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/irqdomain.h>
 16#include <linux/sched_clock.h>
 17#include <linux/io-64-nonatomic-lo-hi.h>
 18#include <linux/interrupt.h>
 19#include <linux/of_irq.h>
 20#include <asm/smp.h>
 21#include <asm/sbi.h>
 22#include <asm/timex.h>
 23
 24static int riscv_clock_next_event(unsigned long delta,
 25		struct clock_event_device *ce)
 26{
 27	csr_set(CSR_IE, IE_TIE);
 28	sbi_set_timer(get_cycles64() + delta);
 29	return 0;
 30}
 31
 32static unsigned int riscv_clock_event_irq;
 33static DEFINE_PER_CPU(struct clock_event_device, riscv_clock_event) = {
 34	.name			= "riscv_timer_clockevent",
 35	.features		= CLOCK_EVT_FEAT_ONESHOT,
 36	.rating			= 100,
 37	.set_next_event		= riscv_clock_next_event,
 38};
 39
 40/*
 41 * It is guaranteed that all the timers across all the harts are synchronized
 42 * within one tick of each other, so while this could technically go
 43 * backwards when hopping between CPUs, practically it won't happen.
 44 */
 45static unsigned long long riscv_clocksource_rdtime(struct clocksource *cs)
 46{
 47	return get_cycles64();
 48}
 49
 50static u64 notrace riscv_sched_clock(void)
 51{
 52	return get_cycles64();
 53}
 54
 55static struct clocksource riscv_clocksource = {
 56	.name		= "riscv_clocksource",
 57	.rating		= 300,
 58	.mask		= CLOCKSOURCE_MASK(64),
 59	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
 60	.read		= riscv_clocksource_rdtime,
 61};
 62
 63static int riscv_timer_starting_cpu(unsigned int cpu)
 64{
 65	struct clock_event_device *ce = per_cpu_ptr(&riscv_clock_event, cpu);
 66
 67	ce->cpumask = cpumask_of(cpu);
 68	ce->irq = riscv_clock_event_irq;
 69	clockevents_config_and_register(ce, riscv_timebase, 100, 0x7fffffff);
 70
 71	enable_percpu_irq(riscv_clock_event_irq,
 72			  irq_get_trigger_type(riscv_clock_event_irq));
 73	return 0;
 74}
 75
 76static int riscv_timer_dying_cpu(unsigned int cpu)
 77{
 78	disable_percpu_irq(riscv_clock_event_irq);
 79	return 0;
 80}
 81
 82/* called directly from the low-level interrupt handler */
 83static irqreturn_t riscv_timer_interrupt(int irq, void *dev_id)
 84{
 85	struct clock_event_device *evdev = this_cpu_ptr(&riscv_clock_event);
 86
 87	csr_clear(CSR_IE, IE_TIE);
 88	evdev->event_handler(evdev);
 89
 90	return IRQ_HANDLED;
 91}
 92
 93static int __init riscv_timer_init_dt(struct device_node *n)
 94{
 95	int cpuid, hartid, error;
 96	struct device_node *child;
 97	struct irq_domain *domain;
 98
 99	hartid = riscv_of_processor_hartid(n);
100	if (hartid < 0) {
101		pr_warn("Not valid hartid for node [%pOF] error = [%d]\n",
102			n, hartid);
103		return hartid;
104	}
105
106	cpuid = riscv_hartid_to_cpuid(hartid);
107	if (cpuid < 0) {
108		pr_warn("Invalid cpuid for hartid [%d]\n", hartid);
109		return cpuid;
110	}
111
112	if (cpuid != smp_processor_id())
113		return 0;
114
115	domain = NULL;
116	child = of_get_compatible_child(n, "riscv,cpu-intc");
117	if (!child) {
118		pr_err("Failed to find INTC node [%pOF]\n", n);
119		return -ENODEV;
120	}
121	domain = irq_find_host(child);
122	of_node_put(child);
123	if (!domain) {
124		pr_err("Failed to find IRQ domain for node [%pOF]\n", n);
125		return -ENODEV;
126	}
127
128	riscv_clock_event_irq = irq_create_mapping(domain, RV_IRQ_TIMER);
129	if (!riscv_clock_event_irq) {
130		pr_err("Failed to map timer interrupt for node [%pOF]\n", n);
131		return -ENODEV;
132	}
133
134	pr_info("%s: Registering clocksource cpuid [%d] hartid [%d]\n",
135	       __func__, cpuid, hartid);
136	error = clocksource_register_hz(&riscv_clocksource, riscv_timebase);
137	if (error) {
138		pr_err("RISCV timer register failed [%d] for cpu = [%d]\n",
139		       error, cpuid);
140		return error;
141	}
142
143	sched_clock_register(riscv_sched_clock, 64, riscv_timebase);
144
145	error = request_percpu_irq(riscv_clock_event_irq,
146				    riscv_timer_interrupt,
147				    "riscv-timer", &riscv_clock_event);
148	if (error) {
149		pr_err("registering percpu irq failed [%d]\n", error);
150		return error;
151	}
152
153	error = cpuhp_setup_state(CPUHP_AP_RISCV_TIMER_STARTING,
154			 "clockevents/riscv/timer:starting",
155			 riscv_timer_starting_cpu, riscv_timer_dying_cpu);
156	if (error)
157		pr_err("cpu hp setup state failed for RISCV timer [%d]\n",
158		       error);
159	return error;
160}
161
162TIMER_OF_DECLARE(riscv_timer, "riscv", riscv_timer_init_dt);