linux/drivers/hwmon/coretemp.c

// 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");