1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (C) 2020 Western Digital Corporation or its affiliates.
4  *
5  * Most of the M-mode (i.e. NoMMU) RISC-V systems usually have a
6  * CLINT MMIO timer device.
7  */
8 
9 #define pr_fmt(fmt) "clint: " fmt
10 #include <linux/bitops.h>
11 #include <linux/clocksource.h>
12 #include <linux/clockchips.h>
13 #include <linux/cpu.h>
14 #include <linux/delay.h>
15 #include <linux/module.h>
16 #include <linux/of_address.h>
17 #include <linux/sched_clock.h>
18 #include <linux/io-64-nonatomic-lo-hi.h>
19 #include <linux/interrupt.h>
20 #include <linux/irq.h>
21 #include <linux/irqchip/chained_irq.h>
22 #include <linux/irqdomain.h>
23 #include <linux/of_irq.h>
24 #include <linux/smp.h>
25 #include <linux/timex.h>
26 
27 #ifndef CONFIG_RISCV_M_MODE
28 #include <asm/clint.h>
29 #endif
30 
31 #define CLINT_IPI_OFF		0
32 #define CLINT_TIMER_CMP_OFF	0x4000
33 #define CLINT_TIMER_VAL_OFF	0xbff8
34 
35 /* CLINT manages IPI and Timer for RISC-V M-mode  */
36 static u32 __iomem *clint_ipi_base;
37 static unsigned int clint_ipi_irq;
38 static u64 __iomem *clint_timer_cmp;
39 static u64 __iomem *clint_timer_val;
40 static unsigned long clint_timer_freq;
41 static unsigned int clint_timer_irq;
42 
43 #ifdef CONFIG_RISCV_M_MODE
44 u64 __iomem *clint_time_val;
45 EXPORT_SYMBOL(clint_time_val);
46 #endif
47 
48 #ifdef CONFIG_SMP
clint_send_ipi(unsigned int cpu)49 static void clint_send_ipi(unsigned int cpu)
50 {
51 	writel(1, clint_ipi_base + cpuid_to_hartid_map(cpu));
52 }
53 
clint_clear_ipi(void)54 static void clint_clear_ipi(void)
55 {
56 	writel(0, clint_ipi_base + cpuid_to_hartid_map(smp_processor_id()));
57 }
58 
clint_ipi_interrupt(struct irq_desc * desc)59 static void clint_ipi_interrupt(struct irq_desc *desc)
60 {
61 	struct irq_chip *chip = irq_desc_get_chip(desc);
62 
63 	chained_irq_enter(chip, desc);
64 
65 	clint_clear_ipi();
66 	ipi_mux_process();
67 
68 	chained_irq_exit(chip, desc);
69 }
70 #endif
71 
72 #ifdef CONFIG_64BIT
73 #define clint_get_cycles()	readq_relaxed(clint_timer_val)
74 #else
75 #define clint_get_cycles()	readl_relaxed(clint_timer_val)
76 #define clint_get_cycles_hi()	readl_relaxed(((u32 *)clint_timer_val) + 1)
77 #endif
78 
79 #ifdef CONFIG_64BIT
clint_get_cycles64(void)80 static u64 notrace clint_get_cycles64(void)
81 {
82 	return clint_get_cycles();
83 }
84 #else /* CONFIG_64BIT */
clint_get_cycles64(void)85 static u64 notrace clint_get_cycles64(void)
86 {
87 	u32 hi, lo;
88 
89 	do {
90 		hi = clint_get_cycles_hi();
91 		lo = clint_get_cycles();
92 	} while (hi != clint_get_cycles_hi());
93 
94 	return ((u64)hi << 32) | lo;
95 }
96 #endif /* CONFIG_64BIT */
97 
clint_rdtime(struct clocksource * cs)98 static u64 clint_rdtime(struct clocksource *cs)
99 {
100 	return clint_get_cycles64();
101 }
102 
103 static struct clocksource clint_clocksource = {
104 	.name		= "clint_clocksource",
105 	.rating		= 300,
106 	.mask		= CLOCKSOURCE_MASK(64),
107 	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
108 	.read		= clint_rdtime,
109 };
110 
clint_clock_next_event(unsigned long delta,struct clock_event_device * ce)111 static int clint_clock_next_event(unsigned long delta,
112 				   struct clock_event_device *ce)
113 {
114 	void __iomem *r = clint_timer_cmp +
115 			  cpuid_to_hartid_map(smp_processor_id());
116 
117 	csr_set(CSR_IE, IE_TIE);
118 	writeq_relaxed(clint_get_cycles64() + delta, r);
119 	return 0;
120 }
121 
122 static DEFINE_PER_CPU(struct clock_event_device, clint_clock_event) = {
123 	.name		= "clint_clockevent",
124 	.features	= CLOCK_EVT_FEAT_ONESHOT,
125 	.rating		= 100,
126 	.set_next_event	= clint_clock_next_event,
127 };
128 
clint_timer_starting_cpu(unsigned int cpu)129 static int clint_timer_starting_cpu(unsigned int cpu)
130 {
131 	struct clock_event_device *ce = per_cpu_ptr(&clint_clock_event, cpu);
132 
133 	ce->cpumask = cpumask_of(cpu);
134 	clockevents_config_and_register(ce, clint_timer_freq, 100, 0x7fffffff);
135 
136 	enable_percpu_irq(clint_timer_irq,
137 			  irq_get_trigger_type(clint_timer_irq));
138 	enable_percpu_irq(clint_ipi_irq,
139 			  irq_get_trigger_type(clint_ipi_irq));
140 	return 0;
141 }
142 
clint_timer_dying_cpu(unsigned int cpu)143 static int clint_timer_dying_cpu(unsigned int cpu)
144 {
145 	disable_percpu_irq(clint_timer_irq);
146 	/*
147 	 * Don't disable IPI when CPU goes offline because
148 	 * the masking/unmasking of virtual IPIs is done
149 	 * via generic IPI-Mux
150 	 */
151 	return 0;
152 }
153 
clint_timer_interrupt(int irq,void * dev_id)154 static irqreturn_t clint_timer_interrupt(int irq, void *dev_id)
155 {
156 	struct clock_event_device *evdev = this_cpu_ptr(&clint_clock_event);
157 
158 	csr_clear(CSR_IE, IE_TIE);
159 	evdev->event_handler(evdev);
160 
161 	return IRQ_HANDLED;
162 }
163 
clint_timer_init_dt(struct device_node * np)164 static int __init clint_timer_init_dt(struct device_node *np)
165 {
166 	int rc;
167 	u32 i, nr_irqs;
168 	void __iomem *base;
169 	struct of_phandle_args oirq;
170 
171 	/*
172 	 * Ensure that CLINT device interrupts are either RV_IRQ_TIMER or
173 	 * RV_IRQ_SOFT. If it's anything else then we ignore the device.
174 	 */
175 	nr_irqs = of_irq_count(np);
176 	for (i = 0; i < nr_irqs; i++) {
177 		if (of_irq_parse_one(np, i, &oirq)) {
178 			pr_err("%pOFP: failed to parse irq %d.\n", np, i);
179 			continue;
180 		}
181 
182 		if ((oirq.args_count != 1) ||
183 		    (oirq.args[0] != RV_IRQ_TIMER &&
184 		     oirq.args[0] != RV_IRQ_SOFT)) {
185 			pr_err("%pOFP: invalid irq %d (hwirq %d)\n",
186 			       np, i, oirq.args[0]);
187 			return -ENODEV;
188 		}
189 
190 		/* Find parent irq domain and map ipi irq */
191 		if (!clint_ipi_irq &&
192 		    oirq.args[0] == RV_IRQ_SOFT &&
193 		    irq_find_host(oirq.np))
194 			clint_ipi_irq = irq_of_parse_and_map(np, i);
195 
196 		/* Find parent irq domain and map timer irq */
197 		if (!clint_timer_irq &&
198 		    oirq.args[0] == RV_IRQ_TIMER &&
199 		    irq_find_host(oirq.np))
200 			clint_timer_irq = irq_of_parse_and_map(np, i);
201 	}
202 
203 	/* If CLINT ipi or timer irq not found then fail */
204 	if (!clint_ipi_irq || !clint_timer_irq) {
205 		pr_err("%pOFP: ipi/timer irq not found\n", np);
206 		return -ENODEV;
207 	}
208 
209 	base = of_iomap(np, 0);
210 	if (!base) {
211 		pr_err("%pOFP: could not map registers\n", np);
212 		return -ENODEV;
213 	}
214 
215 	clint_ipi_base = base + CLINT_IPI_OFF;
216 	clint_timer_cmp = base + CLINT_TIMER_CMP_OFF;
217 	clint_timer_val = base + CLINT_TIMER_VAL_OFF;
218 	clint_timer_freq = riscv_timebase;
219 
220 #ifdef CONFIG_RISCV_M_MODE
221 	/*
222 	 * Yes, that's an odd naming scheme.  time_val is public, but hopefully
223 	 * will die in favor of something cleaner.
224 	 */
225 	clint_time_val = clint_timer_val;
226 #endif
227 
228 	pr_info("%pOFP: timer running at %ld Hz\n", np, clint_timer_freq);
229 
230 	rc = clocksource_register_hz(&clint_clocksource, clint_timer_freq);
231 	if (rc) {
232 		pr_err("%pOFP: clocksource register failed [%d]\n", np, rc);
233 		goto fail_iounmap;
234 	}
235 
236 	sched_clock_register(clint_get_cycles64, 64, clint_timer_freq);
237 
238 	rc = request_percpu_irq(clint_timer_irq, clint_timer_interrupt,
239 				 "clint-timer", &clint_clock_event);
240 	if (rc) {
241 		pr_err("registering percpu irq failed [%d]\n", rc);
242 		goto fail_iounmap;
243 	}
244 
245 #ifdef CONFIG_SMP
246 	rc = ipi_mux_create(BITS_PER_BYTE, clint_send_ipi);
247 	if (rc <= 0) {
248 		pr_err("unable to create muxed IPIs\n");
249 		rc = (rc < 0) ? rc : -ENODEV;
250 		goto fail_free_irq;
251 	}
252 
253 	irq_set_chained_handler(clint_ipi_irq, clint_ipi_interrupt);
254 	riscv_ipi_set_virq_range(rc, BITS_PER_BYTE, true);
255 	clint_clear_ipi();
256 #endif
257 
258 	rc = cpuhp_setup_state(CPUHP_AP_CLINT_TIMER_STARTING,
259 				"clockevents/clint/timer:starting",
260 				clint_timer_starting_cpu,
261 				clint_timer_dying_cpu);
262 	if (rc) {
263 		pr_err("%pOFP: cpuhp setup state failed [%d]\n", np, rc);
264 		goto fail_free_irq;
265 	}
266 
267 	return 0;
268 
269 fail_free_irq:
270 	free_percpu_irq(clint_timer_irq, &clint_clock_event);
271 fail_iounmap:
272 	iounmap(base);
273 	return rc;
274 }
275 
276 TIMER_OF_DECLARE(clint_timer, "riscv,clint0", clint_timer_init_dt);
277 TIMER_OF_DECLARE(clint_timer1, "sifive,clint0", clint_timer_init_dt);
278