// SPDX-License-Identifier: GPL-2.0
/*
* cpuidle-pseries - idle state cpuidle driver.
* Adapted from drivers/idle/intel_idle.c and
* drivers/acpi/processor_idle.c
*
*/
#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 <asm/paca.h>
#include <asm/reg.h>
#include <asm/machdep.h>
#include <asm/firmware.h>
#include <asm/runlatch.h>
#include <asm/idle.h>
#include <asm/plpar_wrappers.h>
#include <asm/rtas.h>
static struct cpuidle_driver pseries_idle_driver = {
.name = "pseries_idle",
.owner = THIS_MODULE,
};
static int max_idle_state __read_mostly;
static struct cpuidle_state *cpuidle_state_table __read_mostly;
static u64 snooze_timeout __read_mostly;
static bool snooze_timeout_en __read_mostly;
static __cpuidle
int snooze_loop(struct cpuidle_device *dev, struct cpuidle_driver *drv,
int index)
{
u64 snooze_exit_time;
set_thread_flag(TIF_POLLING_NRFLAG);
pseries_idle_prolog();
raw_local_irq_enable();
snooze_exit_time = get_tb() + snooze_timeout;
dev->poll_time_limit = false;
while (!need_resched()) {
HMT_low();
HMT_very_low();
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().
*/
dev->poll_time_limit = true;
clear_thread_flag(TIF_POLLING_NRFLAG);
smp_mb();
break;
}
}
HMT_medium();
clear_thread_flag(TIF_POLLING_NRFLAG);
raw_local_irq_disable();
pseries_idle_epilog();
return index;
}
static __cpuidle void check_and_cede_processor(void)
{
/*
* Ensure our interrupt state is properly tracked,
* also checks if no interrupt has occurred while we
* were soft-disabled
*/
if (prep_irq_for_idle()) {
cede_processor();
#ifdef CONFIG_TRACE_IRQFLAGS
/* Ensure that H_CEDE returns with IRQs on */
if (WARN_ON(!(mfmsr() & MSR_EE)))
__hard_irq_enable();
#endif
}
}
/*
* XCEDE: Extended CEDE states discovered through the
* "ibm,get-systems-parameter" RTAS call with the token
* CEDE_LATENCY_TOKEN
*/
/*
* Section 7.3.16 System Parameters Option of PAPR version 2.8.1 has a
* table with all the parameters to ibm,get-system-parameters.
* CEDE_LATENCY_TOKEN corresponds to the token value for Cede Latency
* Settings Information.
*/
#define CEDE_LATENCY_TOKEN 45
/*
* If the platform supports the cede latency settings information system
* parameter it must provide the following information in the NULL terminated
* parameter string:
*
* a. The first byte is the length “N” of each cede latency setting record minus
* one (zero indicates a length of 1 byte).
*
* b. For each supported cede latency setting a cede latency setting record
* consisting of the first “N” bytes as per the following table.
*
* -----------------------------
* | Field | Field |
* | Name | Length |
* -----------------------------
* | Cede Latency | 1 Byte |
* | Specifier Value | |
* -----------------------------
* | Maximum wakeup | |
* | latency in | 8 Bytes |
* | tb-ticks | |
* -----------------------------
* | Responsive to | |
* | external | 1 Byte |
* | interrupts | |
* -----------------------------
*
* This version has cede latency record size = 10.
*
* The structure xcede_latency_payload represents a) and b) with
* xcede_latency_record representing the table in b).
*
* xcede_latency_parameter is what gets returned by
* ibm,get-systems-parameter RTAS call when made with
* CEDE_LATENCY_TOKEN.
*
* These structures are only used to represent the data obtained by the RTAS
* call. The data is in big-endian.
*/
struct xcede_latency_record {
u8 hint;
__be64 latency_ticks;
u8 wake_on_irqs;
} __packed;
// Make space for 16 records, which "should be enough".
struct xcede_latency_payload {
u8 record_size;
struct xcede_latency_record records[16];
} __packed;
struct xcede_latency_parameter {
__be16 payload_size;
struct xcede_latency_payload payload;
u8 null_char;
} __packed;
static unsigned int nr_xcede_records;
static struct xcede_latency_parameter xcede_latency_parameter __initdata;
static int __init parse_cede_parameters(void)
{
struct xcede_latency_payload *payload;
u32 total_xcede_records_size;
u8 xcede_record_size;
u16 payload_size;
int ret, i;
ret = rtas_call(rtas_token("ibm,get-system-parameter"), 3, 1,
NULL, CEDE_LATENCY_TOKEN, __pa(&xcede_latency_parameter),
sizeof(xcede_latency_parameter));
if (ret) {
pr_err("xcede: Error parsing CEDE_LATENCY_TOKEN\n");
return ret;
}
payload_size = be16_to_cpu(xcede_latency_parameter.payload_size);
payload = &xcede_latency_parameter.payload;
xcede_record_size = payload->record_size + 1;
if (xcede_record_size != sizeof(struct xcede_latency_record)) {
pr_err("xcede: Expected record-size %lu. Observed size %u.\n",
sizeof(struct xcede_latency_record), xcede_record_size);
return -EINVAL;
}
pr_info("xcede: xcede_record_size = %d\n", xcede_record_size);
/*
* Since the payload_size includes the last NULL byte and the
* xcede_record_size, the remaining bytes correspond to array of all
* cede_latency settings.
*/
total_xcede_records_size = payload_size - 2;
nr_xcede_records = total_xcede_records_size / xcede_record_size;
for (i = 0; i < nr_xcede_records; i++) {
struct xcede_latency_record *record = &payload->records[i];
u64 latency_ticks = be64_to_cpu(record->latency_ticks);
u8 wake_on_irqs = record->wake_on_irqs;
u8 hint = record->hint;
pr_info("xcede: Record %d : hint = %u, latency = 0x%llx tb ticks, Wake-on-irq = %u\n",
i, hint, latency_ticks, wake_on_irqs);
}
return 0;
}
#define NR_DEDICATED_STATES 2 /* snooze, CEDE */
static u8 cede_latency_hint[NR_DEDICATED_STATES];
static __cpuidle
int dedicated_cede_loop(struct cpuidle_device *dev, struct cpuidle_driver *drv,
int index)
{
u8 old_latency_hint;
pseries_idle_prolog();
get_lppaca()->donate_dedicated_cpu = 1;
old_latency_hint = get_lppaca()->cede_latency_hint;
get_lppaca()->cede_latency_hint = cede_latency_hint[index];
HMT_medium();
check_and_cede_processor();
raw_local_irq_disable();
get_lppaca()->donate_dedicated_cpu = 0;
get_lppaca()->cede_latency_hint = old_latency_hint;
pseries_idle_epilog();
return index;
}
static __cpuidle
int shared_cede_loop(struct cpuidle_device *dev, struct cpuidle_driver *drv,
int index)
{
pseries_idle_prolog();
/*
* Yield the processor to the hypervisor. We return if
* an external interrupt occurs (which are driven prior
* to returning here) or if a prod occurs from another
* processor. When returning here, external interrupts
* are enabled.
*/
check_and_cede_processor();
raw_local_irq_disable();
pseries_idle_epilog();
return index;
}
/*
* States for dedicated partition case.
*/
static struct cpuidle_state dedicated_states[NR_DEDICATED_STATES] = {
{ /* Snooze */
.name = "snooze",
.desc = "snooze",
.exit_latency = 0,
.target_residency = 0,
.enter = &snooze_loop,
.flags = CPUIDLE_FLAG_POLLING },
{ /* CEDE */
.name = "CEDE",
.desc = "CEDE",
.exit_latency = 10,
.target_residency = 100,
.enter = &dedicated_cede_loop },
};
/*
* States for shared partition case.
*/
static struct cpuidle_state shared_states[] = {
{ /* Snooze */
.name = "snooze",
.desc = "snooze",
.exit_latency = 0,
.target_residency = 0,
.enter = &snooze_loop,
.flags = CPUIDLE_FLAG_POLLING },
{ /* Shared Cede */
.name = "Shared Cede",
.desc = "Shared Cede",
.exit_latency = 10,
.target_residency = 100,
.enter = &shared_cede_loop },
};
static int pseries_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 pseries_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;
}
/*
* pseries_cpuidle_driver_init()
*/
static int pseries_cpuidle_driver_init(void)
{
int idle_state;
struct cpuidle_driver *drv = &pseries_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;
}
return 0;
}
static void __init fixup_cede0_latency(void)
{
struct xcede_latency_payload *payload;
u64 min_xcede_latency_us = UINT_MAX;
int i;
if (parse_cede_parameters())
return;
pr_info("cpuidle: Skipping the %d Extended CEDE idle states\n",
nr_xcede_records);
payload = &xcede_latency_parameter.payload;
/*
* The CEDE idle state maps to CEDE(0). While the hypervisor
* does not advertise CEDE(0) exit latency values, it does
* advertise the latency values of the extended CEDE states.
* We use the lowest advertised exit latency value as a proxy
* for the exit latency of CEDE(0).
*/
for (i = 0; i < nr_xcede_records; i++) {
struct xcede_latency_record *record = &payload->records[i];
u8 hint = record->hint;
u64 latency_tb = be64_to_cpu(record->latency_ticks);
u64 latency_us = DIV_ROUND_UP_ULL(tb_to_ns(latency_tb), NSEC_PER_USEC);
/*
* We expect the exit latency of an extended CEDE
* state to be non-zero, it to since it takes at least
* a few nanoseconds to wakeup the idle CPU and
* dispatch the virtual processor into the Linux
* Guest.
*
* So we consider only non-zero value for performing
* the fixup of CEDE(0) latency.
*/
if (latency_us == 0) {
pr_warn("cpuidle: Skipping xcede record %d [hint=%d]. Exit latency = 0us\n",
i, hint);
continue;
}
if (latency_us < min_xcede_latency_us)
min_xcede_latency_us = latency_us;
}
if (min_xcede_latency_us != UINT_MAX) {
dedicated_states[1].exit_latency = min_xcede_latency_us;
dedicated_states[1].target_residency = 10 * (min_xcede_latency_us);
pr_info("cpuidle: Fixed up CEDE exit latency to %llu us\n",
min_xcede_latency_us);
}
}
/*
* pseries_idle_probe()
* Choose state table for shared versus dedicated partition
*/
static int __init pseries_idle_probe(void)
{
if (cpuidle_disable != IDLE_NO_OVERRIDE)
return -ENODEV;
if (firmware_has_feature(FW_FEATURE_SPLPAR)) {
if (lppaca_shared_proc()) {
cpuidle_state_table = shared_states;
max_idle_state = ARRAY_SIZE(shared_states);
} else {
/*
* Use firmware provided latency values
* starting with POWER10 platforms. In the
* case that we are running on a POWER10
* platform but in an earlier compat mode, we
* can still use the firmware provided values.
*
* However, on platforms prior to POWER10, we
* cannot rely on the accuracy of the firmware
* provided latency values. On such platforms,
* go with the conservative default estimate
* of 10us.
*/
if (cpu_has_feature(CPU_FTR_ARCH_31) || pvr_version_is(PVR_POWER10))
fixup_cede0_latency();
cpuidle_state_table = dedicated_states;
max_idle_state = NR_DEDICATED_STATES;
}
} else
return -ENODEV;
if (max_idle_state > 1) {
snooze_timeout_en = true;
snooze_timeout = cpuidle_state_table[1].target_residency *
tb_ticks_per_usec;
}
return 0;
}
static int __init pseries_processor_idle_init(void)
{
int retval;
retval = pseries_idle_probe();
if (retval)
return retval;
pseries_cpuidle_driver_init();
retval = cpuidle_register(&pseries_idle_driver, NULL);
if (retval) {
printk(KERN_DEBUG "Registration of pseries driver failed.\n");
return retval;
}
retval = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
"cpuidle/pseries:online",
pseries_cpuidle_cpu_online, NULL);
WARN_ON(retval < 0);
retval = cpuhp_setup_state_nocalls(CPUHP_CPUIDLE_DEAD,
"cpuidle/pseries:DEAD", NULL,
pseries_cpuidle_cpu_dead);
WARN_ON(retval < 0);
printk(KERN_DEBUG "pseries_idle_driver registered\n");
return 0;
}
device_initcall(pseries_processor_idle_init);
Codebase Browser
linux