linux/drivers/cpuidle/cpuidle-powernv.c
Aboorva Devarajan 5ddcc03a07 powerpc/cpuidle: Set CPUIDLE_FLAG_POLLING for snooze state
During the comparative study of cpuidle governors, it is noticed that the
menu governor does not select CEDE state in some scenarios even though when
the sleep duration of the CPU exceeds the target residency of the CEDE idle
state this is because the CPU exits the snooze "polling" state when snooze
time limit is reached in the snooze_loop(), which is not a real wake up
and it just means that the polling state selection was not adequate.

cpuidle governors rely on CPUIDLE_FLAG_POLLING flag to be set for the
polling states to handle the condition mentioned above.

Hence, set the CPUIDLE_FLAG_POLLING flag for snooze state (polling state)
in powerpc arch to make the cpuidle governor work as expected.

Reference Commits:

- Timeout enabled for snooze state:
  commit 78eaa10f02
  ("cpuidle: powernv/pseries: Auto-promotion of snooze to deeper idle state")

- commit dc2251bf98
  ("cpuidle: Eliminate the CPUIDLE_DRIVER_STATE_START symbol")

- Fix wakeup stats in governor for polling states
  commit 5f26bdceb9
  ("cpuidle: menu: Fix wakeup statistics updates for polling state")

Signed-off-by: Aboorva Devarajan <aboorvad@linux.vnet.ibm.com>
Tested-by: Vishal Chourasia <vishalc@linux.vnet.ibm.com>
Reviewed-by: Vaidyanathan Srinivasan <svaidy@linux.ibm.com>
Reviewed-by: Vishal Chourasia <vishalc@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20221114145611.37669-1-aboorvad@linux.vnet.ibm.com
2022-12-06 23:18:19 +11:00

407 lines
10 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* cpuidle-powernv - idle state cpuidle driver.
* Adapted from drivers/cpuidle/cpuidle-pseries
*
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/moduleparam.h>
#include <linux/cpuidle.h>
#include <linux/cpu.h>
#include <linux/notifier.h>
#include <linux/clockchips.h>
#include <linux/of.h>
#include <linux/slab.h>
#include <asm/machdep.h>
#include <asm/firmware.h>
#include <asm/opal.h>
#include <asm/runlatch.h>
#include <asm/cpuidle.h>
/*
* Expose only those Hardware idle states via the cpuidle framework
* that have latency value below POWERNV_THRESHOLD_LATENCY_NS.
*/
#define POWERNV_THRESHOLD_LATENCY_NS 200000
static struct cpuidle_driver powernv_idle_driver = {
.name = "powernv_idle",
.owner = THIS_MODULE,
};
static int max_idle_state __read_mostly;
static struct cpuidle_state *cpuidle_state_table __read_mostly;
struct stop_psscr_table {
u64 val;
u64 mask;
};
static struct stop_psscr_table stop_psscr_table[CPUIDLE_STATE_MAX] __read_mostly;
static u64 default_snooze_timeout __read_mostly;
static bool snooze_timeout_en __read_mostly;
static u64 get_snooze_timeout(struct cpuidle_device *dev,
struct cpuidle_driver *drv,
int index)
{
int i;
if (unlikely(!snooze_timeout_en))
return default_snooze_timeout;
for (i = index + 1; i < drv->state_count; i++) {
if (dev->states_usage[i].disable)
continue;
return drv->states[i].target_residency * tb_ticks_per_usec;
}
return default_snooze_timeout;
}
static int snooze_loop(struct cpuidle_device *dev,
struct cpuidle_driver *drv,
int index)
{
u64 snooze_exit_time;
set_thread_flag(TIF_POLLING_NRFLAG);
local_irq_enable();
snooze_exit_time = get_tb() + get_snooze_timeout(dev, drv, index);
dev->poll_time_limit = false;
ppc64_runlatch_off();
HMT_very_low();
while (!need_resched()) {
if (likely(snooze_timeout_en) && get_tb() > snooze_exit_time) {
/*
* Task has not woken up but we are exiting the polling
* loop anyway. Require a barrier after polling is
* cleared to order subsequent test of need_resched().
*/
clear_thread_flag(TIF_POLLING_NRFLAG);
dev->poll_time_limit = true;
smp_mb();
break;
}
}
HMT_medium();
ppc64_runlatch_on();
clear_thread_flag(TIF_POLLING_NRFLAG);
local_irq_disable();
return index;
}
static int nap_loop(struct cpuidle_device *dev,
struct cpuidle_driver *drv,
int index)
{
power7_idle_type(PNV_THREAD_NAP);
return index;
}
/* Register for fastsleep only in oneshot mode of broadcast */
#ifdef CONFIG_TICK_ONESHOT
static int fastsleep_loop(struct cpuidle_device *dev,
struct cpuidle_driver *drv,
int index)
{
unsigned long old_lpcr = mfspr(SPRN_LPCR);
unsigned long new_lpcr;
if (unlikely(system_state < SYSTEM_RUNNING))
return index;
new_lpcr = old_lpcr;
/* Do not exit powersave upon decrementer as we've setup the timer
* offload.
*/
new_lpcr &= ~LPCR_PECE1;
mtspr(SPRN_LPCR, new_lpcr);
power7_idle_type(PNV_THREAD_SLEEP);
mtspr(SPRN_LPCR, old_lpcr);
return index;
}
#endif
static int stop_loop(struct cpuidle_device *dev,
struct cpuidle_driver *drv,
int index)
{
arch300_idle_type(stop_psscr_table[index].val,
stop_psscr_table[index].mask);
return index;
}
/*
* States for dedicated partition case.
*/
static struct cpuidle_state powernv_states[CPUIDLE_STATE_MAX] = {
{ /* Snooze */
.name = "snooze",
.desc = "snooze",
.exit_latency = 0,
.target_residency = 0,
.enter = snooze_loop,
.flags = CPUIDLE_FLAG_POLLING },
};
static int powernv_cpuidle_cpu_online(unsigned int cpu)
{
struct cpuidle_device *dev = per_cpu(cpuidle_devices, cpu);
if (dev && cpuidle_get_driver()) {
cpuidle_pause_and_lock();
cpuidle_enable_device(dev);
cpuidle_resume_and_unlock();
}
return 0;
}
static int powernv_cpuidle_cpu_dead(unsigned int cpu)
{
struct cpuidle_device *dev = per_cpu(cpuidle_devices, cpu);
if (dev && cpuidle_get_driver()) {
cpuidle_pause_and_lock();
cpuidle_disable_device(dev);
cpuidle_resume_and_unlock();
}
return 0;
}
/*
* powernv_cpuidle_driver_init()
*/
static int powernv_cpuidle_driver_init(void)
{
int idle_state;
struct cpuidle_driver *drv = &powernv_idle_driver;
drv->state_count = 0;
for (idle_state = 0; idle_state < max_idle_state; ++idle_state) {
/* Is the state not enabled? */
if (cpuidle_state_table[idle_state].enter == NULL)
continue;
drv->states[drv->state_count] = /* structure copy */
cpuidle_state_table[idle_state];
drv->state_count += 1;
}
/*
* On the PowerNV platform cpu_present may be less than cpu_possible in
* cases when firmware detects the CPU, but it is not available to the
* OS. If CONFIG_HOTPLUG_CPU=n, then such CPUs are not hotplugable at
* run time and hence cpu_devices are not created for those CPUs by the
* generic topology_init().
*
* drv->cpumask defaults to cpu_possible_mask in
* __cpuidle_driver_init(). This breaks cpuidle on PowerNV where
* cpu_devices are not created for CPUs in cpu_possible_mask that
* cannot be hot-added later at run time.
*
* Trying cpuidle_register_device() on a CPU without a cpu_device is
* incorrect, so pass a correct CPU mask to the generic cpuidle driver.
*/
drv->cpumask = (struct cpumask *)cpu_present_mask;
return 0;
}
static inline void add_powernv_state(int index, const char *name,
unsigned int flags,
int (*idle_fn)(struct cpuidle_device *,
struct cpuidle_driver *,
int),
unsigned int target_residency,
unsigned int exit_latency,
u64 psscr_val, u64 psscr_mask)
{
strscpy(powernv_states[index].name, name, CPUIDLE_NAME_LEN);
strscpy(powernv_states[index].desc, name, CPUIDLE_NAME_LEN);
powernv_states[index].flags = flags;
powernv_states[index].target_residency = target_residency;
powernv_states[index].exit_latency = exit_latency;
powernv_states[index].enter = idle_fn;
/* For power8 and below psscr_* will be 0 */
stop_psscr_table[index].val = psscr_val;
stop_psscr_table[index].mask = psscr_mask;
}
extern u32 pnv_get_supported_cpuidle_states(void);
static int powernv_add_idle_states(void)
{
int nr_idle_states = 1; /* Snooze */
int dt_idle_states;
u32 has_stop_states = 0;
int i;
u32 supported_flags = pnv_get_supported_cpuidle_states();
/* Currently we have snooze statically defined */
if (nr_pnv_idle_states <= 0) {
pr_warn("cpuidle-powernv : Only Snooze is available\n");
goto out;
}
/* TODO: Count only states which are eligible for cpuidle */
dt_idle_states = nr_pnv_idle_states;
/*
* Since snooze is used as first idle state, max idle states allowed is
* CPUIDLE_STATE_MAX -1
*/
if (nr_pnv_idle_states > CPUIDLE_STATE_MAX - 1) {
pr_warn("cpuidle-powernv: discovered idle states more than allowed");
dt_idle_states = CPUIDLE_STATE_MAX - 1;
}
/*
* If the idle states use stop instruction, probe for psscr values
* and psscr mask which are necessary to specify required stop level.
*/
has_stop_states = (pnv_idle_states[0].flags &
(OPAL_PM_STOP_INST_FAST | OPAL_PM_STOP_INST_DEEP));
for (i = 0; i < dt_idle_states; i++) {
unsigned int exit_latency, target_residency;
bool stops_timebase = false;
struct pnv_idle_states_t *state = &pnv_idle_states[i];
/*
* Skip the platform idle state whose flag isn't in
* the supported_cpuidle_states flag mask.
*/
if ((state->flags & supported_flags) != state->flags)
continue;
/*
* If an idle state has exit latency beyond
* POWERNV_THRESHOLD_LATENCY_NS then don't use it
* in cpu-idle.
*/
if (state->latency_ns > POWERNV_THRESHOLD_LATENCY_NS)
continue;
/*
* Firmware passes residency and latency values in ns.
* cpuidle expects it in us.
*/
exit_latency = DIV_ROUND_UP(state->latency_ns, 1000);
target_residency = DIV_ROUND_UP(state->residency_ns, 1000);
if (has_stop_states && !(state->valid))
continue;
if (state->flags & OPAL_PM_TIMEBASE_STOP)
stops_timebase = true;
if (state->flags & OPAL_PM_NAP_ENABLED) {
/* Add NAP state */
add_powernv_state(nr_idle_states, "Nap",
CPUIDLE_FLAG_NONE, nap_loop,
target_residency, exit_latency, 0, 0);
} else if (has_stop_states && !stops_timebase) {
add_powernv_state(nr_idle_states, state->name,
CPUIDLE_FLAG_NONE, stop_loop,
target_residency, exit_latency,
state->psscr_val,
state->psscr_mask);
}
/*
* All cpuidle states with CPUIDLE_FLAG_TIMER_STOP set must come
* within this config dependency check.
*/
#ifdef CONFIG_TICK_ONESHOT
else if (state->flags & OPAL_PM_SLEEP_ENABLED ||
state->flags & OPAL_PM_SLEEP_ENABLED_ER1) {
/* Add FASTSLEEP state */
add_powernv_state(nr_idle_states, "FastSleep",
CPUIDLE_FLAG_TIMER_STOP,
fastsleep_loop,
target_residency, exit_latency, 0, 0);
} else if (has_stop_states && stops_timebase) {
add_powernv_state(nr_idle_states, state->name,
CPUIDLE_FLAG_TIMER_STOP, stop_loop,
target_residency, exit_latency,
state->psscr_val,
state->psscr_mask);
}
#endif
else
continue;
nr_idle_states++;
}
out:
return nr_idle_states;
}
/*
* powernv_idle_probe()
* Choose state table for shared versus dedicated partition
*/
static int powernv_idle_probe(void)
{
if (cpuidle_disable != IDLE_NO_OVERRIDE)
return -ENODEV;
if (firmware_has_feature(FW_FEATURE_OPAL)) {
cpuidle_state_table = powernv_states;
/* Device tree can indicate more idle states */
max_idle_state = powernv_add_idle_states();
default_snooze_timeout = TICK_USEC * tb_ticks_per_usec;
if (max_idle_state > 1)
snooze_timeout_en = true;
} else
return -ENODEV;
return 0;
}
static int __init powernv_processor_idle_init(void)
{
int retval;
retval = powernv_idle_probe();
if (retval)
return retval;
powernv_cpuidle_driver_init();
retval = cpuidle_register(&powernv_idle_driver, NULL);
if (retval) {
printk(KERN_DEBUG "Registration of powernv driver failed.\n");
return retval;
}
retval = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
"cpuidle/powernv:online",
powernv_cpuidle_cpu_online, NULL);
WARN_ON(retval < 0);
retval = cpuhp_setup_state_nocalls(CPUHP_CPUIDLE_DEAD,
"cpuidle/powernv:dead", NULL,
powernv_cpuidle_cpu_dead);
WARN_ON(retval < 0);
printk(KERN_DEBUG "powernv_idle_driver registered\n");
return 0;
}
device_initcall(powernv_processor_idle_init);