/*
* 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, cpu);
#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");
