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// SPDX-License-Identifier: GPL-2.0
* Copyright (C) 2012 Regents of the University of California
* Copyright (C) 2017 SiFive
* All RISC-V systems have a timer attached to every hart. These timers can
* either be read from the "time" and "timeh" CSRs, and can use the SBI to
* setup events, or directly accessed using MMIO registers.
#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <linux/cpu.h>
#include <linux/delay.h>
#include <linux/irq.h>
#include <linux/irqdomain.h>
#include <linux/sched_clock.h>
#include <linux/io-64-nonatomic-lo-hi.h>
#include <linux/interrupt.h>
#include <linux/of_irq.h>
#include <asm/smp.h>
#include <asm/sbi.h>
#include <asm/timex.h>
static int riscv_clock_next_event(unsigned long delta,
struct clock_event_device *ce)
csr_set(CSR_IE, IE_TIE);
sbi_set_timer(get_cycles64() + delta);
return 0;
static unsigned int riscv_clock_event_irq;
static DEFINE_PER_CPU(struct clock_event_device, riscv_clock_event) = {
.name = "riscv_timer_clockevent",
.rating = 100,
.set_next_event = riscv_clock_next_event,
* It is guaranteed that all the timers across all the harts are synchronized
* within one tick of each other, so while this could technically go
* backwards when hopping between CPUs, practically it won't happen.
static unsigned long long riscv_clocksource_rdtime(struct clocksource *cs)
return get_cycles64();
static u64 notrace riscv_sched_clock(void)
return get_cycles64();
static struct clocksource riscv_clocksource = {
.name = "riscv_clocksource",
.rating = 300,
.read = riscv_clocksource_rdtime,
static int riscv_timer_starting_cpu(unsigned int cpu)
struct clock_event_device *ce = per_cpu_ptr(&riscv_clock_event, cpu);
ce->cpumask = cpumask_of(cpu);
ce->irq = riscv_clock_event_irq;
clockevents_config_and_register(ce, riscv_timebase, 100, 0x7fffffff);
return 0;
static int riscv_timer_dying_cpu(unsigned int cpu)
return 0;
/* called directly from the low-level interrupt handler */
static irqreturn_t riscv_timer_interrupt(int irq, void *dev_id)
struct clock_event_device *evdev = this_cpu_ptr(&riscv_clock_event);
csr_clear(CSR_IE, IE_TIE);
static int __init riscv_timer_init_dt(struct device_node *n)
int cpuid, hartid, error;
struct device_node *child;
struct irq_domain *domain;
hartid = riscv_of_processor_hartid(n);
if (hartid < 0) {
pr_warn("Not valid hartid for node [%pOF] error = [%d]\n",
n, hartid);
return hartid;
cpuid = riscv_hartid_to_cpuid(hartid);
if (cpuid < 0) {
pr_warn("Invalid cpuid for hartid [%d]\n", hartid);
return cpuid;
if (cpuid != smp_processor_id())
return 0;
domain = NULL;
child = of_get_compatible_child(n, "riscv,cpu-intc");
if (!child) {
pr_err("Failed to find INTC node [%pOF]\n", n);
return -ENODEV;
domain = irq_find_host(child);
if (!domain) {
pr_err("Failed to find IRQ domain for node [%pOF]\n", n);
return -ENODEV;
riscv_clock_event_irq = irq_create_mapping(domain, RV_IRQ_TIMER);
if (!riscv_clock_event_irq) {
pr_err("Failed to map timer interrupt for node [%pOF]\n", n);
return -ENODEV;
pr_info("%s: Registering clocksource cpuid [%d] hartid [%d]\n",
__func__, cpuid, hartid);
error = clocksource_register_hz(&riscv_clocksource, riscv_timebase);
if (error) {
pr_err("RISCV timer register failed [%d] for cpu = [%d]\n",
error, cpuid);
return error;
sched_clock_register(riscv_sched_clock, 64, riscv_timebase);
error = request_percpu_irq(riscv_clock_event_irq,
"riscv-timer", &riscv_clock_event);
if (error) {
pr_err("registering percpu irq failed [%d]\n", error);
return error;
error = cpuhp_setup_state(CPUHP_AP_RISCV_TIMER_STARTING,
riscv_timer_starting_cpu, riscv_timer_dying_cpu);
if (error)
pr_err("cpu hp setup state failed for RISCV timer [%d]\n",
return error;
TIMER_OF_DECLARE(riscv_timer, "riscv", riscv_timer_init_dt);