new file mode 100644
@@ -0,0 +1,307 @@
+ =======================
+ INTEL POWERCLAMP DRIVER
+ =======================
+By: Arjan van de Ven <arjan@linux.intel.com>
+ Jacob Pan <jacob.jun.pan@linux.intel.com>
+
+Contents:
+ (*) Introduction
+ - Goals and Objectives
+
+ (*) Theory of Operation
+ - Idle Injection
+ - Calibration
+
+ (*) Performance Analysis
+ - Effectiveness and Limitations
+ - Power vs Performance
+ - Scalability
+ - Calibration
+ - Comparison with Alternative Techniques
+
+ (*) Usage and Interfaces
+ - Generic Thermal Layer (sysfs)
+ - Kernel APIs (TBD)
+
+============
+INTRODUCTION
+============
+
+Consider the situation where a system’s power consumption must be
+reduced at runtime, due to power budget, thermal constraint, or noise
+level, and where active cooling is not preferred. Software managed
+passive power reduction must be performed to prevent the hardware
+actions that are designed for catastrophic scenarios.
+
+Currently, P-states, T-states (clock modulation), and CPU offlining
+are used for CPU throttling.
+
+On Intel CPUs, C-states provide effective power reduction, but so far
+they’re only used opportunistically, based on workload. With the
+development of intel_powerclamp driver, the method of synchronizing
+idle injection across all online CPU threads was introduced. The goal
+is to achieve forced and controllable C-state residency.
+
+Test/Analysis has been made in the areas of power, performance,
+scalability, and user experience. In many cases, clear advantage is
+shown over taking the CPU offline or modulating the CPU clock.
+
+
+===================
+THEORY OF OPERATION
+===================
+
+Idle Injection
+--------------
+
+On modern Intel processors (Nehalem or later), package level C-state
+residency is available in MSRs, thus also available to the kernel.
+
+These MSRs are:
+ #define MSR_PKG_C2_RESIDENCY 0x60D
+ #define MSR_PKG_C3_RESIDENCY 0x3F8
+ #define MSR_PKG_C6_RESIDENCY 0x3F9
+ #define MSR_PKG_C7_RESIDENCY 0x3FA
+
+If the kernel can also inject idle time to the system, then a
+closed-loop control system can be established that manages package
+level C-state. The intel_powerclamp driver is conceived as such a
+control system, where the target set point is a user-selected idle
+ratio (based on power reduction), and the error is the difference
+between the actual package level C-state residency ratio and the target idle
+ratio.
+
+Injection is controlled by high priority kernel threads, spawned for
+each online CPU.
+
+These kernel threads, with SCHED_FIFO class, are created to perform
+clamping actions of controlled duty ratio and duration. Each per-CPU
+thread synchronizes its idle time and duration, based on the rounding
+of jiffies, so accumulated errors can be prevented to avoid a jittery
+effect. Threads are also bound to the CPU such that they cannot be
+migrated, unless the CPU is taken offline. In this case, threads
+belong to the offlined CPUs will be terminated immediately.
+
+Running as SCHED_FIFO and relatively high priority, also allows such
+scheme to work for both preemptable and non-preemptable kernels.
+Alignment of idle time around jiffies ensures scalability for HZ
+values. This effect can be better visualized using a Perf timechart.
+The following diagram shows the behavior of kernel thread
+kidle_inject/cpu. During idle injection, it runs monitor/mwait idle
+for a given "duration", then relinquishes the CPU to other tasks,
+until the next time interval.
+
+The NOHZ schedule tick is disabled during idle time, but interrupts
+are not masked. Tests show that the extra wakeups from scheduler tick
+have a dramatic impact on the effectiveness of the powerclamp driver
+on large scale systems (Westmere system with 80 processors).
+
+CPU0
+ ____________ ____________
+kidle_inject/0 | sleep | mwait | sleep |
+ _________| |________| |_______
+ duration
+CPU1
+ ____________ ____________
+kidle_inject/1 | sleep | mwait | sleep |
+ _________| |________| |_______
+ ^
+ |
+ |
+ roundup(jiffies, interval)
+
+Only one CPU is allowed to collect statistics and update global
+control parameters. This CPU is referred to as the controlling CPU in
+this document. The controlling CPU is elected at runtime, with a
+policy that favors BSP, taking into account the possibility of a CPU
+hot-plug.
+
+In terms of dynamics of the idle control system, package level idle
+time is considered largely as a non-causal system where its behavior
+cannot be based on the past or current input. Therefore, the
+intel_powerclamp driver attempts to enforce the desired idle time
+instantly as given input (target idle ratio). After injection,
+powerclamp moniors the actual idle for a given time window and adjust
+the next injection accordingly to avoid over/under correction.
+
+When used in a causal control system, such as a temperature control,
+it is up to the user of this driver to implement algorithms where
+past samples and outputs are included in the feedback. For example, a
+PID-based thermal controller can use the powerclamp driver to
+maintain a desired target temperature, based on integral and
+derivative gains of the past samples.
+
+
+
+Calibration
+-----------
+During scalability testing, it is observed that synchronized actions
+among CPUs become challenging as the number of cores grows. This is
+also true for the ability of a system to enter package level C-states.
+
+To make sure the intel_powerclamp driver scales well, online
+calibration is implemented. The goals for doing such a calibration
+are:
+
+a) determine the effective range of idle injection ratio
+b) determine the amount of compensation needed at each target ratio
+
+Compensation to each target ratio consists of two parts:
+
+ a) steady state error compensation
+ This is to offset the error occurring when the system can
+ enter idle without extra wakeups (such as external interrupts).
+
+ b) dynamic error compensation
+ When an excessive amount of wakeups occurs during idle, an
+ additional idle ratio can be added to quiet interrupts, by
+ slowing down CPU activities.
+
+A debugfs file is provided for the user to examine compensation
+progress and results, such as on a Westmere system.
+[jacob@nex01 ~]$ cat
+/sys/kernel/debug/intel_powerclamp/powerclamp_calib
+controlling cpu: 0
+pct confidence steady dynamic (compensation)
+0 0 0 0
+1 1 0 0
+2 1 1 0
+3 3 1 0
+4 3 1 0
+5 3 1 0
+6 3 1 0
+7 3 1 0
+8 3 1 0
+...
+30 3 2 0
+31 3 2 0
+32 3 1 0
+33 3 2 0
+34 3 1 0
+35 3 2 0
+36 3 1 0
+37 3 2 0
+38 3 1 0
+39 3 2 0
+40 3 3 0
+41 3 1 0
+42 3 2 0
+43 3 1 0
+44 3 1 0
+45 3 2 0
+46 3 3 0
+47 3 0 0
+48 3 2 0
+49 3 3 0
+
+Calibration occurs during runtime. No offline method is available.
+Steady state compensation is used only when confidence levels of all
+adjacent ratios have reached satisfactory level. A confidence level
+is accumulated based on clean data collected at runtime. Data
+collected during a period without extra interrupts is considered
+clean.
+
+To compensate for excessive amounts of wakeup during idle, additional
+idle time is injected when such a condition is detected. Currently,
+we have a simple algorithm to double the injection ratio. A possible
+enhancement might be to throttle the offending IRQ, such as delaying
+EOI for level triggered interrupts. But it is a challenge to be
+non-intrusive to the scheduler or the IRQ core code.
+
+
+CPU Online/Offline
+------------------
+Per-CPU kernel threads are started/stopped upon receiving
+notifications of CPU hotplug activities. The intel_powerclamp driver
+keeps track of clamping kernel threads, even after they are migrated
+to other CPUs, after a CPU offline event.
+
+
+=====================
+Performance Analysis
+=====================
+This section describes the general performance data collected on
+multiple systems, including Westmere (80P) and Ivy Bridge (4P, 8P).
+
+Effectiveness and Limitations
+-----------------------------
+The maximum range that idle injection is allowed is capped at 50
+percent. As mentioned earlier, since interrupts are allowed during
+forced idle time, excessive interrupts could result in less
+effectiveness. The extreme case would be doing a ping -f to generated
+flooded network interrupts without much CPU acknowledgement. In this
+case, little can be done from the idle injection threads. In most
+normal cases, such as scp a large file, applications can be throttled
+by the powerclamp driver, since slowing down the CPU also slows down
+network protocol processing, which in turn reduces interrupts.
+
+When control parameters change at runtime by the controlling CPU, it
+may take an additional period for the rest of the CPUs to catch up
+with the changes. During this time, idle injection is out of sync,
+thus not able to enter package C- states at the expected ratio. But
+this effect is minor, in that in most cases change to the target
+ratio is updated much less frequently than the idle injection
+frequency.
+
+Scalability
+-----------
+Tests also show a minor, but measurable, difference between the 4P/8P
+Ivy Bridge system and the 80P Westmere server under 50% idle ratio.
+More compensation is needed on Westmere for the same amount of
+target idle ratio. The compensation also increases as the idle ratio
+gets larger. The above reason constitutes the need for the
+calibration code.
+
+On the IVB 8P system, compared to an offline CPU, powerclamp can
+achieve up to 40% better performance per watt. (measured by a spin
+counter summed over per CPU counting threads spawned for all running
+CPUs).
+
+====================
+Usage and Interfaces
+====================
+The powerclamp driver is registered to the generic thermal layer as a
+cooling device. Currently, it’s not bound to any thermal zones.
+
+jacob@chromoly:/sys/class/thermal/cooling_device14$ grep . *
+cur_state:0
+max_state:50
+type:intel_powerclamp
+
+Example usage:
+- To inject 25% idle time
+$ sudo sh -c "echo 25 > /sys/class/thermal/cooling_device80/cur_state
+"
+
+If the system is not busy and has more than 25% idle time already,
+then the powerclamp driver will not start idle injection. Using Top
+will not show idle injection kernel threads.
+
+If the system is busy (spin test below) and has less than 25% natural
+idle time, powerclamp kernel threads will do idle injection, which
+appear running to the scheduler. But the overall system idle is still
+reflected. In this example, 24.1% idle is shown. This helps the
+system admin or user determine the cause of slowdown, when a
+powerclamp driver is in action.
+
+
+Tasks: 197 total, 1 running, 196 sleeping, 0 stopped, 0 zombie
+Cpu(s): 71.2%us, 4.7%sy, 0.0%ni, 24.1%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
+Mem: 3943228k total, 1689632k used, 2253596k free, 74960k buffers
+Swap: 4087804k total, 0k used, 4087804k free, 945336k cached
+
+ PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
+ 3352 jacob 20 0 262m 644 428 S 286 0.0 0:17.16 spin
+ 3341 root -51 0 0 0 0 D 25 0.0 0:01.62 kidle_inject/0
+ 3344 root -51 0 0 0 0 D 25 0.0 0:01.60 kidle_inject/3
+ 3342 root -51 0 0 0 0 D 25 0.0 0:01.61 kidle_inject/1
+ 3343 root -51 0 0 0 0 D 25 0.0 0:01.60 kidle_inject/2
+ 2935 jacob 20 0 696m 125m 35m S 5 3.3 0:31.11 firefox
+ 1546 root 20 0 158m 20m 6640 S 3 0.5 0:26.97 Xorg
+ 2100 jacob 20 0 1223m 88m 30m S 3 2.3 0:23.68 compiz
+
+Tests have shown that by using the powerclamp driver as a cooling
+device, a PID based userspace thermal controller can manage to
+control CPU temperature effectively, when no other thermal influence
+is added. For example, a UltraBook user can compile the kernel under
+certain temperature (below most active trip points).
@@ -122,4 +122,14 @@ config DB8500_CPUFREQ_COOLING
bound cpufreq cooling device turns active to set CPU frequency low to
cool down the CPU.
+config INTEL_POWERCLAMP
+ tristate "Intel PowerClamp idle injection driver"
+ depends on THERMAL
+ depends on X86
+ depends on CPU_SUP_INTEL
+ help
+ Enable this to enable Intel PowerClamp idle injection driver. This
+ enforce idle time which results in more package C-state residency. The
+ user interface is exposed via generic thermal framework.
+
endif
@@ -18,3 +18,5 @@ obj-$(CONFIG_RCAR_THERMAL) += rcar_thermal.o
obj-$(CONFIG_EXYNOS_THERMAL) += exynos_thermal.o
obj-$(CONFIG_DB8500_THERMAL) += db8500_thermal.o
obj-$(CONFIG_DB8500_CPUFREQ_COOLING) += db8500_cpufreq_cooling.o
+obj-$(CONFIG_INTEL_POWERCLAMP) += intel_powerclamp.o
+
new file mode 100644
@@ -0,0 +1,762 @@
+/*
+ * intel_powerclamp.c - package c-state idle injection
+ *
+ * Copyright (c) 2012, Intel Corporation.
+ *
+ * Authors:
+ * Arjan van de Ven <arjan@linux.intel.com>
+ * Jacob Pan <jacob.jun.pan@linux.intel.com>
+ *
+ * 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.,
+ * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ *
+ * TODO:
+ * 1. better handle wakeup from external interrupts, currently a fixed
+ * compensation is added to clamping duration when excessive amount
+ * of wakeups are observed during idle time. the reason is that in
+ * case of external interrupts without need for ack, clamping down
+ * cpu in non-irq context does not reduce irq. for majority of the
+ * cases, clamping down cpu does help reduce irq as well, we should
+ * be able to differenciate the two cases and give a quantitative
+ * solution for the irqs that we can control. perhaps based on
+ * get_cpu_iowait_time_us()
+ *
+ * 2. synchronization with other hw blocks
+ *
+ *
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/delay.h>
+#include <linux/kthread.h>
+#include <linux/freezer.h>
+#include <linux/cpu.h>
+#include <linux/thermal.h>
+#include <linux/slab.h>
+#include <linux/tick.h>
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
+#include <linux/nmi.h>
+
+#include <asm/msr.h>
+#include <asm/mwait.h>
+#include <asm/cpu_device_id.h>
+#include <asm/idle.h>
+#include <asm/hardirq.h>
+
+#define MSR_PKG_C2_RESIDENCY 0x60D
+#define MSR_PKG_C3_RESIDENCY 0x3F8
+#define MSR_PKG_C6_RESIDENCY 0x3F9
+#define MSR_PKG_C7_RESIDENCY 0x3FA
+
+#define MAX_TARGET_RATIO (50U)
+/* For each undisturbed clamping period (no extra wake ups during idle time),
+ * we increment the confidence counter for the given target ratio.
+ * CONFIDENCE_OK defines the level where runtime calibration results are
+ * valid.
+ */
+#define CONFIDENCE_OK (3)
+/* Default idle injection duration, driver adjust sleep time to meet target
+ * idle ratio. Similar to frequency modulation.
+ */
+#define DEFAULT_DURATION_JIFFIES (6)
+
+static unsigned int target_mwait;
+static struct dentry *debug_dir;
+
+/* user selected target */
+static unsigned int set_target_ratio;
+static unsigned int current_ratio;
+static bool should_skip;
+static bool reduce_irq;
+static atomic_t idle_wakeup_counter;
+static unsigned int control_cpu; /* The cpu assigned to collect stat and update
+ * control parameters. default to BSP but BSP
+ * can be offlined.
+ */
+static int clamping;
+
+
+static struct task_struct __percpu **powerclamp_thread;
+static struct thermal_cooling_device *cooling_dev;
+static unsigned long *cpu_clamping_mask; /* bit map for tracking per cpu
+ * clamping thread
+ */
+static int duration;
+module_param(duration, int, 0600);
+MODULE_PARM_DESC(duration, "forced idle time for each attempt in msec.");
+
+static unsigned int pkg_cstate_ratio_cur;
+static unsigned int window_size;
+
+struct powerclamp_calibration_data {
+ unsigned long confidence; /* used for calibration, basically a counter
+ * gets incremented each time a clamping
+ * period is completed without extra wakeups
+ * once that counter is reached given level,
+ * compensation is deemed usable.
+ */
+ unsigned long steady_comp; /* steady state compensation used when
+ * no extra wakeups occurred.
+ */
+ unsigned long dynamic_comp; /* compensate excessive wakeup from idle
+ * mostly from external interrupts.
+ */
+};
+
+static struct powerclamp_calibration_data cal_data[MAX_TARGET_RATIO];
+
+static int window_size_set(const char *arg, const struct kernel_param *kp)
+{
+ int ret = 0;
+ unsigned long new_window_size;
+
+ ret = kstrtoul(arg, 10, &new_window_size);
+ if (ret)
+ goto exit_win;
+ if (new_window_size >= 10 || new_window_size < 2) {
+ pr_err("Invalid window size %lu, between 2-10\n",
+ new_window_size);
+ ret = -EINVAL;
+ }
+
+ window_size = new_window_size;
+ smp_mb();
+
+exit_win:
+
+ return ret;
+}
+static struct kernel_param_ops window_size_ops = {
+ .set = window_size_set,
+ .get = param_get_int,
+};
+
+module_param_cb(window_size, &window_size_ops, &window_size, 0644);
+MODULE_PARM_DESC(window_size, "sliding window in number of clamping cycles\n"
+ "\tpowerclamp controls idle ratio within this window. larger\n"
+ "\twindow size results in slower response time but more smooth\n"
+ "\tclamping results. default to 2.");
+
+static void find_target_mwait(void)
+{
+ unsigned int eax, ebx, ecx, edx;
+ unsigned int highest_cstate = 0;
+ unsigned int highest_subcstate = 0;
+ int i;
+
+ if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
+ return;
+
+ cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx);
+
+ if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) ||
+ !(ecx & CPUID5_ECX_INTERRUPT_BREAK))
+ return;
+
+ edx >>= MWAIT_SUBSTATE_SIZE;
+ for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) {
+ if (edx & MWAIT_SUBSTATE_MASK) {
+ highest_cstate = i;
+ highest_subcstate = edx & MWAIT_SUBSTATE_MASK;
+ }
+ }
+ target_mwait = (highest_cstate << MWAIT_SUBSTATE_SIZE) |
+ (highest_subcstate - 1);
+
+}
+
+static u64 pkg_state_counter(void)
+{
+ u64 val;
+ u64 count = 0;
+
+ static bool skip_c2;
+ static bool skip_c3;
+ static bool skip_c6;
+ static bool skip_c7;
+
+ if (!skip_c2) {
+ if (!rdmsrl_safe(MSR_PKG_C2_RESIDENCY, &val))
+ count += val;
+ else
+ skip_c2 = true;
+ }
+
+ if (!skip_c3) {
+ if (!rdmsrl_safe(MSR_PKG_C3_RESIDENCY, &val))
+ count += val;
+ else
+ skip_c3 = true;
+ }
+
+ if (!skip_c6) {
+ if (!rdmsrl_safe(MSR_PKG_C6_RESIDENCY, &val))
+ count += val;
+ else
+ skip_c6 = true;
+ }
+
+ if (!skip_c7) {
+ if (!rdmsrl_safe(MSR_PKG_C7_RESIDENCY, &val))
+ count += val;
+ else
+ skip_c7 = true;
+ }
+
+ return count;
+}
+
+static void noop_timer(unsigned long foo)
+{
+ /* empty... just the fact that we get the interrupt wakes us up */
+}
+
+static unsigned int get_compensation(int ratio)
+{
+ unsigned int comp = 0;
+
+ /* we only use compensation if all adjacent ones are good */
+ if (ratio == 1 &&
+ cal_data[ratio].confidence >= CONFIDENCE_OK &&
+ cal_data[ratio + 1].confidence >= CONFIDENCE_OK &&
+ cal_data[ratio + 2].confidence >= CONFIDENCE_OK) {
+ comp = (cal_data[ratio].steady_comp +
+ cal_data[ratio + 1].steady_comp +
+ cal_data[ratio + 2].steady_comp) / 3;
+ } else if (ratio == MAX_TARGET_RATIO - 1 &&
+ cal_data[ratio].confidence >= CONFIDENCE_OK &&
+ cal_data[ratio - 1].confidence >= CONFIDENCE_OK &&
+ cal_data[ratio - 2].confidence >= CONFIDENCE_OK) {
+ comp = (cal_data[ratio].steady_comp +
+ cal_data[ratio - 1].steady_comp +
+ cal_data[ratio - 2].steady_comp) / 3;
+ } else if (cal_data[ratio].confidence >= CONFIDENCE_OK &&
+ cal_data[ratio - 1].confidence >= CONFIDENCE_OK &&
+ cal_data[ratio + 1].confidence >= CONFIDENCE_OK) {
+ comp = (cal_data[ratio].steady_comp +
+ cal_data[ratio - 1].steady_comp +
+ cal_data[ratio + 1].steady_comp) / 3;
+ }
+
+ /* REVISIT: simple penalty of double idle injection */
+ if (reduce_irq)
+ comp = ratio;
+ /* do not exceed limit */
+ if (comp + ratio >= MAX_TARGET_RATIO)
+ comp = MAX_TARGET_RATIO - ratio - 1;
+
+ return comp;
+}
+
+static void adjust_compensation(int target_ratio, unsigned int win)
+{
+ int delta;
+ struct powerclamp_calibration_data *d = &cal_data[target_ratio];
+
+ /*
+ * adjust compensations if confidence level has not been reached or
+ * there are too many wakeups during the last idle injection period, we
+ * cannot trust the data for compensation.
+ */
+ if (d->confidence >= CONFIDENCE_OK ||
+ atomic_read(&idle_wakeup_counter) >
+ win * num_online_cpus())
+ return;
+
+ delta = set_target_ratio - current_ratio;
+ /* filter out bad data */
+ if (delta >= 0 && delta <= (1+target_ratio/10)) {
+ if (d->steady_comp)
+ d->steady_comp =
+ roundup(delta+d->steady_comp, 2)/2;
+ else
+ d->steady_comp = delta;
+ d->confidence++;
+ }
+}
+
+static bool powerclamp_adjust_controls(unsigned int target_ratio,
+ unsigned int guard, unsigned int win)
+{
+ static u64 msr_last, tsc_last;
+ u64 msr_now, tsc_now;
+
+ /* check result for the last window */
+ msr_now = pkg_state_counter();
+ rdtscll(tsc_now);
+
+ /* calculate pkg cstate vs tsc ratio */
+ if (!msr_last || !tsc_last)
+ current_ratio = 1;
+ else if (tsc_now-tsc_last)
+ current_ratio = 100*(msr_now-msr_last)/
+ (tsc_now-tsc_last);
+
+ /* update record */
+ msr_last = msr_now;
+ tsc_last = tsc_now;
+
+ adjust_compensation(target_ratio, win);
+ /*
+ * too many external interrupts, set flag such
+ * that we can take measure later.
+ */
+ reduce_irq = atomic_read(&idle_wakeup_counter) >=
+ 2 * win * num_online_cpus();
+
+ atomic_set(&idle_wakeup_counter, 0);
+ /* if we are above target+guard, skip */
+ return set_target_ratio + guard <= current_ratio;
+}
+
+static int clamp_thread(void *arg)
+{
+ int cpunr = (unsigned long)arg;
+ DEFINE_TIMER(wakeup_timer, noop_timer, 0, 0);
+ static const struct sched_param param = {
+ .sched_priority = MAX_USER_RT_PRIO/2,
+ };
+ unsigned int count = 0;
+ unsigned int target_ratio;
+
+ set_bit(cpunr, cpu_clamping_mask);
+ set_freezable();
+ init_timer_on_stack(&wakeup_timer);
+ sched_setscheduler(current, SCHED_FIFO, ¶m);
+
+ while (clamping && !kthread_should_stop() && cpu_online(cpunr)) {
+ int sleeptime;
+ unsigned long target_jiffies;
+ unsigned int guard;
+ unsigned int compensation = 0;
+ int interval; /* jiffies to sleep for each attempt */
+ unsigned int duration_jiffies = msecs_to_jiffies(duration);
+ unsigned int window_size_now;
+
+ try_to_freeze();
+ /*
+ * make sure user selected ratio does not take effect until
+ * the next round. adjust target_ratio if user has changed
+ * target such that we can converge quickly.
+ */
+ target_ratio = set_target_ratio;
+ guard = 1 + target_ratio/20;
+ window_size_now = window_size;
+ count++;
+
+ /*
+ * systems may have different ability to enter package level
+ * c-states, thus we need to compensate the injected idle ratio
+ * to achieve the actual target reported by the HW.
+ */
+ compensation = get_compensation(target_ratio);
+ interval = duration_jiffies*100/(target_ratio+compensation);
+
+ /* align idle time */
+ target_jiffies = roundup(jiffies, interval);
+ sleeptime = target_jiffies - jiffies;
+ if (sleeptime <= 0)
+ sleeptime = 1;
+ schedule_timeout_interruptible(sleeptime);
+ /*
+ * only elected controlling cpu can collect stats and update
+ * control parameters.
+ */
+ if (cpunr == control_cpu && !(count%window_size_now)) {
+ should_skip =
+ powerclamp_adjust_controls(target_ratio,
+ guard, window_size_now);
+ smp_mb();
+ }
+
+ if (should_skip)
+ continue;
+
+ target_jiffies = jiffies + duration_jiffies;
+ mod_timer(&wakeup_timer, target_jiffies);
+ if (unlikely(local_softirq_pending()))
+ continue;
+ /*
+ * stop tick sched during idle time, interrupts are still
+ * allowed. thus jiffies are updated properly.
+ */
+ preempt_disable();
+ tick_nohz_idle_enter();
+ /* mwait until target jiffies is reached */
+ while (time_before(jiffies, target_jiffies)) {
+ unsigned long ecx = 1;
+ unsigned long eax = target_mwait;
+
+ /*
+ * REVISIT: may call enter_idle() to notify drivers who
+ * can save power during cpu idle. same for exit_idle()
+ */
+ local_touch_nmi();
+ stop_critical_timings();
+ __monitor((void *)¤t_thread_info()->flags, 0, 0);
+ cpu_relax(); /* allow HT sibling to run */
+ __mwait(eax, ecx);
+ start_critical_timings();
+ atomic_inc(&idle_wakeup_counter);
+ }
+ tick_nohz_idle_exit();
+ preempt_enable_no_resched();
+ }
+ del_timer_sync(&wakeup_timer);
+ clear_bit(cpunr, cpu_clamping_mask);
+
+ return 0;
+}
+
+/*
+ * 1 HZ polling while clamping is active, useful for userspace
+ * to monitor actual idle ratio.
+ */
+static void poll_pkg_cstate(struct work_struct *dummy);
+static DECLARE_DELAYED_WORK(poll_pkg_cstate_work, poll_pkg_cstate);
+static void poll_pkg_cstate(struct work_struct *dummy)
+{
+ static u64 msr_last;
+ static u64 tsc_last;
+ static unsigned long jiffies_last;
+
+ u64 msr_now;
+ unsigned long jiffies_now;
+ u64 tsc_now;
+
+ msr_now = pkg_state_counter();
+ rdtscll(tsc_now);
+ jiffies_now = jiffies;
+
+ /* calculate pkg cstate vs tsc ratio */
+ if (!msr_last || !tsc_last)
+ pkg_cstate_ratio_cur = 1;
+ else {
+ if (tsc_now - tsc_last)
+ pkg_cstate_ratio_cur = 100 * (msr_now - msr_last)/
+ (tsc_now - tsc_last);
+ }
+
+ /* update record */
+ msr_last = msr_now;
+ jiffies_last = jiffies_now;
+ tsc_last = tsc_now;
+
+ if (clamping)
+ schedule_delayed_work(&poll_pkg_cstate_work, HZ);
+}
+
+static int start_power_clamp(void)
+{
+ unsigned long cpu;
+ struct task_struct *thread;
+
+ /* check if pkg cstate counter is completely 0, abort in this case */
+ if (!pkg_state_counter()) {
+ pr_err("pkg cstate counter not functional, abort\n");
+ return -EINVAL;
+ }
+
+ set_target_ratio = clamp(set_target_ratio, 0U, MAX_TARGET_RATIO);
+ /* prevent cpu hotplug */
+ get_online_cpus();
+
+ /* prefer BSP */
+ control_cpu = 0;
+ if (!cpu_online(control_cpu))
+ control_cpu = smp_processor_id();
+
+ clamping = 1;
+ schedule_delayed_work(&poll_pkg_cstate_work, 0);
+
+ /* start one thread per online cpu */
+ for_each_online_cpu(cpu) {
+ struct task_struct **p =
+ per_cpu_ptr(powerclamp_thread, cpu);
+
+ thread = kthread_create_on_node(clamp_thread,
+ (void *) cpu,
+ cpu_to_node(cpu),
+ "kidle_inject/%ld", cpu);
+ /* bind to cpu here */
+ if (likely(!IS_ERR(thread))) {
+ kthread_bind(thread, cpu);
+ wake_up_process(thread);
+ *p = thread;
+ }
+
+ }
+ put_online_cpus();
+
+ return 0;
+}
+
+static void end_power_clamp(void)
+{
+ int i;
+ struct task_struct *thread;
+
+ clamping = 0;
+ /*
+ * make clamping visible to other cpus and give per cpu clamping threads
+ * sometime to exit, or gets killed later.
+ */
+ smp_mb();
+ msleep(20);
+ if (bitmap_weight(cpu_clamping_mask, num_possible_cpus())) {
+ for_each_set_bit(i, cpu_clamping_mask, num_possible_cpus()) {
+ pr_debug("clamping thread for cpu %d alive, kill\n", i);
+ thread = *per_cpu_ptr(powerclamp_thread, i);
+ kthread_stop(thread);
+ }
+ }
+}
+
+static int powerclamp_cpu_callback(struct notifier_block *nfb,
+ unsigned long action, void *hcpu)
+{
+ unsigned long cpu = (unsigned long)hcpu;
+ struct task_struct *thread;
+ struct task_struct **percpu_thread =
+ per_cpu_ptr(powerclamp_thread, cpu);
+
+ if (!clamping)
+ goto exit_ok;
+
+ switch (action) {
+ case CPU_ONLINE:
+ thread = kthread_create_on_node(clamp_thread,
+ (void *) cpu,
+ cpu_to_node(cpu),
+ "kidle_inject/%lu", cpu);
+ if (likely(!IS_ERR(thread))) {
+ kthread_bind(thread, cpu);
+ wake_up_process(thread);
+ *percpu_thread = thread;
+ }
+ /* prefer BSP as controlling CPU */
+ if (cpu == 0) {
+ control_cpu = 0;
+ smp_mb();
+ }
+ break;
+ case CPU_DEAD:
+ if (test_bit(cpu, cpu_clamping_mask)) {
+ pr_err("cpu %lu dead but powerclamping thread is not\n",
+ cpu);
+ kthread_stop(*percpu_thread);
+ }
+ if (cpu == control_cpu) {
+ control_cpu = smp_processor_id();
+ smp_mb();
+ }
+ }
+
+exit_ok:
+ return NOTIFY_OK;
+}
+
+static struct notifier_block powerclamp_cpu_notifier = {
+ .notifier_call = powerclamp_cpu_callback,
+};
+
+static int powerclamp_get_max_state(struct thermal_cooling_device *cdev,
+ unsigned long *state)
+{
+ *state = MAX_TARGET_RATIO;
+
+ return 0;
+}
+
+static int powerclamp_get_cur_state(struct thermal_cooling_device *cdev,
+ unsigned long *state)
+{
+ if (clamping)
+ *state = pkg_cstate_ratio_cur;
+ else
+ /* to save power, do not poll idle ratio while not clamping */
+ *state = -1; /* indicates invalid state */
+
+ return 0;
+}
+
+static int powerclamp_set_cur_state(struct thermal_cooling_device *cdev,
+ unsigned long new_target_ratio)
+{
+ int ret = 0;
+
+ new_target_ratio = clamp(new_target_ratio, 0UL,
+ (unsigned long) (MAX_TARGET_RATIO-1));
+ if (set_target_ratio == 0 && new_target_ratio > 0) {
+ pr_info("Start idle injection to reduce power\n");
+ set_target_ratio = new_target_ratio;
+ ret = start_power_clamp();
+ goto exit_set;
+ } else if (set_target_ratio > 0 && new_target_ratio == 0) {
+ pr_info("Stop forced idle injection\n");
+ set_target_ratio = 0;
+ end_power_clamp();
+ } else /* adjust currently running */ {
+ set_target_ratio = new_target_ratio;
+ /* make new set_target_ratio visible to other cpus */
+ smp_mb();
+ }
+
+exit_set:
+ return ret;
+}
+
+/* bind to generic thermal layer as cooling device*/
+static struct thermal_cooling_device_ops powerclamp_cooling_ops = {
+ .get_max_state = powerclamp_get_max_state,
+ .get_cur_state = powerclamp_get_cur_state,
+ .set_cur_state = powerclamp_set_cur_state,
+};
+
+/* runs on Nehalem and later */
+static const struct x86_cpu_id intel_powerclamp_ids[] = {
+ { X86_VENDOR_INTEL, 6, 0x1a},
+ { X86_VENDOR_INTEL, 6, 0x1c},
+ { X86_VENDOR_INTEL, 6, 0x1e},
+ { X86_VENDOR_INTEL, 6, 0x1f},
+ { X86_VENDOR_INTEL, 6, 0x25},
+ { X86_VENDOR_INTEL, 6, 0x26},
+ { X86_VENDOR_INTEL, 6, 0x2a},
+ { X86_VENDOR_INTEL, 6, 0x2c},
+ { X86_VENDOR_INTEL, 6, 0x2d},
+ { X86_VENDOR_INTEL, 6, 0x2e},
+ { X86_VENDOR_INTEL, 6, 0x2f},
+ { X86_VENDOR_INTEL, 6, 0x3a},
+ {}
+};
+MODULE_DEVICE_TABLE(x86cpu, intel_powerclamp_ids);
+
+static int powerclamp_probe(void)
+{
+ if (!x86_match_cpu(intel_powerclamp_ids)) {
+ pr_err("Intel powerclamp does not run on family %d model %d\n",
+ boot_cpu_data.x86, boot_cpu_data.x86_model);
+ return -ENODEV;
+ }
+ if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC) ||
+ !boot_cpu_has(X86_FEATURE_CONSTANT_TSC) ||
+ !boot_cpu_has(X86_FEATURE_MWAIT) ||
+ !boot_cpu_has(X86_FEATURE_ARAT))
+ return -ENODEV;
+
+ /* find the deepest mwait value */
+ find_target_mwait();
+
+ return 0;
+}
+
+static int powerclamp_debug_show(struct seq_file *m, void *unused)
+{
+ int i = 0;
+
+ seq_printf(m, "controlling cpu: %d\n", control_cpu);
+ seq_printf(m, "pct confidence steady dynamic (compensation)\n");
+ for (i = 0; i < MAX_TARGET_RATIO; i++) {
+ seq_printf(m, "%d\t%lu\t%lu\t%lu\n",
+ i,
+ cal_data[i].confidence,
+ cal_data[i].steady_comp,
+ cal_data[i].dynamic_comp);
+ }
+
+ return 0;
+}
+
+static int powerclamp_debug_open(struct inode *inode,
+ struct file *file)
+{
+ return single_open(file, powerclamp_debug_show, inode->i_private);
+}
+
+static const struct file_operations powerclamp_debug_fops = {
+ .open = powerclamp_debug_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = single_release,
+ .owner = THIS_MODULE,
+};
+
+static inline void powerclamp_create_debug_files(void)
+{
+ debug_dir = debugfs_create_dir("intel_powerclamp", NULL);
+ if (!debug_dir)
+ return;
+
+ if (!debugfs_create_file("powerclamp_calib", S_IRUGO, debug_dir,
+ cal_data, &powerclamp_debug_fops))
+ goto file_error;
+
+ return;
+
+file_error:
+ debugfs_remove_recursive(debug_dir);
+}
+
+static int powerclamp_init(void)
+{
+ int retval;
+ int bitmap_size;
+
+ bitmap_size = BITS_TO_LONGS(num_possible_cpus()) * sizeof(long);
+ cpu_clamping_mask = kzalloc(bitmap_size, GFP_KERNEL);
+ if (!cpu_clamping_mask)
+ return -ENOMEM;
+
+ /* probe cpu features and ids here */
+ retval = powerclamp_probe();
+ if (retval)
+ return retval;
+ /* set default limit, maybe adjusted during runtime based on feedback */
+ window_size = 2;
+ register_hotcpu_notifier(&powerclamp_cpu_notifier);
+ powerclamp_thread = alloc_percpu(struct task_struct *);
+ cooling_dev = thermal_cooling_device_register("intel_powerclamp", NULL,
+ &powerclamp_cooling_ops);
+ if (IS_ERR(cooling_dev))
+ return -ENODEV;
+
+ if (!duration)
+ duration = jiffies_to_msecs(DEFAULT_DURATION_JIFFIES);
+ powerclamp_create_debug_files();
+
+ return 0;
+}
+module_init(powerclamp_init);
+
+static void powerclamp_exit(void)
+{
+ unregister_hotcpu_notifier(&powerclamp_cpu_notifier);
+ end_power_clamp();
+ free_percpu(powerclamp_thread);
+ thermal_cooling_device_unregister(cooling_dev);
+ kfree(cpu_clamping_mask);
+
+ cancel_delayed_work_sync(&poll_pkg_cstate_work);
+ debugfs_remove_recursive(debug_dir);
+}
+module_exit(powerclamp_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Arjan van de Ven <arjan@linux.intel.com>");
+MODULE_AUTHOR("Jacob Pan <jacob.jun.pan@linux.intel.com>");
+MODULE_DESCRIPTION("Package Level C-state Idle Injection for Intel CPUs");