cpuidle: Eliminate the CPUIDLE_DRIVER_STATE_START symbol
On some architectures the first (index 0) idle state is a polling
one and it doesn't really save energy, so there is the
CPUIDLE_DRIVER_STATE_START symbol allowing some pieces of
cpuidle code to avoid using that state.
However, this makes the code rather hard to follow. It is better
to explicitly avoid the polling state, so add a new cpuidle state
flag CPUIDLE_FLAG_POLLING to mark it and make the relevant code
check that flag for the first state instead of using the
CPUIDLE_DRIVER_STATE_START symbol.
In the ACPI processor driver that cannot always rely on the state
flags (like before the states table has been set up) define
a new internal symbol ACPI_IDLE_STATE_START equivalent to the
CPUIDLE_DRIVER_STATE_START one and drop the latter.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Sudeep Holla <sudeep.holla@arm.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 5c8aa9c..39a01ea 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -48,6 +48,8 @@
#define _COMPONENT ACPI_PROCESSOR_COMPONENT
ACPI_MODULE_NAME("processor_idle");
+#define ACPI_IDLE_STATE_START (IS_ENABLED(CONFIG_ARCH_HAS_CPU_RELAX) ? 1 : 0)
+
static unsigned int max_cstate __read_mostly = ACPI_PROCESSOR_MAX_POWER;
module_param(max_cstate, uint, 0000);
static unsigned int nocst __read_mostly;
@@ -761,7 +763,7 @@
if (cx->type != ACPI_STATE_C1) {
if (acpi_idle_fallback_to_c1(pr) && num_online_cpus() > 1) {
- index = CPUIDLE_DRIVER_STATE_START;
+ index = ACPI_IDLE_STATE_START;
cx = per_cpu(acpi_cstate[index], dev->cpu);
} else if (cx->type == ACPI_STATE_C3 && pr->flags.bm_check) {
if (cx->bm_sts_skip || !acpi_idle_bm_check()) {
@@ -813,7 +815,7 @@
static int acpi_processor_setup_cpuidle_cx(struct acpi_processor *pr,
struct cpuidle_device *dev)
{
- int i, count = CPUIDLE_DRIVER_STATE_START;
+ int i, count = ACPI_IDLE_STATE_START;
struct acpi_processor_cx *cx;
if (max_cstate == 0)
@@ -840,7 +842,7 @@
static int acpi_processor_setup_cstates(struct acpi_processor *pr)
{
- int i, count = CPUIDLE_DRIVER_STATE_START;
+ int i, count = ACPI_IDLE_STATE_START;
struct acpi_processor_cx *cx;
struct cpuidle_state *state;
struct cpuidle_driver *drv = &acpi_idle_driver;
@@ -1291,7 +1293,7 @@
return -EINVAL;
drv->safe_state_index = -1;
- for (i = CPUIDLE_DRIVER_STATE_START; i < CPUIDLE_STATE_MAX; i++) {
+ for (i = ACPI_IDLE_STATE_START; i < CPUIDLE_STATE_MAX; i++) {
drv->states[i].name[0] = '\0';
drv->states[i].desc[0] = '\0';
}
diff --git a/drivers/cpuidle/driver.c b/drivers/cpuidle/driver.c
index e53fb86..e942f8e 100644
--- a/drivers/cpuidle/driver.c
+++ b/drivers/cpuidle/driver.c
@@ -204,6 +204,7 @@
state->power_usage = -1;
state->enter = poll_idle;
state->disabled = false;
+ state->flags = CPUIDLE_FLAG_POLLING;
}
#else
static void poll_idle_init(struct cpuidle_driver *drv) {}
diff --git a/drivers/cpuidle/governors/ladder.c b/drivers/cpuidle/governors/ladder.c
index ac321f0..ce1a2ff 100644
--- a/drivers/cpuidle/governors/ladder.c
+++ b/drivers/cpuidle/governors/ladder.c
@@ -69,6 +69,7 @@
struct ladder_device *ldev = this_cpu_ptr(&ladder_devices);
struct ladder_device_state *last_state;
int last_residency, last_idx = ldev->last_state_idx;
+ int first_idx = drv->states[0].flags & CPUIDLE_FLAG_POLLING ? 1 : 0;
int latency_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
/* Special case when user has set very strict latency requirement */
@@ -96,13 +97,13 @@
}
/* consider demotion */
- if (last_idx > CPUIDLE_DRIVER_STATE_START &&
+ if (last_idx > first_idx &&
(drv->states[last_idx].disabled ||
dev->states_usage[last_idx].disable ||
drv->states[last_idx].exit_latency > latency_req)) {
int i;
- for (i = last_idx - 1; i > CPUIDLE_DRIVER_STATE_START; i--) {
+ for (i = last_idx - 1; i > first_idx; i--) {
if (drv->states[i].exit_latency <= latency_req)
break;
}
@@ -110,7 +111,7 @@
return i;
}
- if (last_idx > CPUIDLE_DRIVER_STATE_START &&
+ if (last_idx > first_idx &&
last_residency < last_state->threshold.demotion_time) {
last_state->stats.demotion_count++;
last_state->stats.promotion_count = 0;
@@ -133,13 +134,14 @@
struct cpuidle_device *dev)
{
int i;
+ int first_idx = drv->states[0].flags & CPUIDLE_FLAG_POLLING ? 1 : 0;
struct ladder_device *ldev = &per_cpu(ladder_devices, dev->cpu);
struct ladder_device_state *lstate;
struct cpuidle_state *state;
- ldev->last_state_idx = CPUIDLE_DRIVER_STATE_START;
+ ldev->last_state_idx = first_idx;
- for (i = CPUIDLE_DRIVER_STATE_START; i < drv->state_count; i++) {
+ for (i = first_idx; i < drv->state_count; i++) {
state = &drv->states[i];
lstate = &ldev->states[i];
@@ -151,7 +153,7 @@
if (i < drv->state_count - 1)
lstate->threshold.promotion_time = state->exit_latency;
- if (i > CPUIDLE_DRIVER_STATE_START)
+ if (i > first_idx)
lstate->threshold.demotion_time = state->exit_latency;
}
diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index 61b64c2..48eaf28 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -324,8 +324,9 @@
expected_interval = get_typical_interval(data);
expected_interval = min(expected_interval, data->next_timer_us);
- if (CPUIDLE_DRIVER_STATE_START > 0) {
- struct cpuidle_state *s = &drv->states[CPUIDLE_DRIVER_STATE_START];
+ first_idx = 0;
+ if (drv->states[0].flags & CPUIDLE_FLAG_POLLING) {
+ struct cpuidle_state *s = &drv->states[1];
unsigned int polling_threshold;
/*
@@ -336,12 +337,8 @@
polling_threshold = max_t(unsigned int, 20, s->target_residency);
if (data->next_timer_us > polling_threshold &&
latency_req > s->exit_latency && !s->disabled &&
- !dev->states_usage[CPUIDLE_DRIVER_STATE_START].disable)
- first_idx = CPUIDLE_DRIVER_STATE_START;
- else
- first_idx = CPUIDLE_DRIVER_STATE_START - 1;
- } else {
- first_idx = 0;
+ !dev->states_usage[1].disable)
+ first_idx = 1;
}
/*
diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index fc1e5d7..b58d952 100644
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -63,6 +63,7 @@
/* Idle State Flags */
#define CPUIDLE_FLAG_NONE (0x00)
+#define CPUIDLE_FLAG_POLLING (0x01) /* polling state */
#define CPUIDLE_FLAG_COUPLED (0x02) /* state applies to multiple cpus */
#define CPUIDLE_FLAG_TIMER_STOP (0x04) /* timer is stopped on this state */
@@ -250,12 +251,6 @@
{return 0;}
#endif
-#ifdef CONFIG_ARCH_HAS_CPU_RELAX
-#define CPUIDLE_DRIVER_STATE_START 1
-#else
-#define CPUIDLE_DRIVER_STATE_START 0
-#endif
-
#define CPU_PM_CPU_IDLE_ENTER(low_level_idle_enter, idx) \
({ \
int __ret; \