PowerCap: Introduce Intel RAPL power capping driver

The Intel Running Average Power Limit (RAPL) technology provides platform
software with the ability to monitor, control, and get notifications on
power usage.

This feature is present in all Sandy Bridge and later Intel processors.
Newer models allow more fine grained controls to be applied.  In RAPL,
power control is divided into domains, which include package, DRAM
controller, CPU core (Power Plane 0), graphics uncore (power plane 1), etc.

The purpose of this driver is to expose the RAPL settings to userspace.
Overall, RAPL fits in the new powercap class driver in that platform
level power capping controls are exposed via this generic interface.

This driver is based on an earlier patch from Zhang Rui.

However, while the previous work was mainly focused on thermal monitoring
the focus here is on the usability from user space perspective.

References: https://lkml.org/lkml/2011/5/26/93
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 1395 insertions, 0 deletions

diff --git a/drivers/powercap/intel_rapl.c b/drivers/powercap/intel_rapl.c
new file mode 100644
index 000000000000..2a786c504460
--- /dev/null
+++ b/drivers/powercap/intel_rapl.c
@@ -0,0 +1,1395 @@
+/*
+ * Intel Running Average Power Limit (RAPL) Driver
+ * Copyright (c) 2013, Intel Corporation.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc.
+ *
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/list.h>
+#include <linux/types.h>
+#include <linux/device.h>
+#include <linux/slab.h>
+#include <linux/log2.h>
+#include <linux/bitmap.h>
+#include <linux/delay.h>
+#include <linux/sysfs.h>
+#include <linux/cpu.h>
+#include <linux/powercap.h>
+
+#include <asm/processor.h>
+#include <asm/cpu_device_id.h>
+
+/* bitmasks for RAPL MSRs, used by primitive access functions */
+#define ENERGY_STATUS_MASK      0xffffffff
+
+#define POWER_LIMIT1_MASK       0x7FFF
+#define POWER_LIMIT1_ENABLE     BIT(15)
+#define POWER_LIMIT1_CLAMP      BIT(16)
+
+#define POWER_LIMIT2_MASK       (0x7FFFULL<<32)
+#define POWER_LIMIT2_ENABLE     BIT_ULL(47)
+#define POWER_LIMIT2_CLAMP      BIT_ULL(48)
+#define POWER_PACKAGE_LOCK      BIT_ULL(63)
+#define POWER_PP_LOCK           BIT(31)
+
+#define TIME_WINDOW1_MASK       (0x7FULL<<17)
+#define TIME_WINDOW2_MASK       (0x7FULL<<49)
+
+#define POWER_UNIT_OFFSET	0
+#define POWER_UNIT_MASK		0x0F
+
+#define ENERGY_UNIT_OFFSET	0x08
+#define ENERGY_UNIT_MASK	0x1F00
+
+#define TIME_UNIT_OFFSET	0x10
+#define TIME_UNIT_MASK		0xF0000
+
+#define POWER_INFO_MAX_MASK     (0x7fffULL<<32)
+#define POWER_INFO_MIN_MASK     (0x7fffULL<<16)
+#define POWER_INFO_MAX_TIME_WIN_MASK     (0x3fULL<<48)
+#define POWER_INFO_THERMAL_SPEC_MASK     0x7fff
+
+#define PERF_STATUS_THROTTLE_TIME_MASK 0xffffffff
+#define PP_POLICY_MASK         0x1F
+
+/* Non HW constants */
+#define RAPL_PRIMITIVE_DERIVED       BIT(1) /* not from raw data */
+#define RAPL_PRIMITIVE_DUMMY         BIT(2)
+
+/* scale RAPL units to avoid floating point math inside kernel */
+#define POWER_UNIT_SCALE     (1000000)
+#define ENERGY_UNIT_SCALE    (1000000)
+#define TIME_UNIT_SCALE      (1000000)
+
+#define TIME_WINDOW_MAX_MSEC 40000
+#define TIME_WINDOW_MIN_MSEC 250
+
+enum unit_type {
+	ARBITRARY_UNIT, /* no translation */
+	POWER_UNIT,
+	ENERGY_UNIT,
+	TIME_UNIT,
+};
+
+enum rapl_domain_type {
+	RAPL_DOMAIN_PACKAGE, /* entire package/socket */
+	RAPL_DOMAIN_PP0, /* core power plane */
+	RAPL_DOMAIN_PP1, /* graphics uncore */
+	RAPL_DOMAIN_DRAM,/* DRAM control_type */
+	RAPL_DOMAIN_MAX,
+};
+
+enum rapl_domain_msr_id {
+	RAPL_DOMAIN_MSR_LIMIT,
+	RAPL_DOMAIN_MSR_STATUS,
+	RAPL_DOMAIN_MSR_PERF,
+	RAPL_DOMAIN_MSR_POLICY,
+	RAPL_DOMAIN_MSR_INFO,
+	RAPL_DOMAIN_MSR_MAX,
+};
+
+/* per domain data, some are optional */
+enum rapl_primitives {
+	ENERGY_COUNTER,
+	POWER_LIMIT1,
+	POWER_LIMIT2,
+	FW_LOCK,
+
+	PL1_ENABLE,  /* power limit 1, aka long term */
+	PL1_CLAMP,   /* allow frequency to go below OS request */
+	PL2_ENABLE,  /* power limit 2, aka short term, instantaneous */
+	PL2_CLAMP,
+
+	TIME_WINDOW1, /* long term */
+	TIME_WINDOW2, /* short term */
+	THERMAL_SPEC_POWER,
+	MAX_POWER,
+
+	MIN_POWER,
+	MAX_TIME_WINDOW,
+	THROTTLED_TIME,
+	PRIORITY_LEVEL,
+
+	/* below are not raw primitive data */
+	AVERAGE_POWER,
+	NR_RAPL_PRIMITIVES,
+};
+
+#define NR_RAW_PRIMITIVES (NR_RAPL_PRIMITIVES - 2)
+
+/* Can be expanded to include events, etc.*/
+struct rapl_domain_data {
+	u64 primitives[NR_RAPL_PRIMITIVES];
+	unsigned long timestamp;
+};
+
+
+#define	DOMAIN_STATE_INACTIVE           BIT(0)
+#define	DOMAIN_STATE_POWER_LIMIT_SET    BIT(1)
+#define DOMAIN_STATE_BIOS_LOCKED        BIT(2)
+
+#define NR_POWER_LIMITS (2)
+struct rapl_power_limit {
+	struct powercap_zone_constraint *constraint;
+	int prim_id; /* primitive ID used to enable */
+	struct rapl_domain *domain;
+	const char *name;
+};
+
+static const char pl1_name[] = "long_term";
+static const char pl2_name[] = "short_term";
+
+struct rapl_domain {
+	const char *name;
+	enum rapl_domain_type id;
+	int msrs[RAPL_DOMAIN_MSR_MAX];
+	struct powercap_zone power_zone;
+	struct rapl_domain_data rdd;
+	struct rapl_power_limit rpl[NR_POWER_LIMITS];
+	u64 attr_map; /* track capabilities */
+	unsigned int state;
+	int package_id;
+};
+#define power_zone_to_rapl_domain(_zone) \
+	container_of(_zone, struct rapl_domain, power_zone)
+
+
+/* Each physical package contains multiple domains, these are the common
+ * data across RAPL domains within a package.
+ */
+struct rapl_package {
+	unsigned int id; /* physical package/socket id */
+	unsigned int nr_domains;
+	unsigned long domain_map; /* bit map of active domains */
+	unsigned int power_unit_divisor;
+	unsigned int energy_unit_divisor;
+	unsigned int time_unit_divisor;
+	struct rapl_domain *domains; /* array of domains, sized at runtime */
+	struct powercap_zone *power_zone; /* keep track of parent zone */
+	int nr_cpus; /* active cpus on the package, topology info is lost during
+		      * cpu hotplug. so we have to track ourselves.
+		      */
+	unsigned long power_limit_irq; /* keep track of package power limit
+					* notify interrupt enable status.
+					*/
+	struct list_head plist;
+};
+#define PACKAGE_PLN_INT_SAVED   BIT(0)
+#define MAX_PRIM_NAME (32)
+
+/* per domain data. used to describe individual knobs such that access function
+ * can be consolidated into one instead of many inline functions.
+ */
+struct rapl_primitive_info {
+	const char *name;
+	u64 mask;
+	int shift;
+	enum rapl_domain_msr_id id;
+	enum unit_type unit;
+	u32 flag;
+};
+
+#define PRIMITIVE_INFO_INIT(p, m, s, i, u, f) {	\
+		.name = #p,			\
+		.mask = m,			\
+		.shift = s,			\
+		.id = i,			\
+		.unit = u,			\
+		.flag = f			\
+	}
+
+static void rapl_init_domains(struct rapl_package *rp);
+static int rapl_read_data_raw(struct rapl_domain *rd,
+			enum rapl_primitives prim,
+			bool xlate, u64 *data);
+static int rapl_write_data_raw(struct rapl_domain *rd,
+			enum rapl_primitives prim,
+			unsigned long long value);
+static u64 rapl_unit_xlate(int package, enum unit_type type, u64 value,
+			int to_raw);
+static void package_power_limit_irq_save(int package_id);
+
+static LIST_HEAD(rapl_packages); /* guarded by CPU hotplug lock */
+
+static const char * const rapl_domain_names[] = {
+	"package",
+	"core",
+	"uncore",
+	"dram",
+};
+
+static struct powercap_control_type *control_type; /* PowerCap Controller */
+
+/* caller to ensure CPU hotplug lock is held */
+static struct rapl_package *find_package_by_id(int id)
+{
+	struct rapl_package *rp;
+
+	list_for_each_entry(rp, &rapl_packages, plist) {
+		if (rp->id == id)
+			return rp;
+	}
+
+	return NULL;
+}
+
+/* caller to ensure CPU hotplug lock is held */
+static int find_active_cpu_on_package(int package_id)
+{
+	int i;
+
+	for_each_online_cpu(i) {
+		if (topology_physical_package_id(i) == package_id)
+			return i;
+	}
+	/* all CPUs on this package are offline */
+
+	return -ENODEV;
+}
+
+/* caller must hold cpu hotplug lock */
+static void rapl_cleanup_data(void)
+{
+	struct rapl_package *p, *tmp;
+
+	list_for_each_entry_safe(p, tmp, &rapl_packages, plist) {
+		kfree(p->domains);
+		list_del(&p->plist);
+		kfree(p);
+	}
+}
+
+static int get_energy_counter(struct powercap_zone *power_zone, u64 *energy_raw)
+{
+	struct rapl_domain *rd;
+	u64 energy_now;
+
+	/* prevent CPU hotplug, make sure the RAPL domain does not go
+	 * away while reading the counter.
+	 */
+	get_online_cpus();
+	rd = power_zone_to_rapl_domain(power_zone);
+
+	if (!rapl_read_data_raw(rd, ENERGY_COUNTER, true, &energy_now)) {
+		*energy_raw = energy_now;
+		put_online_cpus();
+
+		return 0;
+	}
+	put_online_cpus();
+
+	return -EIO;
+}
+
+static int get_max_energy_counter(struct powercap_zone *pcd_dev, u64 *energy)
+{
+	*energy = rapl_unit_xlate(0, ENERGY_UNIT, ENERGY_STATUS_MASK, 0);
+	return 0;
+}
+
+static int release_zone(struct powercap_zone *power_zone)
+{
+	struct rapl_domain *rd = power_zone_to_rapl_domain(power_zone);
+	struct rapl_package *rp;
+
+	/* package zone is the last zone of a package, we can free
+	 * memory here since all children has been unregistered.
+	 */
+	if (rd->id == RAPL_DOMAIN_PACKAGE) {
+		rp = find_package_by_id(rd->package_id);
+		if (!rp) {
+			dev_warn(&power_zone->dev, "no package id %s\n",
+				rd->name);
+			return -ENODEV;
+		}
+		kfree(rd);
+		rp->domains = NULL;
+	}
+
+	return 0;
+
+}
+
+static int find_nr_power_limit(struct rapl_domain *rd)
+{
+	int i;
+
+	for (i = 0; i < NR_POWER_LIMITS; i++) {
+		if (rd->rpl[i].name == NULL)
+			break;
+	}
+
+	return i;
+}
+
+static int set_domain_enable(struct powercap_zone *power_zone, bool mode)
+{
+	struct rapl_domain *rd = power_zone_to_rapl_domain(power_zone);
+	int nr_powerlimit;
+
+	if (rd->state & DOMAIN_STATE_BIOS_LOCKED)
+		return -EACCES;
+	get_online_cpus();
+	nr_powerlimit = find_nr_power_limit(rd);
+	/* here we activate/deactivate the hardware for power limiting */
+	rapl_write_data_raw(rd, PL1_ENABLE, mode);
+	/* always enable clamp such that p-state can go below OS requested
+	 * range. power capping priority over guranteed frequency.
+	 */
+	rapl_write_data_raw(rd, PL1_CLAMP, mode);
+	/* some domains have pl2 */
+	if (nr_powerlimit > 1) {
+		rapl_write_data_raw(rd, PL2_ENABLE, mode);
+		rapl_write_data_raw(rd, PL2_CLAMP, mode);
+	}
+	put_online_cpus();
+
+	return 0;
+}
+
+static int get_domain_enable(struct powercap_zone *power_zone, bool *mode)
+{
+	struct rapl_domain *rd = power_zone_to_rapl_domain(power_zone);
+	u64 val;
+
+	if (rd->state & DOMAIN_STATE_BIOS_LOCKED) {
+		*mode = false;
+		return 0;
+	}
+	get_online_cpus();
+	if (rapl_read_data_raw(rd, PL1_ENABLE, true, &val)) {
+		put_online_cpus();
+		return -EIO;
+	}
+	*mode = val;
+	put_online_cpus();
+
+	return 0;
+}
+
+/* per RAPL domain ops, in the order of rapl_domain_type */
+static struct powercap_zone_ops zone_ops[] = {
+	/* RAPL_DOMAIN_PACKAGE */
+	{
+		.get_energy_uj = get_energy_counter,
+		.get_max_energy_range_uj = get_max_energy_counter,
+		.release = release_zone,
+		.set_enable = set_domain_enable,
+		.get_enable = get_domain_enable,
+	},
+	/* RAPL_DOMAIN_PP0 */
+	{
+		.get_energy_uj = get_energy_counter,
+		.get_max_energy_range_uj = get_max_energy_counter,
+		.release = release_zone,
+		.set_enable = set_domain_enable,
+		.get_enable = get_domain_enable,
+	},
+	/* RAPL_DOMAIN_PP1 */
+	{
+		.get_energy_uj = get_energy_counter,
+		.get_max_energy_range_uj = get_max_energy_counter,
+		.release = release_zone,
+		.set_enable = set_domain_enable,
+		.get_enable = get_domain_enable,
+	},
+	/* RAPL_DOMAIN_DRAM */
+	{
+		.get_energy_uj = get_energy_counter,
+		.get_max_energy_range_uj = get_max_energy_counter,
+		.release = release_zone,
+		.set_enable = set_domain_enable,
+		.get_enable = get_domain_enable,
+	},
+};
+
+static int set_power_limit(struct powercap_zone *power_zone, int id,
+			u64 power_limit)
+{
+	struct rapl_domain *rd;
+	struct rapl_package *rp;
+	int ret = 0;
+
+	get_online_cpus();
+	rd = power_zone_to_rapl_domain(power_zone);
+	rp = find_package_by_id(rd->package_id);
+	if (!rp) {
+		ret = -ENODEV;
+		goto set_exit;
+	}
+
+	if (rd->state & DOMAIN_STATE_BIOS_LOCKED) {
+		dev_warn(&power_zone->dev, "%s locked by BIOS, monitoring only\n",
+			rd->name);
+		ret = -EACCES;
+		goto set_exit;
+	}
+
+	switch (rd->rpl[id].prim_id) {
+	case PL1_ENABLE:
+		rapl_write_data_raw(rd, POWER_LIMIT1, power_limit);
+		break;
+	case PL2_ENABLE:
+		rapl_write_data_raw(rd, POWER_LIMIT2, power_limit);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+	if (!ret)
+		package_power_limit_irq_save(rd->package_id);
+set_exit:
+	put_online_cpus();
+	return ret;
+}
+
+static int get_current_power_limit(struct powercap_zone *power_zone, int id,
+					u64 *data)
+{
+	struct rapl_domain *rd;
+	u64 val;
+	int prim;
+	int ret = 0;
+
+	get_online_cpus();
+	rd = power_zone_to_rapl_domain(power_zone);
+	switch (rd->rpl[id].prim_id) {
+	case PL1_ENABLE:
+		prim = POWER_LIMIT1;
+		break;
+	case PL2_ENABLE:
+		prim = POWER_LIMIT2;
+		break;
+	default:
+		put_online_cpus();
+		return -EINVAL;
+	}
+	if (rapl_read_data_raw(rd, prim, true, &val))
+		ret = -EIO;
+	else
+		*data = val;
+
+	put_online_cpus();
+
+	return ret;
+}
+
+static int set_time_window(struct powercap_zone *power_zone, int id,
+								u64 window)
+{
+	struct rapl_domain *rd;
+	int ret = 0;
+
+	get_online_cpus();
+	rd = power_zone_to_rapl_domain(power_zone);
+	switch (rd->rpl[id].prim_id) {
+	case PL1_ENABLE:
+		rapl_write_data_raw(rd, TIME_WINDOW1, window);
+		break;
+	case PL2_ENABLE:
+		rapl_write_data_raw(rd, TIME_WINDOW2, window);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+	put_online_cpus();
+	return ret;
+}
+
+static int get_time_window(struct powercap_zone *power_zone, int id, u64 *data)
+{
+	struct rapl_domain *rd;
+	u64 val;
+	int ret = 0;
+
+	get_online_cpus();
+	rd = power_zone_to_rapl_domain(power_zone);
+	switch (rd->rpl[id].prim_id) {
+	case PL1_ENABLE:
+		ret = rapl_read_data_raw(rd, TIME_WINDOW1, true, &val);
+		break;
+	case PL2_ENABLE:
+		ret = rapl_read_data_raw(rd, TIME_WINDOW2, true, &val);
+		break;
+	default:
+		put_online_cpus();
+		return -EINVAL;
+	}
+	if (!ret)
+		*data = val;
+	put_online_cpus();
+
+	return ret;
+}
+
+static const char *get_constraint_name(struct powercap_zone *power_zone, int id)
+{
+	struct rapl_power_limit *rpl;
+	struct rapl_domain *rd;
+
+	rd = power_zone_to_rapl_domain(power_zone);
+	rpl = (struct rapl_power_limit *) &rd->rpl[id];
+
+	return rpl->name;
+}
+
+
+static int get_max_power(struct powercap_zone *power_zone, int id,
+					u64 *data)
+{
+	struct rapl_domain *rd;
+	u64 val;
+	int prim;
+	int ret = 0;
+
+	get_online_cpus();
+	rd = power_zone_to_rapl_domain(power_zone);
+	switch (rd->rpl[id].prim_id) {
+	case PL1_ENABLE:
+		prim = THERMAL_SPEC_POWER;
+		break;
+	case PL2_ENABLE:
+		prim = MAX_POWER;
+		break;
+	default:
+		put_online_cpus();
+		return -EINVAL;
+	}
+	if (rapl_read_data_raw(rd, prim, true, &val))
+		ret = -EIO;
+	else
+		*data = val;
+
+	put_online_cpus();
+
+	return ret;
+}
+
+static struct powercap_zone_constraint_ops constraint_ops = {
+	.set_power_limit_uw = set_power_limit,
+	.get_power_limit_uw = get_current_power_limit,
+	.set_time_window_us = set_time_window,
+	.get_time_window_us = get_time_window,
+	.get_max_power_uw = get_max_power,
+	.get_name = get_constraint_name,
+};
+
+/* called after domain detection and package level data are set */
+static void rapl_init_domains(struct rapl_package *rp)
+{
+	int i;
+	struct rapl_domain *rd = rp->domains;
+
+	for (i = 0; i < RAPL_DOMAIN_MAX; i++) {
+		unsigned int mask = rp->domain_map & (1 << i);
+		switch (mask) {
+		case BIT(RAPL_DOMAIN_PACKAGE):
+			rd->name = rapl_domain_names[RAPL_DOMAIN_PACKAGE];
+			rd->id = RAPL_DOMAIN_PACKAGE;
+			rd->msrs[0] = MSR_PKG_POWER_LIMIT;
+			rd->msrs[1] = MSR_PKG_ENERGY_STATUS;
+			rd->msrs[2] = MSR_PKG_PERF_STATUS;
+			rd->msrs[3] = 0;
+			rd->msrs[4] = MSR_PKG_POWER_INFO;
+			rd->rpl[0].prim_id = PL1_ENABLE;
+			rd->rpl[0].name = pl1_name;
+			rd->rpl[1].prim_id = PL2_ENABLE;
+			rd->rpl[1].name = pl2_name;
+			break;
+		case BIT(RAPL_DOMAIN_PP0):
+			rd->name = rapl_domain_names[RAPL_DOMAIN_PP0];
+			rd->id = RAPL_DOMAIN_PP0;
+			rd->msrs[0] = MSR_PP0_POWER_LIMIT;
+			rd->msrs[1] = MSR_PP0_ENERGY_STATUS;
+			rd->msrs[2] = 0;
+			rd->msrs[3] = MSR_PP0_POLICY;
+			rd->msrs[4] = 0;
+			rd->rpl[0].prim_id = PL1_ENABLE;
+			rd->rpl[0].name = pl1_name;
+			break;
+		case BIT(RAPL_DOMAIN_PP1):
+			rd->name = rapl_domain_names[RAPL_DOMAIN_PP1];
+			rd->id = RAPL_DOMAIN_PP1;
+			rd->msrs[0] = MSR_PP1_POWER_LIMIT;
+			rd->msrs[1] = MSR_PP1_ENERGY_STATUS;
+			rd->msrs[2] = 0;
+			rd->msrs[3] = MSR_PP1_POLICY;
+			rd->msrs[4] = 0;
+			rd->rpl[0].prim_id = PL1_ENABLE;
+			rd->rpl[0].name = pl1_name;
+			break;
+		case BIT(RAPL_DOMAIN_DRAM):
+			rd->name = rapl_domain_names[RAPL_DOMAIN_DRAM];
+			rd->id = RAPL_DOMAIN_DRAM;
+			rd->msrs[0] = MSR_DRAM_POWER_LIMIT;
+			rd->msrs[1] = MSR_DRAM_ENERGY_STATUS;
+			rd->msrs[2] = MSR_DRAM_PERF_STATUS;
+			rd->msrs[3] = 0;
+			rd->msrs[4] = MSR_DRAM_POWER_INFO;
+			rd->rpl[0].prim_id = PL1_ENABLE;
+			rd->rpl[0].name = pl1_name;
+			break;
+		}
+		if (mask) {
+			rd->package_id = rp->id;
+			rd++;
+		}
+	}
+}
+
+static u64 rapl_unit_xlate(int package, enum unit_type type, u64 value,
+			int to_raw)
+{
+	u64 divisor = 1;
+	int scale = 1; /* scale to user friendly data without floating point */
+	u64 f, y; /* fraction and exp. used for time unit */
+	struct rapl_package *rp;
+
+	rp = find_package_by_id(package);
+	if (!rp)
+		return value;
+
+	switch (type) {
+	case POWER_UNIT:
+		divisor = rp->power_unit_divisor;
+		scale = POWER_UNIT_SCALE;
+		break;
+	case ENERGY_UNIT:
+		scale = ENERGY_UNIT_SCALE;
+		divisor = rp->energy_unit_divisor;
+		break;
+	case TIME_UNIT:
+		divisor = rp->time_unit_divisor;
+		scale = TIME_UNIT_SCALE;
+		/* special processing based on 2^Y*(1+F)/4 = val/divisor, refer
+		 * to Intel Software Developer's manual Vol. 3a, CH 14.7.4.
+		 */
+		if (!to_raw) {
+			f = (value & 0x60) >> 5;
+			y = value & 0x1f;
+			value = (1 << y) * (4 + f) * scale / 4;
+			return div64_u64(value, divisor);
+		} else {
+			do_div(value, scale);
+			value *= divisor;
+			y = ilog2(value);
+			f = div64_u64(4 * (value - (1 << y)), 1 << y);
+			value = (y & 0x1f) | ((f & 0x3) << 5);
+			return value;
+		}
+		break;
+	case ARBITRARY_UNIT:
+	default:
+		return value;
+	};
+
+	if (to_raw)
+		return div64_u64(value * divisor, scale);
+	else
+		return div64_u64(value * scale, divisor);
+}
+
+/* in the order of enum rapl_primitives */
+static struct rapl_primitive_info rpi[] = {
+	/* name, mask, shift, msr index, unit divisor */
+	PRIMITIVE_INFO_INIT(ENERGY_COUNTER, ENERGY_STATUS_MASK, 0,
+				RAPL_DOMAIN_MSR_STATUS, ENERGY_UNIT, 0),
+	PRIMITIVE_INFO_INIT(POWER_LIMIT1, POWER_LIMIT1_MASK, 0,
+				RAPL_DOMAIN_MSR_LIMIT, POWER_UNIT, 0),
+	PRIMITIVE_INFO_INIT(POWER_LIMIT2, POWER_LIMIT2_MASK, 32,
+				RAPL_DOMAIN_MSR_LIMIT, POWER_UNIT, 0),
+	PRIMITIVE_INFO_INIT(FW_LOCK, POWER_PP_LOCK, 31,
+				RAPL_DOMAIN_MSR_LIMIT, ARBITRARY_UNIT, 0),
+	PRIMITIVE_INFO_INIT(PL1_ENABLE, POWER_LIMIT1_ENABLE, 15,
+				RAPL_DOMAIN_MSR_LIMIT, ARBITRARY_UNIT, 0),
+	PRIMITIVE_INFO_INIT(PL1_CLAMP, POWER_LIMIT1_CLAMP, 16,
+				RAPL_DOMAIN_MSR_LIMIT, ARBITRARY_UNIT, 0),
+	PRIMITIVE_INFO_INIT(PL2_ENABLE, POWER_LIMIT2_ENABLE, 47,
+				RAPL_DOMAIN_MSR_LIMIT, ARBITRARY_UNIT, 0),
+	PRIMITIVE_INFO_INIT(PL2_CLAMP, POWER_LIMIT2_CLAMP, 48,
+				RAPL_DOMAIN_MSR_LIMIT, ARBITRARY_UNIT, 0),
+	PRIMITIVE_INFO_INIT(TIME_WINDOW1, TIME_WINDOW1_MASK, 17,
+				RAPL_DOMAIN_MSR_LIMIT, TIME_UNIT, 0),
+	PRIMITIVE_INFO_INIT(TIME_WINDOW2, TIME_WINDOW2_MASK, 49,
+				RAPL_DOMAIN_MSR_LIMIT, TIME_UNIT, 0),
+	PRIMITIVE_INFO_INIT(THERMAL_SPEC_POWER, POWER_INFO_THERMAL_SPEC_MASK,
+				0, RAPL_DOMAIN_MSR_INFO, POWER_UNIT, 0),
+	PRIMITIVE_INFO_INIT(MAX_POWER, POWER_INFO_MAX_MASK, 32,
+				RAPL_DOMAIN_MSR_INFO, POWER_UNIT, 0),
+	PRIMITIVE_INFO_INIT(MIN_POWER, POWER_INFO_MIN_MASK, 16,
+				RAPL_DOMAIN_MSR_INFO, POWER_UNIT, 0),
+	PRIMITIVE_INFO_INIT(MAX_TIME_WINDOW, POWER_INFO_MAX_TIME_WIN_MASK, 48,
+				RAPL_DOMAIN_MSR_INFO, TIME_UNIT, 0),
+	PRIMITIVE_INFO_INIT(THROTTLED_TIME, PERF_STATUS_THROTTLE_TIME_MASK, 0,
+				RAPL_DOMAIN_MSR_PERF, TIME_UNIT, 0),
+	PRIMITIVE_INFO_INIT(PRIORITY_LEVEL, PP_POLICY_MASK, 0,
+				RAPL_DOMAIN_MSR_POLICY, ARBITRARY_UNIT, 0),
+	/* non-hardware */
+	PRIMITIVE_INFO_INIT(AVERAGE_POWER, 0, 0, 0, POWER_UNIT,
+				RAPL_PRIMITIVE_DERIVED),
+	{NULL, 0, 0, 0},
+};
+
+/* Read primitive data based on its related struct rapl_primitive_info.
+ * if xlate flag is set, return translated data based on data units, i.e.
+ * time, energy, and power.
+ * RAPL MSRs are non-architectual and are laid out not consistently across
+ * domains. Here we use primitive info to allow writing consolidated access
+ * functions.
+ * For a given primitive, it is processed by MSR mask and shift. Unit conversion
+ * is pre-assigned based on RAPL unit MSRs read at init time.
+ * 63-------------------------- 31--------------------------- 0
+ * |                           xxxxx (mask)                   |
+ * |                                |<- shift ----------------|
+ * 63-------------------------- 31--------------------------- 0
+ */
+static int rapl_read_data_raw(struct rapl_domain *rd,
+			enum rapl_primitives prim,
+			bool xlate, u64 *data)
+{
+	u64 value, final;
+	u32 msr;
+	struct rapl_primitive_info *rp = &rpi[prim];
+	int cpu;
+
+	if (!rp->name || rp->flag & RAPL_PRIMITIVE_DUMMY)
+		return -EINVAL;
+
+	msr = rd->msrs[rp->id];
+	if (!msr)
+		return -EINVAL;
+	/* use physical package id to look up active cpus */
+	cpu = find_active_cpu_on_package(rd->package_id);
+	if (cpu < 0)
+		return cpu;
+
+	/* special-case package domain, which uses a different bit*/
+	if (prim == FW_LOCK && rd->id == RAPL_DOMAIN_PACKAGE) {
+		rp->mask = POWER_PACKAGE_LOCK;
+		rp->shift = 63;
+	}
+	/* non-hardware data are collected by the polling thread */
+	if (rp->flag & RAPL_PRIMITIVE_DERIVED) {
+		*data = rd->rdd.primitives[prim];
+		return 0;
+	}
+
+	if (rdmsrl_safe_on_cpu(cpu, msr, &value)) {
+		pr_debug("failed to read msr 0x%x on cpu %d\n", msr, cpu);
+		return -EIO;
+	}
+
+	final = value & rp->mask;
+	final = final >> rp->shift;
+	if (xlate)
+		*data = rapl_unit_xlate(rd->package_id, rp->unit, final, 0);
+	else
+		*data = final;
+
+	return 0;
+}
+
+/* Similar use of primitive info in the read counterpart */
+static int rapl_write_data_raw(struct rapl_domain *rd,
+			enum rapl_primitives prim,
+			unsigned long long value)
+{
+	u64 msr_val;
+	u32 msr;
+	struct rapl_primitive_info *rp = &rpi[prim];
+	int cpu;
+
+	cpu = find_active_cpu_on_package(rd->package_id);
+	if (cpu < 0)
+		return cpu;
+	msr = rd->msrs[rp->id];
+	if (rdmsrl_safe_on_cpu(cpu, msr, &msr_val)) {
+		dev_dbg(&rd->power_zone.dev,
+			"failed to read msr 0x%x on cpu %d\n", msr, cpu);
+		return -EIO;
+	}
+	value = rapl_unit_xlate(rd->package_id, rp->unit, value, 1);
+	msr_val &= ~rp->mask;
+	msr_val |= value << rp->shift;
+	if (wrmsrl_safe_on_cpu(cpu, msr, msr_val)) {
+		dev_dbg(&rd->power_zone.dev,
+			"failed to write msr 0x%x on cpu %d\n", msr, cpu);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static int rapl_check_unit(struct rapl_package *rp, int cpu)
+{
+	u64 msr_val;
+	u32 value;
+
+	if (rdmsrl_safe_on_cpu(cpu, MSR_RAPL_POWER_UNIT, &msr_val)) {
+		pr_err("Failed to read power unit MSR 0x%x on CPU %d, exit.\n",
+			MSR_RAPL_POWER_UNIT, cpu);
+		return -ENODEV;
+	}
+
+	/* Raw RAPL data stored in MSRs are in certain scales. We need to
+	 * convert them into standard units based on the divisors reported in
+	 * the RAPL unit MSRs.
+	 * i.e.
+	 * energy unit: 1/enery_unit_divisor Joules
+	 * power unit: 1/power_unit_divisor Watts
+	 * time unit: 1/time_unit_divisor Seconds
+	 */
+	value = (msr_val & ENERGY_UNIT_MASK) >> ENERGY_UNIT_OFFSET;
+	rp->energy_unit_divisor = 1 << value;
+
+
+	value = (msr_val & POWER_UNIT_MASK) >> POWER_UNIT_OFFSET;
+	rp->power_unit_divisor = 1 << value;
+
+	value = (msr_val & TIME_UNIT_MASK) >> TIME_UNIT_OFFSET;
+	rp->time_unit_divisor = 1 << value;
+
+	pr_debug("Physical package %d units: energy=%d, time=%d, power=%d\n",
+		rp->id,
+		rp->energy_unit_divisor,
+		rp->time_unit_divisor,
+		rp->power_unit_divisor);
+
+	return 0;
+}
+
+/* REVISIT:
+ * When package power limit is set artificially low by RAPL, LVT
+ * thermal interrupt for package power limit should be ignored
+ * since we are not really exceeding the real limit. The intention
+ * is to avoid excessive interrupts while we are trying to save power.
+ * A useful feature might be routing the package_power_limit interrupt
+ * to userspace via eventfd. once we have a usecase, this is simple
+ * to do by adding an atomic notifier.
+ */
+
+static void package_power_limit_irq_save(int package_id)
+{
+	u32 l, h = 0;
+	int cpu;
+	struct rapl_package *rp;
+
+	rp = find_package_by_id(package_id);
+	if (!rp)
+		return;
+
+	if (!boot_cpu_has(X86_FEATURE_PTS) || !boot_cpu_has(X86_FEATURE_PLN))
+		return;
+
+	cpu = find_active_cpu_on_package(package_id);
+	if (cpu < 0)
+		return;
+	/* save the state of PLN irq mask bit before disabling it */
+	rdmsr_safe_on_cpu(cpu, MSR_IA32_PACKAGE_THERM_INTERRUPT, &l, &h);
+	if (!(rp->power_limit_irq & PACKAGE_PLN_INT_SAVED)) {
+		rp->power_limit_irq = l & PACKAGE_THERM_INT_PLN_ENABLE;
+		rp->power_limit_irq |= PACKAGE_PLN_INT_SAVED;
+	}
+	l &= ~PACKAGE_THERM_INT_PLN_ENABLE;
+	wrmsr_on_cpu(cpu, MSR_IA32_PACKAGE_THERM_INTERRUPT, l, h);
+}
+
+/* restore per package power limit interrupt enable state */
+static void package_power_limit_irq_restore(int package_id)
+{
+	u32 l, h;
+	int cpu;
+	struct rapl_package *rp;
+
+	rp = find_package_by_id(package_id);
+	if (!rp)
+		return;
+
+	if (!boot_cpu_has(X86_FEATURE_PTS) || !boot_cpu_has(X86_FEATURE_PLN))
+		return;
+
+	cpu = find_active_cpu_on_package(package_id);
+	if (cpu < 0)
+		return;
+
+	/* irq enable state not saved, nothing to restore */
+	if (!(rp->power_limit_irq & PACKAGE_PLN_INT_SAVED))
+		return;
+	rdmsr_safe_on_cpu(cpu, MSR_IA32_PACKAGE_THERM_INTERRUPT, &l, &h);
+
+	if (rp->power_limit_irq & PACKAGE_THERM_INT_PLN_ENABLE)
+		l |= PACKAGE_THERM_INT_PLN_ENABLE;
+	else
+		l &= ~PACKAGE_THERM_INT_PLN_ENABLE;
+
+	wrmsr_on_cpu(cpu, MSR_IA32_PACKAGE_THERM_INTERRUPT, l, h);
+}
+
+static const struct x86_cpu_id rapl_ids[] = {
+	{ X86_VENDOR_INTEL, 6, 0x2a},/* SNB */
+	{ X86_VENDOR_INTEL, 6, 0x2d},/* SNB EP */
+	{ X86_VENDOR_INTEL, 6, 0x3a},/* IVB */
+	{ X86_VENDOR_INTEL, 6, 0x45},/* HSW */
+	/* TODO: Add more CPU IDs after testing */
+	{}
+};
+MODULE_DEVICE_TABLE(x86cpu, rapl_ids);
+
+/* read once for all raw primitive data for all packages, domains */
+static void rapl_update_domain_data(void)
+{
+	int dmn, prim;
+	u64 val;
+	struct rapl_package *rp;
+
+	list_for_each_entry(rp, &rapl_packages, plist) {
+		for (dmn = 0; dmn < rp->nr_domains; dmn++) {
+			pr_debug("update package %d domain %s data\n", rp->id,
+				rp->domains[dmn].name);
+			/* exclude non-raw primitives */
+			for (prim = 0; prim < NR_RAW_PRIMITIVES; prim++)
+				if (!rapl_read_data_raw(&rp->domains[dmn], prim,
+								rpi[prim].unit,
+								&val))
+					rp->domains[dmn].rdd.primitives[prim] =
+									val;
+		}
+	}
+
+}
+
+static int rapl_unregister_powercap(void)
+{
+	struct rapl_package *rp;
+	struct rapl_domain *rd, *rd_package = NULL;
+
+	/* unregister all active rapl packages from the powercap layer,
+	 * hotplug lock held
+	 */
+	list_for_each_entry(rp, &rapl_packages, plist) {
+		package_power_limit_irq_restore(rp->id);
+
+		for (rd = rp->domains; rd < rp->domains + rp->nr_domains;
+		     rd++) {
+			pr_debug("remove package, undo power limit on %d: %s\n",
+				rp->id, rd->name);
+			rapl_write_data_raw(rd, PL1_ENABLE, 0);
+			rapl_write_data_raw(rd, PL2_ENABLE, 0);
+			rapl_write_data_raw(rd, PL1_CLAMP, 0);
+			rapl_write_data_raw(rd, PL2_CLAMP, 0);
+			if (rd->id == RAPL_DOMAIN_PACKAGE) {
+				rd_package = rd;
+				continue;
+			}
+			powercap_unregister_zone(control_type, &rd->power_zone);
+		}
+		/* do the package zone last */
+		if (rd_package)
+			powercap_unregister_zone(control_type,
+						&rd_package->power_zone);
+	}
+	powercap_unregister_control_type(control_type);
+
+	return 0;
+}
+
+static int rapl_package_register_powercap(struct rapl_package *rp)
+{
+	struct rapl_domain *rd;
+	int ret = 0;
+	char dev_name[17]; /* max domain name = 7 + 1 + 8 for int + 1 for null*/
+	struct powercap_zone *power_zone = NULL;
+	int nr_pl;
+
+	/* first we register package domain as the parent zone*/
+	for (rd = rp->domains; rd < rp->domains + rp->nr_domains; rd++) {
+		if (rd->id == RAPL_DOMAIN_PACKAGE) {
+			nr_pl = find_nr_power_limit(rd);
+			pr_debug("register socket %d package domain %s\n",
+				rp->id, rd->name);
+			memset(dev_name, 0, sizeof(dev_name));
+			snprintf(dev_name, sizeof(dev_name), "%s-%d",
+				rd->name, rp->id);
+			power_zone = powercap_register_zone(&rd->power_zone,
+							control_type,
+							dev_name, NULL,
+							&zone_ops[rd->id],
+							nr_pl,
+							&constraint_ops);
+			if (IS_ERR(power_zone)) {
+				pr_debug("failed to register package, %d\n",
+					rp->id);
+				ret = PTR_ERR(power_zone);
+				goto exit_package;
+			}
+			/* track parent zone in per package/socket data */
+			rp->power_zone = power_zone;
+			/* done, only one package domain per socket */
+			break;
+		}
+	}
+	if (!power_zone) {
+		pr_err("no package domain found, unknown topology!\n");
+		ret = -ENODEV;
+		goto exit_package;
+	}
+	/* now register domains as children of the socket/package*/
+	for (rd = rp->domains; rd < rp->domains + rp->nr_domains; rd++) {
+		if (rd->id == RAPL_DOMAIN_PACKAGE)
+			continue;
+		/* number of power limits per domain varies */
+		nr_pl = find_nr_power_limit(rd);
+		power_zone = powercap_register_zone(&rd->power_zone,
+						control_type, rd->name,
+						rp->power_zone,
+						&zone_ops[rd->id], nr_pl,
+						&constraint_ops);
+
+		if (IS_ERR(power_zone)) {
+			pr_debug("failed to register power_zone, %d:%s:%s\n",
+				rp->id, rd->name, dev_name);
+			ret = PTR_ERR(power_zone);
+			goto err_cleanup;
+		}
+	}
+
+exit_package:
+	return ret;
+err_cleanup:
+	/* clean up previously initialized domains within the package if we
+	 * failed after the first domain setup.
+	 */
+	while (--rd >= rp->domains) {
+		pr_debug("unregister package %d domain %s\n", rp->id, rd->name);
+		powercap_unregister_zone(control_type, &rd->power_zone);
+	}
+
+	return ret;
+}
+
+static int rapl_register_powercap(void)
+{
+	struct rapl_domain *rd;
+	struct rapl_package *rp;
+	int ret = 0;
+
+	control_type = powercap_register_control_type(NULL, "intel-rapl", NULL);
+	if (IS_ERR(control_type)) {
+		pr_debug("failed to register powercap control_type.\n");
+		return PTR_ERR(control_type);
+	}
+	/* read the initial data */
+	rapl_update_domain_data();
+	list_for_each_entry(rp, &rapl_packages, plist)
+		if (rapl_package_register_powercap(rp))
+			goto err_cleanup_package;
+	return ret;
+
+err_cleanup_package:
+	/* clean up previously initialized packages */
+	list_for_each_entry_continue_reverse(rp, &rapl_packages, plist) {
+		for (rd = rp->domains; rd < rp->domains + rp->nr_domains;
+		     rd++) {
+			pr_debug("unregister zone/package %d, %s domain\n",
+				rp->id, rd->name);
+			powercap_unregister_zone(control_type, &rd->power_zone);
+		}
+	}
+
+	return ret;
+}
+
+static int rapl_check_domain(int cpu, int domain)
+{
+	unsigned msr;
+	u64 val1, val2 = 0;
+	int retry = 0;
+
+	switch (domain) {
+	case RAPL_DOMAIN_PACKAGE:
+		msr = MSR_PKG_ENERGY_STATUS;
+		break;
+	case RAPL_DOMAIN_PP0:
+		msr = MSR_PP0_ENERGY_STATUS;
+		break;
+	case RAPL_DOMAIN_PP1:
+		msr = MSR_PP1_ENERGY_STATUS;
+		break;
+	case RAPL_DOMAIN_DRAM:
+		msr = MSR_DRAM_ENERGY_STATUS;
+		break;
+	default:
+		pr_err("invalid domain id %d\n", domain);
+		return -EINVAL;
+	}
+	if (rdmsrl_safe_on_cpu(cpu, msr, &val1))
+		return -ENODEV;
+
+	/* energy counters roll slowly on some domains */
+	while (++retry < 10) {
+		usleep_range(10000, 15000);
+		rdmsrl_safe_on_cpu(cpu, msr, &val2);
+		if ((val1 & ENERGY_STATUS_MASK) != (val2 & ENERGY_STATUS_MASK))
+			return 0;
+	}
+	/* if energy counter does not change, report as bad domain */
+	pr_info("domain %s energy ctr %llu:%llu not working, skip\n",
+		rapl_domain_names[domain], val1, val2);
+
+	return -ENODEV;
+}
+
+/* Detect active and valid domains for the given CPU, caller must
+ * ensure the CPU belongs to the targeted package and CPU hotlug is disabled.
+ */
+static int rapl_detect_domains(struct rapl_package *rp, int cpu)
+{
+	int i;
+	int ret = 0;
+	struct rapl_domain *rd;
+	u64 locked;
+
+	for (i = 0; i < RAPL_DOMAIN_MAX; i++) {
+		/* use physical package id to read counters */
+		if (!rapl_check_domain(cpu, i))
+			rp->domain_map |= 1 << i;
+	}
+	rp->nr_domains = bitmap_weight(&rp->domain_map,	RAPL_DOMAIN_MAX);
+	if (!rp->nr_domains) {
+		pr_err("no valid rapl domains found in package %d\n", rp->id);
+		ret = -ENODEV;
+		goto done;
+	}
+	pr_debug("found %d domains on package %d\n", rp->nr_domains, rp->id);
+
+	rp->domains = kcalloc(rp->nr_domains + 1, sizeof(struct rapl_domain),
+			GFP_KERNEL);
+	if (!rp->domains) {
+		ret = -ENOMEM;
+		goto done;
+	}
+	rapl_init_domains(rp);
+
+	for (rd = rp->domains; rd < rp->domains + rp->nr_domains; rd++) {
+		/* check if the domain is locked by BIOS */
+		if (rapl_read_data_raw(rd, FW_LOCK, false, &locked)) {
+			pr_info("RAPL package %d domain %s locked by BIOS\n",
+				rp->id, rd->name);
+				rd->state |= DOMAIN_STATE_BIOS_LOCKED;
+		}
+	}
+
+
+done:
+	return ret;
+}
+
+static bool is_package_new(int package)
+{
+	struct rapl_package *rp;
+
+	/* caller prevents cpu hotplug, there will be no new packages added
+	 * or deleted while traversing the package list, no need for locking.
+	 */
+	list_for_each_entry(rp, &rapl_packages, plist)
+		if (package == rp->id)
+			return false;
+
+	return true;
+}
+
+/* RAPL interface can be made of a two-level hierarchy: package level and domain
+ * level. We first detect the number of packages then domains of each package.
+ * We have to consider the possiblity of CPU online/offline due to hotplug and
+ * other scenarios.
+ */
+static int rapl_detect_topology(void)
+{
+	int i;
+	int phy_package_id;
+	struct rapl_package *new_package, *rp;
+
+	for_each_online_cpu(i) {
+		phy_package_id = topology_physical_package_id(i);
+		if (is_package_new(phy_package_id)) {
+			new_package = kzalloc(sizeof(*rp), GFP_KERNEL);
+			if (!new_package) {
+				rapl_cleanup_data();
+				return -ENOMEM;
+			}
+			/* add the new package to the list */
+			new_package->id = phy_package_id;
+			new_package->nr_cpus = 1;
+
+			/* check if the package contains valid domains */
+			if (rapl_detect_domains(new_package, i) ||
+				rapl_check_unit(new_package, i)) {
+				kfree(new_package->domains);
+				kfree(new_package);
+				/* free up the packages already initialized */
+				rapl_cleanup_data();
+				return -ENODEV;
+			}
+			INIT_LIST_HEAD(&new_package->plist);
+			list_add(&new_package->plist, &rapl_packages);
+		} else {
+			rp = find_package_by_id(phy_package_id);
+			if (rp)
+				++rp->nr_cpus;
+		}
+	}
+
+	return 0;
+}
+
+/* called from CPU hotplug notifier, hotplug lock held */
+static void rapl_remove_package(struct rapl_package *rp)
+{
+	struct rapl_domain *rd, *rd_package = NULL;
+
+	for (rd = rp->domains; rd < rp->domains + rp->nr_domains; rd++) {
+		if (rd->id == RAPL_DOMAIN_PACKAGE) {
+			rd_package = rd;
+			continue;
+		}
+		pr_debug("remove package %d, %s domain\n", rp->id, rd->name);
+		powercap_unregister_zone(control_type, &rd->power_zone);
+	}
+	/* do parent zone last */
+	powercap_unregister_zone(control_type, &rd_package->power_zone);
+	list_del(&rp->plist);
+	kfree(rp);
+}
+
+/* called from CPU hotplug notifier, hotplug lock held */
+static int rapl_add_package(int cpu)
+{
+	int ret = 0;
+	int phy_package_id;
+	struct rapl_package *rp;
+
+	phy_package_id = topology_physical_package_id(cpu);
+	rp = kzalloc(sizeof(struct rapl_package), GFP_KERNEL);
+	if (!rp)
+		return -ENOMEM;
+
+	/* add the new package to the list */
+	rp->id = phy_package_id;
+	rp->nr_cpus = 1;
+	/* check if the package contains valid domains */
+	if (rapl_detect_domains(rp, cpu) ||
+		rapl_check_unit(rp, cpu)) {
+		ret = -ENODEV;
+		goto err_free_package;
+	}
+	if (!rapl_package_register_powercap(rp)) {
+		INIT_LIST_HEAD(&rp->plist);
+		list_add(&rp->plist, &rapl_packages);
+		return ret;
+	}
+
+err_free_package:
+	kfree(rp->domains);
+	kfree(rp);
+
+	return ret;
+}
+
+/* Handles CPU hotplug on multi-socket systems.
+ * If a CPU goes online as the first CPU of the physical package
+ * we add the RAPL package to the system. Similarly, when the last
+ * CPU of the package is removed, we remove the RAPL package and its
+ * associated domains. Cooling devices are handled accordingly at
+ * per-domain level.
+ */
+static int rapl_cpu_callback(struct notifier_block *nfb,
+				unsigned long action, void *hcpu)
+{
+	unsigned long cpu = (unsigned long)hcpu;
+	int phy_package_id;
+	struct rapl_package *rp;
+
+	phy_package_id = topology_physical_package_id(cpu);
+	switch (action) {
+	case CPU_ONLINE:
+	case CPU_ONLINE_FROZEN:
+	case CPU_DOWN_FAILED:
+	case CPU_DOWN_FAILED_FROZEN:
+		rp = find_package_by_id(phy_package_id);
+		if (rp)
+			++rp->nr_cpus;
+		else
+			rapl_add_package(cpu);
+		break;
+	case CPU_DOWN_PREPARE:
+	case CPU_DOWN_PREPARE_FROZEN:
+		rp = find_package_by_id(phy_package_id);
+		if (!rp)
+			break;
+		if (--rp->nr_cpus == 0)
+			rapl_remove_package(rp);
+	}
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block rapl_cpu_notifier = {
+	.notifier_call = rapl_cpu_callback,
+};
+
+static int __init rapl_init(void)
+{
+	int ret = 0;
+
+	if (!x86_match_cpu(rapl_ids)) {
+		pr_err("driver does not support CPU family %d model %d\n",
+			boot_cpu_data.x86, boot_cpu_data.x86_model);
+
+		return -ENODEV;
+	}
+	/* prevent CPU hotplug during detection */
+	get_online_cpus();
+	ret = rapl_detect_topology();
+	if (ret)
+		goto done;
+
+	if (rapl_register_powercap()) {
+		rapl_cleanup_data();
+		ret = -ENODEV;
+		goto done;
+	}
+	register_hotcpu_notifier(&rapl_cpu_notifier);
+done:
+	put_online_cpus();
+
+	return ret;
+}
+
+static void __exit rapl_exit(void)
+{
+	get_online_cpus();
+	unregister_hotcpu_notifier(&rapl_cpu_notifier);
+	rapl_unregister_powercap();
+	rapl_cleanup_data();
+	put_online_cpus();
+}
+
+module_init(rapl_init);
+module_exit(rapl_exit);
+
+MODULE_DESCRIPTION("Driver for Intel RAPL (Running Average Power Limit)");
+MODULE_AUTHOR("Jacob Pan <jacob.jun.pan@intel.com>");
+MODULE_LICENSE("GPL v2");