, char *buf)
{
        u32 eax, edx;
        struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
        struct platform_data *pdata = dev_get_drvdata(dev);
        struct temp_data *tdata = pdata->core_data[attr->index];

        mutex_lock(&tdata->update_lock);

        /* Check whether the time interval has elapsed */
        if (!tdata->valid || time_after(jiffies, tdata->last_updated + HZ)) {
                rdmsr_on_cpu(tdata->cpu, tdata->status_reg, &eax, &edx);
                /*
                 * Ignore the valid bit. In all observed cases the register
                 * value is either low or zero if the valid bit is 0.
                 * Return it instead of reporting an error which doesn't
                 * really help at all.
                 */
                tdata->temp = tdata->tjmax - ((eax >> 16) & 0x7f) * 1000;
                tdata->valid = 1;
                tdata->last_updated = jiffies;
        }

        mutex_unlock(&tdata->update_lock);
        return sprintf(buf, "%d\n", tdata->temp);
}

struct tjmax_pci {
        unsigned int device;
        int tjmax;
};

static const struct tjmax_pci tjmax_pci_table[] = {
        { 0x0708, 110000 },     /* CE41x0 (Sodaville ) */
        { 0x0c72, 102000 },     /* Atom S1240 (Centerton) */
        { 0x0c73, 95000 },      /* Atom S1220 (Centerton) */
        { 0x0c75, 95000 },      /* Atom S1260 (Centerton) */
};

struct tjmax {
        char const *id;
        int tjmax;
};

static const struct tjmax tjmax_table[] = {
        { "CPU  230", 100000 },         /* Model 0x1c, stepping 2       */
        { "CPU  330", 125000 },         /* Model 0x1c, stepping 2       */
};

struct tjmax_model {
        u8 model;
        u8 mask;
        int tjmax;
};

#define ANY 0xff

static const struct tjmax_model tjmax_model_table[] = {
        { 0x1c, 10, 100000 },   /* D4xx, K4xx, N4xx, D5xx, K5xx, N5xx */
        { 0x1c, ANY, 90000 },   /* Z5xx, N2xx, possibly others
                                 * Note: Also matches 230 and 330,
                                 * which are covered by tjmax_table
                                 */
        { 0x26, ANY, 90000 },   /* Atom Tunnel Creek (Exx), Lincroft (Z6xx)
                                 * Note: TjMax for E6xxT is 110C, but CPU type
                                 * is undetectable by software
                                 */
        { 0x27, ANY, 90000 },   /* Atom Medfield (Z2460) */
        { 0x35, ANY, 90000 },   /* Atom Clover Trail/Cloverview (Z27x0) */
        { 0x36, ANY, 100000 },  /* Atom Cedar Trail/Cedarview (N2xxx, D2xxx)
                                 * Also matches S12x0 (stepping 9), covered by
                                 * PCI table
                                 */
};

static int adjust_tjmax(struct cpuinfo_x86 *c, u32 id, struct device *dev)
{
        /* The 100C is default for both mobile and non mobile CPUs */

        int tjmax = 100000;
        int tjmax_ee = 85000;
        int usemsr_ee = 1;
        int err;
        u32 eax, edx;
        int i;
        u16 devfn = PCI_DEVFN(0, 0);
        struct pci_dev *host_bridge = pci_get_domain_bus_and_slot(0, 0, devfn);

        /*
         * Explicit tjmax table entries override heuristics.
         * First try PCI host bridge IDs, followed by model ID strings
         * and model/stepping information.
         */
        if (host_bridge && host_bridge->vendor == PCI_VENDOR_ID_INTEL) {
                for (i = 0; i < ARRAY_SIZE(tjmax_pci_table); i++) {
                        if (host_bridge->device == tjmax_pci_table[i].device)
                                return tjmax_pci_table[i].tjmax;
                }
        }

        for (i = 0; i < ARRAY_SIZE(tjmax_table); i++) {
                if (strstr(c->x86_model_id, tjmax_table[i].id))
                        return tjmax_table[i].tjmax;
        }

        for (i = 0; i < ARRAY_SIZE(tjmax_model_table); i++) {
                const struct tjmax_model *tm = &tjmax_model_table[i];
                if (c->x86_model == tm->model &&
                    (tm->mask == ANY || c->x86_stepping == tm->mask))
                        return tm->tjmax;
        }

        /* Early chips have no MSR for TjMax */

        if (c->x86_model == 0xf && c->x86_stepping < 4)
                usemsr_ee = 0;

        if (c->x86_model > 0xe && usemsr_ee) {
                u8 platform_id;

                /*
                 * Now we can detect the mobile CPU using Intel provided table
                 * http://softwarecommunity.intel.com/Wiki/Mobility/720.htm
                 * For Core2 cores, check MSR 0x17, bit 28 1 = Mobile CPU
                 */
                err = rdmsr_safe_on_cpu(id, 0x17, &eax, &edx);
                if (err) {
                        dev_warn(dev,
                                 "Unable to access MSR 0x17, assuming desktop"
                                 " CPU\n");
                        usemsr_ee = 0;
                } else if (c->x86_model < 0x17 && !(eax & 0x10000000)) {
                        /*
                         * Trust bit 28 up to Penryn, I could not find any
                         * documentation on that; if you happen to know
                         * someone at Intel please ask
                         */
                        usemsr_ee = 0;
                } else {
                        /* Platform ID bits 52:50 (EDX starts at bit 32) */
                        platform_id = (edx >> 18) & 0x7;

                        /*
                         * Mobile Penryn CPU seems to be platform ID 7 or 5
                         * (guesswork)
                         */
                        if (c->x86_model == 0x17 &&
                            (platform_id == 5 || platform_id == 7)) {
                                /*
                                 * If MSR EE bit is set, set it to 90 degrees C,
                                 * otherwise 105 degrees C
                                 */
                                tjmax_ee = 90000;
                                tjmax = 105000;
                        }
                }
        }

        if (usemsr_ee) {
                err = rdmsr_safe_on_cpu(id, 0xee, &eax, &edx);
                if (err) {
                        dev_warn(dev,
                                 "Unable to access MSR 0xEE, for Tjmax, left"
                                 " at default\n");
                } else if (eax & 0x40000000) {
                        tjmax = tjmax_ee;
                }
        } else if (tjmax == 100000) {
                /*
                 * If we don't use msr EE it means we are desktop CPU
                 * (with exeception of Atom)
                 */
                dev_warn(dev, "Using relative temperature scale!\n");
        }

        return tjmax;
}

static bool cpu_has_tjmax(struct cpuinfo_x86 *c)
{
        u8 model = c->x86_model;

        return model > 0xe &&
               model != 0x1c &&
               model != 0x26 &&
               model != 0x27 &&
               model != 0x35 &&
               model != 0x36;
}

static int get_tjmax(struct cpuinfo_x86 *c, u32 id, struct device *dev)
{
        int err;
        u32 eax, edx;
        u32 val;

        /*
         * A new feature of current Intel(R) processors, the
         * IA32_TEMPERATURE_TARGET contains the TjMax value
         */
        err = rdmsr_safe_on_cpu(id, MSR_IA32_TEMPERATURE_TARGET, &eax, &edx);
        if (err) {
                if (cpu_has_tjmax(c))
                        dev_warn(dev, "Unable to read TjMax from CPU %u\n", id);
        } else {
                val = (eax >> 16) & 0xff;
                /*
                 * If the TjMax is not plausible, an assumption
                 * will be used
                 */
                if (val) {
                        dev_dbg(dev, "TjMax is %d degrees C\n", val);
                        return val * 1000;
                }
        }

        if (force_tjmax) {
                dev_notice(dev, "TjMax forced to %d degrees C by user\n",
                           force_tjmax);
                return force_tjmax * 1000;
        }

        /*
         * An assumption is made for early CPUs and unreadable MSR.
         * NOTE: the calculated value may not be correct.
         */
        return adjust_tjmax(c, id, dev);
}

static int create_core_attrs(struct temp_data *tdata, struct device *dev,
                             int attr_no)
{
        int i;
        static ssize_t (*const rd_ptr[TOTAL_ATTRS]) (struct device *dev,
                        struct device_attribute *devattr, char *buf) = {
                        show_label, show_crit_alarm, show_temp, show_tjmax,
                        show_ttarget };
        static const char *const suffixes[TOTAL_ATTRS] = {
                "label", "crit_alarm", "input", "crit", "max"
        };

        for (i = 0; i < tdata->attr_size; i++) {
                snprintf(tdata->attr_name[i], CORETEMP_NAME_LENGTH,
                         "temp%d_%s", attr_no, suffixes[i]);
                sysfs_attr_init(&tdata->sd_attrs[i].dev_attr.attr);
                tdata->sd_attrs[i].dev_attr.attr.name = tdata->attr_name[i];
                tdata->sd_attrs[i].dev_attr.attr.mode = 0444;
                tdata->sd_attrs[i].dev_attr.show = rd_ptr[i];
                tdata->sd_attrs[i].index = attr_no;
                tdata->attrs[i] = &tdata->sd_attrs[i].dev_attr.attr;
        }
        tdata->attr_group.attrs = tdata->attrs;
        return sysfs_create_group(&dev->kobj, &tdata->attr_group);
}


static int chk_ucode_version(unsigned int cpu)
{
        struct cpuinfo_x86 *c = &cpu_data(cpu);

        /*
         * Check if we have problem with errata AE18 of Core processors:
         * Readings might stop update when processor visited too deep sleep,
         * fixed for stepping D0 (6EC).
         */
        if (c->x86_model == 0xe && c->x86_stepping < 0xc && c->microcode < 0x39) {
                pr_err("Errata AE18 not fixed, update BIOS or microcode of the CPU!\n");
                return -ENODEV;
        }
        return 0;
}

static struct platform_device *coretemp_get_pdev(unsigned int cpu)
{
        int id = topology_logical_die_id(cpu);

        if (id >= 0 && id < max_zones)
                return zone_devices[id];
        return NULL;
}

static struct temp_data *init_temp_data(unsigned int cpu, int pkg_flag)
{
        struct temp_data *tdata;

        tdata = kzalloc(sizeof(struct temp_data), GFP_KERNEL);
        if (!tdata)
                return NULL;

        tdata->status_reg = pkg_flag ? MSR_IA32_PACKAGE_THERM_STATUS :
                                                        MSR_IA32_THERM_STATUS;
        tdata->is_pkg_data = pkg_flag;
        tdata->cpu = cpu;
        tdata->cpu_core_id = TO_CORE_ID(cpu);
        tdata->attr_size = MAX_CORE_ATTRS;
        mutex_init(&tdata->update_lock);
        return tdata;
}

static int create_core_data(struct platform_device *pdev, unsigned int cpu,
                            int pkg_flag)
{
        struct temp_data *tdata;
        struct platform_data *pdata = platform_get_drvdata(pdev);
        struct cpuinfo_x86 *c = &cpu_data(cpu);
        u32 eax, edx;
        int err, attr_no;

        /*
         * Find attr number for sysfs:
         * We map the attr number to core id of the CPU
         * The attr number is always core id + 2
         * The Pkgtemp will always show up as temp1_*, if available
         */
        attr_no = pkg_flag ? PKG_SYSFS_ATTR_NO : TO_ATTR_NO(cpu);

        if (attr_no > MAX_CORE_DATA - 1)
                return -ERANGE;

        tdata = init_temp_data(cpu, pkg_flag);
        if (!tdata)
                return -ENOMEM;

        /* Test if we can access the status register */
        err = rdmsr_safe_on_cpu(cpu, tdata->status_reg, &eax, &edx);
        if (err)
                goto exit_free;

        /* We can access status register. Get Critical Temperature */
        tdata->tjmax = get_tjmax(c, cpu, &pdev->dev);

        /*
         * Read the still undocumented bits 8:15 of IA32_TEMPERATURE_TARGET.
         * The target temperature is available on older CPUs but not in this
         * register. Atoms don't have the register at all.
         */
        if (c->x86_model > 0xe && c->x86_model != 0x1c) {
                err = rdmsr_safe_on_cpu(cpu, MSR_IA32_TEMPERATURE_TARGET,
                                        &eax, &edx);
                if (!err) {
                        tdata->ttarget
                          = tdata->tjmax - ((eax >> 8) & 0xff) * 1000;
                        tdata->attr_size++;
                }
        }

        pdata->core_data[attr_no] = tdata;

        /* Create sysfs interfaces */
        err = create_core_attrs(tdata, pdata->hwmon_dev, attr_no);
        if (err)
                goto exit_free;

        return 0;
exit_free:
        pdata->core_data[attr_no] = NULL;
        kfree(tdata);
        return err;
}

static void
coretemp_add_core(struct platform_device *pdev, unsigned int cpu, int pkg_flag)
{
        if (create_core_data(pdev, cpu, pkg_flag))
                dev_err(&pdev->dev, "Adding Core %u failed\n", cpu);
}

static void coretemp_remove_core(struct platform_data *pdata, int indx)
{
        struct temp_data *tdata = pdata->core_data[indx];

        /* Remove the sysfs attributes */
        sysfs_remove_group(&pdata->hwmon_dev->kobj, &tdata->attr_group);

        kfree(pdata->core_data[indx]);
        pdata->core_data[indx] = NULL;
}

static int coretemp_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct platform_data *pdata;

        /* Initialize the per-zone data structures */
        pdata = devm_kzalloc(dev, sizeof(struct platform_data), GFP_KERNEL);
        if (!pdata)
                return -ENOMEM;

        pdata->pkg_id = pdev->id;
        platform_set_drvdata(pdev, pdata);

        pdata->hwmon_dev = devm_hwmon_device_register_with_groups(dev, DRVNAME,
                                                                  pdata, NULL);
        return PTR_ERR_OR_ZERO(pdata->hwmon_dev);
}

static int coretemp_remove(struct platform_device *pdev)
{
        struct platform_data *pdata = platform_get_drvdata(pdev);
        int i;

        for (i = MAX_CORE_DATA - 1; i >= 0; --i)
                if (pdata->core_data[i])
                        coretemp_remove_core(pdata, i);

        return 0;
}

static struct platform_driver coretemp_driver = {
        .driver = {
                .name = DRVNAME,
        },
        .probe = coretemp_probe,
        .remove = coretemp_remove,
};

static struct platform_device *coretemp_device_add(unsigned int cpu)
{
        int err, zoneid = topology_logical_die_id(cpu);
        struct platform_device *pdev;

        if (zoneid < 0)
                return ERR_PTR(-ENOMEM);

        pdev = platform_device_alloc(DRVNAME, zoneid);
        if (!pdev)
                return ERR_PTR(-ENOMEM);

        err = platform_device_add(pdev);
        if (err) {
                platform_device_put(pdev);
                return ERR_PTR(err);
        }

        zone_devices[zoneid] = pdev;
        return pdev;
}

static int coretemp_cpu_online(unsigned int cpu)
{
        struct platform_device *pdev = coretemp_get_pdev(cpu);
        struct cpuinfo_x86 *c = &cpu_data(cpu);
        struct platform_data *pdata;

        /*
         * Don't execute this on resume as the offline callback did
         * not get executed on suspend.
         */
        if (cpuhp_tasks_frozen)
                return 0;

        /*
         * CPUID.06H.EAX[0] indicates whether the CPU has thermal
         * sensors. We check this bit only, all the early CPUs
         * without thermal sensors will be filtered out.
         */
        if (!cpu_has(c, X86_FEATURE_DTHERM))
                return -ENODEV;

        if (!pdev) {
                /* Check the microcode version of the CPU */
                if (chk_ucode_version(cpu))
                        return -EINVAL;

                /*
                 * Alright, we have DTS support.
                 * We are bringing the _first_ core in this pkg
                 * online. So, initialize per-pkg data structures and
                 * then bring this core online.
                 */
                pdev = coretemp_device_add(cpu);
                if (IS_ERR(pdev))
                        return PTR_ERR(pdev);

                /*
                 * Check whether pkgtemp support is available.
                 * If so, add interfaces for pkgtemp.
                 */
                if (cpu_has(c, X86_FEATURE_PTS))
                        coretemp_add_core(pdev, cpu, 1);
        }

        pdata = platform_get_drvdata(pdev);
        /*
         * Check whether a thread sibling is already online. If not add the
         * interface for this CPU core.
         */
        if (!cpumask_intersects(&pdata->cpumask, topology_sibling_cpumask(cpu)))
                coretemp_add_core(pdev, cpu, 0);

        cpumask_set_cpu(cpu, &pdata->cpumask);
        return 0;
}

static int coretemp_cpu_offline(unsigned int cpu)
{
        struct platform_device *pdev = coretemp_get_pdev(cpu);
        struct platform_data *pd;
        struct temp_data *tdata;
        int indx, target;

        /*
         * Don't execute this on suspend as the device remove locks
         * up the machine.
         */
        if (cpuhp_tasks_frozen)
                return 0;

        /* If the physical CPU device does not exist, just return */
        if (!pdev)
                return 0;

        /* The core id is too big, just return */
        indx = TO_ATTR_NO(cpu);
        if (indx > MAX_CORE_DATA - 1)
                return 0;

        pd = platform_get_drvdata(pdev);
        tdata = pd->core_data[indx];

        cpumask_clear_cpu(cpu, &pd->cpumask);

        /*
         * If this is the last thread sibling, remove the CPU core
         * interface, If there is still a sibling online, transfer the
         * target cpu of that core interface to it.
         */
        target = cpumask_any_and(&pd->cpumask, topology_sibling_cpumask(cpu));
        if (target >= nr_cpu_ids) {
                coretemp_remove_core(pd, indx);
        } else if (tdata && tdata->cpu == cpu) {
                mutex_lock(&tdata->update_lock);
                tdata->cpu = target;
                mutex_unlock(&tdata->update_lock);
        }

        /*
         * If all cores in this pkg are offline, remove the device. This
         * will invoke the platform driver remove function, which cleans up
         * the rest.
         */
        if (cpumask_empty(&pd->cpumask)) {
                zone_devices[topology_logical_die_id(cpu)] = NULL;
                platform_device_unregister(pdev);
                return 0;
        }

        /*
         * Check whether this core is the target for the package
         * interface. We need to assign it to some other cpu.
         */
        tdata = pd->core_data[PKG_SYSFS_ATTR_NO];
        if (tdata && tdata->cpu == cpu) {
                target = cpumask_first(&pd->cpumask);
                mutex_lock(&tdata->update_lock);
                tdata->cpu = target;
                mutex_unlock(&tdata->update_lock);
        }
        return 0;
}
static const struct x86_cpu_id __initconst coretemp_ids[] = {
        X86_MATCH_VENDOR_FEATURE(INTEL, X86_FEATURE_DTHERM, NULL),
        {}
};
MODULE_DEVICE_TABLE(x86cpu, coretemp_ids);

static enum cpuhp_state coretemp_hp_online;

static int __init coretemp_init(void)
{
        int err;

        /*
         * CPUID.06H.EAX[0] indicates whether the CPU has thermal
         * sensors. We check this bit only, all the early CPUs
         * without thermal sensors will be filtered out.
         */
        if (!x86_match_cpu(coretemp_ids))
                return -ENODEV;

        max_zones = topology_max_packages() * topology_max_die_per_package();
        zone_devices = kcalloc(max_zones, sizeof(struct platform_device *),
                              GFP_KERNEL);
        if (!zone_devices)
                return -ENOMEM;

        err = platform_driver_register(&coretemp_driver);
        if (err)
                goto outzone;

        err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "hwmon/coretemp:online",
                                coretemp_cpu_online, coretemp_cpu_offline);
        if (err < 0)
                goto outdrv;
        coretemp_hp_online = err;
        return 0;

outdrv:
        platform_driver_unregister(&coretemp_driver);
outzone:
        kfree(zone_devices);
        return err;
}
module_init(coretemp_init)

static void __exit coretemp_exit(void)
{
        cpuhp_remove_state(coretemp_hp_online);
        platform_driver_unregister(&coretemp_driver);
        kfree(zone_devices);
}
module_exit(coretemp_exit)

MODULE_AUTHOR("Rudolf Marek <r.marek@assembler.cz>");
MODULE_DESCRIPTION("Intel Core temperature monitor");
MODULE_LICENSE("GPL");