summaryrefslogtreecommitdiffstats
path: root/drivers/cpuidle/cpuidle-pseries.c
diff options
context:
space:
mode:
Diffstat (limited to 'drivers/cpuidle/cpuidle-pseries.c')
-rw-r--r--drivers/cpuidle/cpuidle-pseries.c473
1 files changed, 473 insertions, 0 deletions
diff --git a/drivers/cpuidle/cpuidle-pseries.c b/drivers/cpuidle/cpuidle-pseries.c
new file mode 100644
index 000000000..0590001db
--- /dev/null
+++ b/drivers/cpuidle/cpuidle-pseries.c
@@ -0,0 +1,473 @@
+// 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 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();
+ local_irq_enable();
+ snooze_exit_time = get_tb() + snooze_timeout;
+
+ 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().
+ */
+ clear_thread_flag(TIF_POLLING_NRFLAG);
+ smp_mb();
+ break;
+ }
+ }
+
+ HMT_medium();
+ clear_thread_flag(TIF_POLLING_NRFLAG);
+
+ local_irq_disable();
+
+ pseries_idle_epilog();
+
+ return index;
+}
+
+static 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 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();
+
+ local_irq_disable();
+ get_lppaca()->donate_dedicated_cpu = 0;
+ get_lppaca()->cede_latency_hint = old_latency_hint;
+
+ pseries_idle_epilog();
+
+ return index;
+}
+
+static 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();
+
+ 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 },
+ { /* 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 },
+ { /* 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);
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-04 18:40:49 +0000