1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (C) 2012 Regents of the University of California 4 * Copyright (C) 2017 SiFive 5 * 6 * All RISC-V systems have a timer attached to every hart. These timers can 7 * either be read from the "time" and "timeh" CSRs, and can use the SBI to 8 * setup events, or directly accessed using MMIO registers. 9 */ 10 #include <linux/clocksource.h> 11 #include <linux/clockchips.h> 12 #include <linux/cpu.h> 13 #include <linux/delay.h> 14 #include <linux/irq.h> 15 #include <linux/sched_clock.h> 16 #include <linux/io-64-nonatomic-lo-hi.h> 17 #include <asm/smp.h> 18 #include <asm/sbi.h> 19 20 u64 __iomem *riscv_time_cmp; 21 u64 __iomem *riscv_time_val; 22 23 static inline void mmio_set_timer(u64 val) 24 { 25 void __iomem *r; 26 27 r = riscv_time_cmp + cpuid_to_hartid_map(smp_processor_id()); 28 writeq_relaxed(val, r); 29 } 30 31 static int riscv_clock_next_event(unsigned long delta, 32 struct clock_event_device *ce) 33 { 34 csr_set(CSR_IE, IE_TIE); 35 if (IS_ENABLED(CONFIG_RISCV_SBI)) 36 sbi_set_timer(get_cycles64() + delta); 37 else 38 mmio_set_timer(get_cycles64() + delta); 39 return 0; 40 } 41 42 static DEFINE_PER_CPU(struct clock_event_device, riscv_clock_event) = { 43 .name = "riscv_timer_clockevent", 44 .features = CLOCK_EVT_FEAT_ONESHOT, 45 .rating = 100, 46 .set_next_event = riscv_clock_next_event, 47 }; 48 49 /* 50 * It is guaranteed that all the timers across all the harts are synchronized 51 * within one tick of each other, so while this could technically go 52 * backwards when hopping between CPUs, practically it won't happen. 53 */ 54 static unsigned long long riscv_clocksource_rdtime(struct clocksource *cs) 55 { 56 return get_cycles64(); 57 } 58 59 static u64 notrace riscv_sched_clock(void) 60 { 61 return get_cycles64(); 62 } 63 64 static struct clocksource riscv_clocksource = { 65 .name = "riscv_clocksource", 66 .rating = 300, 67 .mask = CLOCKSOURCE_MASK(64), 68 .flags = CLOCK_SOURCE_IS_CONTINUOUS, 69 .read = riscv_clocksource_rdtime, 70 }; 71 72 static int riscv_timer_starting_cpu(unsigned int cpu) 73 { 74 struct clock_event_device *ce = per_cpu_ptr(&riscv_clock_event, cpu); 75 76 ce->cpumask = cpumask_of(cpu); 77 clockevents_config_and_register(ce, riscv_timebase, 100, 0x7fffffff); 78 79 csr_set(CSR_IE, IE_TIE); 80 return 0; 81 } 82 83 static int riscv_timer_dying_cpu(unsigned int cpu) 84 { 85 csr_clear(CSR_IE, IE_TIE); 86 return 0; 87 } 88 89 /* called directly from the low-level interrupt handler */ 90 void riscv_timer_interrupt(void) 91 { 92 struct clock_event_device *evdev = this_cpu_ptr(&riscv_clock_event); 93 94 csr_clear(CSR_IE, IE_TIE); 95 evdev->event_handler(evdev); 96 } 97 98 static int __init riscv_timer_init_dt(struct device_node *n) 99 { 100 int cpuid, hartid, error; 101 102 hartid = riscv_of_processor_hartid(n); 103 if (hartid < 0) { 104 pr_warn("Not valid hartid for node [%pOF] error = [%d]\n", 105 n, hartid); 106 return hartid; 107 } 108 109 cpuid = riscv_hartid_to_cpuid(hartid); 110 if (cpuid < 0) { 111 pr_warn("Invalid cpuid for hartid [%d]\n", hartid); 112 return cpuid; 113 } 114 115 if (cpuid != smp_processor_id()) 116 return 0; 117 118 pr_info("%s: Registering clocksource cpuid [%d] hartid [%d]\n", 119 __func__, cpuid, hartid); 120 error = clocksource_register_hz(&riscv_clocksource, riscv_timebase); 121 if (error) { 122 pr_err("RISCV timer register failed [%d] for cpu = [%d]\n", 123 error, cpuid); 124 return error; 125 } 126 127 sched_clock_register(riscv_sched_clock, 64, riscv_timebase); 128 129 error = cpuhp_setup_state(CPUHP_AP_RISCV_TIMER_STARTING, 130 "clockevents/riscv/timer:starting", 131 riscv_timer_starting_cpu, riscv_timer_dying_cpu); 132 if (error) 133 pr_err("cpu hp setup state failed for RISCV timer [%d]\n", 134 error); 135 return error; 136 } 137 138 TIMER_OF_DECLARE(riscv_timer, "riscv", riscv_timer_init_dt); 139