intel_idle: native hardware cpuidle driver for latest Intel processors
This EXPERIMENTAL driver supersedes acpi_idle on
Intel Atom Processors, Intel Core i3/i5/i7 Processors
and associated Intel Xeon processors.
It does not support the Intel Core2 processor or earlier.
For kernels configured with ACPI, CONFIG_INTEL_IDLE=y
allows intel_idle to probe before the ACPI processor driver.
Booting with "intel_idle.max_cstate=0" disables intel_idle
and the system will fall back on ACPI's "acpi_idle".
Typical Linux distributions load ACPI processor module early,
making CONFIG_INTEL_IDLE=m not easily useful on ACPI platforms.
intel_idle probes all processors at module_init time.
Processors that are hot-added later will be limited
to using C1 in idle.
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
new file mode 100755
index 0000000..54f0fb4
--- /dev/null
+++ b/drivers/idle/intel_idle.c
@@ -0,0 +1,461 @@
+/*
+ * intel_idle.c - native hardware idle loop for modern Intel processors
+ *
+ * Copyright (c) 2010, Intel Corporation.
+ * Len Brown <len.brown@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.
+ */
+
+/*
+ * intel_idle is a cpuidle driver that loads on specific Intel processors
+ * in lieu of the legacy ACPI processor_idle driver. The intent is to
+ * make Linux more efficient on these processors, as intel_idle knows
+ * more than ACPI, as well as make Linux more immune to ACPI BIOS bugs.
+ */
+
+/*
+ * Design Assumptions
+ *
+ * All CPUs have same idle states as boot CPU
+ *
+ * Chipset BM_STS (bus master status) bit is a NOP
+ * for preventing entry into deep C-stats
+ */
+
+/*
+ * Known limitations
+ *
+ * The driver currently initializes for_each_online_cpu() upon modprobe.
+ * It it unaware of subsequent processors hot-added to the system.
+ * This means that if you boot with maxcpus=n and later online
+ * processors above n, those processors will use C1 only.
+ *
+ * ACPI has a .suspend hack to turn off deep c-statees during suspend
+ * to avoid complications with the lapic timer workaround.
+ * Have not seen issues with suspend, but may need same workaround here.
+ *
+ * There is currently no kernel-based automatic probing/loading mechanism
+ * if the driver is built as a module.
+ */
+
+/* un-comment DEBUG to enable pr_debug() statements */
+#define DEBUG
+
+#include <linux/kernel.h>
+#include <linux/cpuidle.h>
+#include <linux/clockchips.h>
+#include <linux/hrtimer.h> /* ktime_get_real() */
+#include <trace/events/power.h>
+#include <linux/sched.h>
+
+#define INTEL_IDLE_VERSION "0.4"
+#define PREFIX "intel_idle: "
+
+#define MWAIT_SUBSTATE_MASK (0xf)
+#define MWAIT_CSTATE_MASK (0xf)
+#define MWAIT_SUBSTATE_SIZE (4)
+#define MWAIT_MAX_NUM_CSTATES 8
+#define CPUID_MWAIT_LEAF (5)
+#define CPUID5_ECX_EXTENSIONS_SUPPORTED (0x1)
+#define CPUID5_ECX_INTERRUPT_BREAK (0x2)
+
+static struct cpuidle_driver intel_idle_driver = {
+ .name = "intel_idle",
+ .owner = THIS_MODULE,
+};
+/* intel_idle.max_cstate=0 disables driver */
+static int max_cstate = MWAIT_MAX_NUM_CSTATES - 1;
+static int power_policy = 7; /* 0 = max perf; 15 = max powersave */
+
+static unsigned int substates;
+static int (*choose_substate)(int);
+
+/* Reliable LAPIC Timer States, bit 1 for C1 etc. */
+static unsigned int lapic_timer_reliable_states;
+
+static struct cpuidle_device *intel_idle_cpuidle_devices;
+static int intel_idle(struct cpuidle_device *dev, struct cpuidle_state *state);
+
+static struct cpuidle_state *cpuidle_state_table;
+
+/*
+ * States are indexed by the cstate number,
+ * which is also the index into the MWAIT hint array.
+ * Thus C0 is a dummy.
+ */
+static struct cpuidle_state nehalem_cstates[MWAIT_MAX_NUM_CSTATES] = {
+ { /* MWAIT C0 */ },
+ { /* MWAIT C1 */
+ .name = "NHM-C1",
+ .desc = "MWAIT 0x00",
+ .driver_data = (void *) 0x00,
+ .flags = CPUIDLE_FLAG_TIME_VALID,
+ .exit_latency = 3,
+ .power_usage = 1000,
+ .target_residency = 6,
+ .enter = &intel_idle },
+ { /* MWAIT C2 */
+ .name = "NHM-C3",
+ .desc = "MWAIT 0x10",
+ .driver_data = (void *) 0x10,
+ .flags = CPUIDLE_FLAG_TIME_VALID,
+ .exit_latency = 20,
+ .power_usage = 500,
+ .target_residency = 80,
+ .enter = &intel_idle },
+ { /* MWAIT C3 */
+ .name = "NHM-C6",
+ .desc = "MWAIT 0x20",
+ .driver_data = (void *) 0x20,
+ .flags = CPUIDLE_FLAG_TIME_VALID,
+ .exit_latency = 200,
+ .power_usage = 350,
+ .target_residency = 800,
+ .enter = &intel_idle },
+};
+
+static struct cpuidle_state atom_cstates[MWAIT_MAX_NUM_CSTATES] = {
+ { /* MWAIT C0 */ },
+ { /* MWAIT C1 */
+ .name = "ATM-C1",
+ .desc = "MWAIT 0x00",
+ .driver_data = (void *) 0x00,
+ .flags = CPUIDLE_FLAG_TIME_VALID,
+ .exit_latency = 1,
+ .power_usage = 1000,
+ .target_residency = 4,
+ .enter = &intel_idle },
+ { /* MWAIT C2 */
+ .name = "ATM-C2",
+ .desc = "MWAIT 0x10",
+ .driver_data = (void *) 0x10,
+ .flags = CPUIDLE_FLAG_TIME_VALID,
+ .exit_latency = 20,
+ .power_usage = 500,
+ .target_residency = 80,
+ .enter = &intel_idle },
+ { /* MWAIT C3 */ },
+ { /* MWAIT C4 */
+ .name = "ATM-C4",
+ .desc = "MWAIT 0x30",
+ .driver_data = (void *) 0x30,
+ .flags = CPUIDLE_FLAG_TIME_VALID,
+ .exit_latency = 100,
+ .power_usage = 250,
+ .target_residency = 400,
+ .enter = &intel_idle },
+ { /* MWAIT C5 */ },
+ { /* MWAIT C6 */
+ .name = "ATM-C6",
+ .desc = "MWAIT 0x40",
+ .driver_data = (void *) 0x40,
+ .flags = CPUIDLE_FLAG_TIME_VALID,
+ .exit_latency = 200,
+ .power_usage = 150,
+ .target_residency = 800,
+ .enter = NULL }, /* disabled */
+};
+
+/*
+ * choose_tunable_substate()
+ *
+ * Run-time decision on which C-state substate to invoke
+ * If power_policy = 0, choose shallowest substate (0)
+ * If power_policy = 15, choose deepest substate
+ * If power_policy = middle, choose middle substate etc.
+ */
+static int choose_tunable_substate(int cstate)
+{
+ unsigned int num_substates;
+ unsigned int substate_choice;
+
+ power_policy &= 0xF; /* valid range: 0-15 */
+ cstate &= 7; /* valid range: 0-7 */
+
+ num_substates = (substates >> ((cstate) * 4)) & MWAIT_SUBSTATE_MASK;
+
+ if (num_substates <= 1)
+ return 0;
+
+ substate_choice = ((power_policy + (power_policy + 1) *
+ (num_substates - 1)) / 16);
+
+ return substate_choice;
+}
+
+/*
+ * choose_zero_substate()
+ */
+static int choose_zero_substate(int cstate)
+{
+ return 0;
+}
+
+/**
+ * intel_idle
+ * @dev: cpuidle_device
+ * @state: cpuidle state
+ *
+ */
+static int intel_idle(struct cpuidle_device *dev, struct cpuidle_state *state)
+{
+ unsigned long ecx = 1; /* break on interrupt flag */
+ unsigned long eax = (unsigned long)cpuidle_get_statedata(state);
+ unsigned int cstate;
+ ktime_t kt_before, kt_after;
+ s64 usec_delta;
+ int cpu = smp_processor_id();
+
+ cstate = (((eax) >> MWAIT_SUBSTATE_SIZE) & MWAIT_CSTATE_MASK) + 1;
+
+ eax = eax + (choose_substate)(cstate);
+
+ local_irq_disable();
+
+ if (!(lapic_timer_reliable_states & (1 << (cstate))))
+ clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);
+
+ kt_before = ktime_get_real();
+
+ stop_critical_timings();
+#ifndef MODULE
+ trace_power_start(POWER_CSTATE, (eax >> 4) + 1);
+#endif
+ if (!need_resched()) {
+
+ __monitor((void *)¤t_thread_info()->flags, 0, 0);
+ smp_mb();
+ if (!need_resched())
+ __mwait(eax, ecx);
+ }
+
+ start_critical_timings();
+
+ kt_after = ktime_get_real();
+ usec_delta = ktime_to_us(ktime_sub(kt_after, kt_before));
+
+ local_irq_enable();
+
+ if (!(lapic_timer_reliable_states & (1 << (cstate))))
+ clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);
+
+ return usec_delta;
+}
+
+/*
+ * intel_idle_probe()
+ */
+static int intel_idle_probe(void)
+{
+ unsigned int eax, ebx, ecx, edx;
+
+ if (max_cstate == 0) {
+ pr_debug(PREFIX "disabled\n");
+ return -EPERM;
+ }
+
+ if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
+ return -ENODEV;
+
+ if (!boot_cpu_has(X86_FEATURE_MWAIT))
+ return -ENODEV;
+
+ if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
+ return -ENODEV;
+
+ cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx);
+
+ if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) ||
+ !(ecx & CPUID5_ECX_INTERRUPT_BREAK))
+ return -ENODEV;
+#ifdef DEBUG
+ if (substates == 0) /* can over-ride via modparam */
+#endif
+ substates = edx;
+
+ pr_debug(PREFIX "MWAIT substates: 0x%x\n", substates);
+
+ if (boot_cpu_has(X86_FEATURE_ARAT)) /* Always Reliable APIC Timer */
+ lapic_timer_reliable_states = 0xFFFFFFFF;
+
+ if (boot_cpu_data.x86 != 6) /* family 6 */
+ return -ENODEV;
+
+ switch (boot_cpu_data.x86_model) {
+
+ case 0x1A: /* Core i7, Xeon 5500 series */
+ case 0x1E: /* Core i7 and i5 Processor - Lynnfield Jasper Forest */
+ case 0x1F: /* Core i7 and i5 Processor - Nehalem */
+ case 0x2E: /* Nehalem-EX Xeon */
+ lapic_timer_reliable_states = (1 << 1); /* C1 */
+
+ case 0x25: /* Westmere */
+ case 0x2C: /* Westmere */
+ cpuidle_state_table = nehalem_cstates;
+ choose_substate = choose_tunable_substate;
+ break;
+
+ case 0x1C: /* 28 - Atom Processor */
+ lapic_timer_reliable_states = (1 << 2) | (1 << 1); /* C2, C1 */
+ cpuidle_state_table = atom_cstates;
+ choose_substate = choose_zero_substate;
+ break;
+#ifdef FUTURE_USE
+ case 0x17: /* 23 - Core 2 Duo */
+ lapic_timer_reliable_states = (1 << 2) | (1 << 1); /* C2, C1 */
+#endif
+
+ default:
+ pr_debug(PREFIX "does not run on family %d model %d\n",
+ boot_cpu_data.x86, boot_cpu_data.x86_model);
+ return -ENODEV;
+ }
+
+ pr_debug(PREFIX "v" INTEL_IDLE_VERSION
+ " model 0x%X\n", boot_cpu_data.x86_model);
+
+ pr_debug(PREFIX "lapic_timer_reliable_states 0x%x\n",
+ lapic_timer_reliable_states);
+ return 0;
+}
+
+/*
+ * intel_idle_cpuidle_devices_uninit()
+ * unregister, free cpuidle_devices
+ */
+static void intel_idle_cpuidle_devices_uninit(void)
+{
+ int i;
+ struct cpuidle_device *dev;
+
+ for_each_online_cpu(i) {
+ dev = per_cpu_ptr(intel_idle_cpuidle_devices, i);
+ cpuidle_unregister_device(dev);
+ }
+
+ free_percpu(intel_idle_cpuidle_devices);
+ return;
+}
+/*
+ * intel_idle_cpuidle_devices_init()
+ * allocate, initialize, register cpuidle_devices
+ */
+static int intel_idle_cpuidle_devices_init(void)
+{
+ int i, cstate;
+ struct cpuidle_device *dev;
+
+ intel_idle_cpuidle_devices = alloc_percpu(struct cpuidle_device);
+ if (intel_idle_cpuidle_devices == NULL)
+ return -ENOMEM;
+
+ for_each_online_cpu(i) {
+ dev = per_cpu_ptr(intel_idle_cpuidle_devices, i);
+
+ dev->state_count = 1;
+
+ for (cstate = 1; cstate < MWAIT_MAX_NUM_CSTATES; ++cstate) {
+ int num_substates;
+
+ if (cstate > max_cstate) {
+ printk(PREFIX "max_cstate %d reached\n",
+ max_cstate);
+ break;
+ }
+
+ /* does the state exist in CPUID.MWAIT? */
+ num_substates = (substates >> ((cstate) * 4))
+ & MWAIT_SUBSTATE_MASK;
+ if (num_substates == 0)
+ continue;
+ /* is the state not enabled? */
+ if (cpuidle_state_table[cstate].enter == NULL) {
+ /* does the driver not know about the state? */
+ if (*cpuidle_state_table[cstate].name == '\0')
+ pr_debug(PREFIX "unaware of model 0x%x"
+ " MWAIT %d please"
+ " contact lenb@kernel.org",
+ boot_cpu_data.x86_model, cstate);
+ continue;
+ }
+
+ if ((cstate > 2) &&
+ !boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
+ mark_tsc_unstable("TSC halts in idle"
+ " states deeper than C2");
+
+ dev->states[dev->state_count] = /* structure copy */
+ cpuidle_state_table[cstate];
+
+ dev->state_count += 1;
+ }
+
+ dev->cpu = i;
+ if (cpuidle_register_device(dev)) {
+ pr_debug(PREFIX "cpuidle_register_device %d failed!\n",
+ i);
+ intel_idle_cpuidle_devices_uninit();
+ return -EIO;
+ }
+ }
+
+ return 0;
+}
+
+
+static int __init intel_idle_init(void)
+{
+ int retval;
+
+ retval = intel_idle_probe();
+ if (retval)
+ return retval;
+
+ retval = cpuidle_register_driver(&intel_idle_driver);
+ if (retval) {
+ printk(KERN_DEBUG PREFIX "intel_idle yielding to %s",
+ cpuidle_get_driver()->name);
+ return retval;
+ }
+
+ retval = intel_idle_cpuidle_devices_init();
+ if (retval) {
+ cpuidle_unregister_driver(&intel_idle_driver);
+ return retval;
+ }
+
+ return 0;
+}
+
+static void __exit intel_idle_exit(void)
+{
+ intel_idle_cpuidle_devices_uninit();
+ cpuidle_unregister_driver(&intel_idle_driver);
+
+ return;
+}
+
+module_init(intel_idle_init);
+module_exit(intel_idle_exit);
+
+module_param(power_policy, int, 0644);
+module_param(max_cstate, int, 0444);
+#ifdef DEBUG
+module_param(substates, int, 0444);
+#endif
+
+MODULE_AUTHOR("Len Brown <len.brown@intel.com>");
+MODULE_DESCRIPTION("Cpuidle driver for Intel Hardware v" INTEL_IDLE_VERSION);
+MODULE_LICENSE("GPL");
