// 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 #include #include #include #include #include #include #include #include #include #include #include #include #include #include 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);