tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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
11#define pr_fmt(fmt) "riscv-timer: " fmt
12
13#include <linux/clocksource.h>
14#include <linux/clockchips.h>
15#include <linux/cpu.h>
16#include <linux/delay.h>
17#include <linux/irq.h>
18#include <linux/irqdomain.h>
19#include <linux/module.h>
20#include <linux/sched_clock.h>
21#include <linux/io-64-nonatomic-lo-hi.h>
22#include <linux/interrupt.h>
23#include <linux/of_irq.h>
24#include <clocksource/timer-riscv.h>
25#include <asm/smp.h>
26#include <asm/hwcap.h>
27#include <asm/sbi.h>
28#include <asm/timex.h>
29
30static DEFINE_STATIC_KEY_FALSE(riscv_sstc_available);
31
32static int riscv_clock_next_event(unsigned long delta,
33 struct clock_event_device *ce)
34{
35 u64 next_tval = get_cycles64() + delta;
36
37 csr_set(CSR_IE, IE_TIE);
38 if (static_branch_likely(&riscv_sstc_available)) {
39#if defined(CONFIG_32BIT)
40 csr_write(CSR_STIMECMP, next_tval & 0xFFFFFFFF);
41 csr_write(CSR_STIMECMPH, next_tval >> 32);
42#else
43 csr_write(CSR_STIMECMP, next_tval);
44#endif
45 } else
46 sbi_set_timer(next_tval);
47
48 return 0;
49}
50
51static unsigned int riscv_clock_event_irq;
52static DEFINE_PER_CPU(struct clock_event_device, riscv_clock_event) = {
53 .name = "riscv_timer_clockevent",
54 .features = CLOCK_EVT_FEAT_ONESHOT,
55 .rating = 100,
56 .set_next_event = riscv_clock_next_event,
57};
58
59/*
60 * It is guaranteed that all the timers across all the harts are synchronized
61 * within one tick of each other, so while this could technically go
62 * backwards when hopping between CPUs, practically it won't happen.
63 */
64static unsigned long long riscv_clocksource_rdtime(struct clocksource *cs)
65{
66 return get_cycles64();
67}
68
69static u64 notrace riscv_sched_clock(void)
70{
71 return get_cycles64();
72}
73
74static struct clocksource riscv_clocksource = {
75 .name = "riscv_clocksource",
76 .rating = 300,
77 .mask = CLOCKSOURCE_MASK(64),
78 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
79 .read = riscv_clocksource_rdtime,
80};
81
82static int riscv_timer_starting_cpu(unsigned int cpu)
83{
84 struct clock_event_device *ce = per_cpu_ptr(&riscv_clock_event, cpu);
85
86 ce->cpumask = cpumask_of(cpu);
87 ce->irq = riscv_clock_event_irq;
88 clockevents_config_and_register(ce, riscv_timebase, 100, 0x7fffffff);
89
90 enable_percpu_irq(riscv_clock_event_irq,
91 irq_get_trigger_type(riscv_clock_event_irq));
92 return 0;
93}
94
95static int riscv_timer_dying_cpu(unsigned int cpu)
96{
97 disable_percpu_irq(riscv_clock_event_irq);
98 return 0;
99}
100
101void riscv_cs_get_mult_shift(u32 *mult, u32 *shift)
102{
103 *mult = riscv_clocksource.mult;
104 *shift = riscv_clocksource.shift;
105}
106EXPORT_SYMBOL_GPL(riscv_cs_get_mult_shift);
107
108/* called directly from the low-level interrupt handler */
109static irqreturn_t riscv_timer_interrupt(int irq, void *dev_id)
110{
111 struct clock_event_device *evdev = this_cpu_ptr(&riscv_clock_event);
112
113 csr_clear(CSR_IE, IE_TIE);
114 evdev->event_handler(evdev);
115
116 return IRQ_HANDLED;
117}
118
119static int __init riscv_timer_init_dt(struct device_node *n)
120{
121 int cpuid, error;
122 unsigned long hartid;
123 struct device_node *child;
124 struct irq_domain *domain;
125
126 error = riscv_of_processor_hartid(n, &hartid);
127 if (error < 0) {
128 pr_warn("Not valid hartid for node [%pOF] error = [%lu]\n",
129 n, hartid);
130 return error;
131 }
132
133 cpuid = riscv_hartid_to_cpuid(hartid);
134 if (cpuid < 0) {
135 pr_warn("Invalid cpuid for hartid [%lu]\n", hartid);
136 return cpuid;
137 }
138
139 if (cpuid != smp_processor_id())
140 return 0;
141
142 domain = NULL;
143 child = of_get_compatible_child(n, "riscv,cpu-intc");
144 if (!child) {
145 pr_err("Failed to find INTC node [%pOF]\n", n);
146 return -ENODEV;
147 }
148 domain = irq_find_host(child);
149 of_node_put(child);
150 if (!domain) {
151 pr_err("Failed to find IRQ domain for node [%pOF]\n", n);
152 return -ENODEV;
153 }
154
155 riscv_clock_event_irq = irq_create_mapping(domain, RV_IRQ_TIMER);
156 if (!riscv_clock_event_irq) {
157 pr_err("Failed to map timer interrupt for node [%pOF]\n", n);
158 return -ENODEV;
159 }
160
161 pr_info("%s: Registering clocksource cpuid [%d] hartid [%lu]\n",
162 __func__, cpuid, hartid);
163 error = clocksource_register_hz(&riscv_clocksource, riscv_timebase);
164 if (error) {
165 pr_err("RISCV timer register failed [%d] for cpu = [%d]\n",
166 error, cpuid);
167 return error;
168 }
169
170 sched_clock_register(riscv_sched_clock, 64, riscv_timebase);
171
172 error = request_percpu_irq(riscv_clock_event_irq,
173 riscv_timer_interrupt,
174 "riscv-timer", &riscv_clock_event);
175 if (error) {
176 pr_err("registering percpu irq failed [%d]\n", error);
177 return error;
178 }
179
180 error = cpuhp_setup_state(CPUHP_AP_RISCV_TIMER_STARTING,
181 "clockevents/riscv/timer:starting",
182 riscv_timer_starting_cpu, riscv_timer_dying_cpu);
183 if (error)
184 pr_err("cpu hp setup state failed for RISCV timer [%d]\n",
185 error);
186
187 if (riscv_isa_extension_available(NULL, SSTC)) {
188 pr_info("Timer interrupt in S-mode is available via sstc extension\n");
189 static_branch_enable(&riscv_sstc_available);
190 }
191
192 return error;
193}
194
195TIMER_OF_DECLARE(riscv_timer, "riscv", riscv_timer_init_dt);