1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * linux/arch/arm/kernel/smp_twd.c
4 *
5 * Copyright (C) 2002 ARM Ltd.
6 * All Rights Reserved
7 */
8 #include <linux/init.h>
9 #include <linux/kernel.h>
10 #include <linux/clk.h>
11 #include <linux/cpu.h>
12 #include <linux/delay.h>
13 #include <linux/device.h>
14 #include <linux/err.h>
15 #include <linux/smp.h>
16 #include <linux/jiffies.h>
17 #include <linux/clockchips.h>
18 #include <linux/interrupt.h>
19 #include <linux/io.h>
20 #include <linux/of_irq.h>
21 #include <linux/of_address.h>
22
23 #include <asm/smp_twd.h>
24
25 /* set up by the platform code */
26 static void __iomem *twd_base;
27
28 static struct clk *twd_clk;
29 static unsigned long twd_timer_rate;
30 static DEFINE_PER_CPU(bool, percpu_setup_called);
31
32 static struct clock_event_device __percpu *twd_evt;
33 static unsigned int twd_features =
34 CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
35 static int twd_ppi;
36
37 static int twd_shutdown(struct clock_event_device *clk)
38 {
39 writel_relaxed(0, twd_base + TWD_TIMER_CONTROL);
40 return 0;
41 }
42
43 static int twd_set_oneshot(struct clock_event_device *clk)
44 {
45 /* period set, and timer enabled in 'next_event' hook */
46 writel_relaxed(TWD_TIMER_CONTROL_IT_ENABLE | TWD_TIMER_CONTROL_ONESHOT,
47 twd_base + TWD_TIMER_CONTROL);
48 return 0;
49 }
50
51 static int twd_set_periodic(struct clock_event_device *clk)
52 {
53 unsigned long ctrl = TWD_TIMER_CONTROL_ENABLE |
54 TWD_TIMER_CONTROL_IT_ENABLE |
55 TWD_TIMER_CONTROL_PERIODIC;
56
57 writel_relaxed(DIV_ROUND_CLOSEST(twd_timer_rate, HZ),
58 twd_base + TWD_TIMER_LOAD);
59 writel_relaxed(ctrl, twd_base + TWD_TIMER_CONTROL);
60 return 0;
61 }
62
63 static int twd_set_next_event(unsigned long evt,
64 struct clock_event_device *unused)
65 {
66 unsigned long ctrl = readl_relaxed(twd_base + TWD_TIMER_CONTROL);
67
68 ctrl |= TWD_TIMER_CONTROL_ENABLE;
69
70 writel_relaxed(evt, twd_base + TWD_TIMER_COUNTER);
71 writel_relaxed(ctrl, twd_base + TWD_TIMER_CONTROL);
72
73 return 0;
74 }
75
76 /*
77 * local_timer_ack: checks for a local timer interrupt.
78 *
79 * If a local timer interrupt has occurred, acknowledge and return 1.
80 * Otherwise, return 0.
81 */
82 static int twd_timer_ack(void)
83 {
84 if (readl_relaxed(twd_base + TWD_TIMER_INTSTAT)) {
85 writel_relaxed(1, twd_base + TWD_TIMER_INTSTAT);
86 return 1;
87 }
88
89 return 0;
90 }
91
92 static void twd_timer_stop(void)
93 {
94 struct clock_event_device *clk = raw_cpu_ptr(twd_evt);
95
96 twd_shutdown(clk);
97 disable_percpu_irq(clk->irq);
98 }
99
100 /*
101 * Updates clockevent frequency when the cpu frequency changes.
102 * Called on the cpu that is changing frequency with interrupts disabled.
103 */
104 static void twd_update_frequency(void *new_rate)
105 {
106 twd_timer_rate = *((unsigned long *) new_rate);
107
108 clockevents_update_freq(raw_cpu_ptr(twd_evt), twd_timer_rate);
109 }
110
111 static int twd_rate_change(struct notifier_block *nb,
112 unsigned long flags, void *data)
113 {
114 struct clk_notifier_data *cnd = data;
115
116 /*
117 * The twd clock events must be reprogrammed to account for the new
118 * frequency. The timer is local to a cpu, so cross-call to the
119 * changing cpu.
120 */
121 if (flags == POST_RATE_CHANGE)
122 on_each_cpu(twd_update_frequency,
123 (void *)&cnd->new_rate, 1);
124
125 return NOTIFY_OK;
126 }
127
128 static struct notifier_block twd_clk_nb = {
129 .notifier_call = twd_rate_change,
130 };
131
132 static int twd_clk_init(void)
133 {
134 if (twd_evt && raw_cpu_ptr(twd_evt) && !IS_ERR(twd_clk))
135 return clk_notifier_register(twd_clk, &twd_clk_nb);
136
137 return 0;
138 }
139 core_initcall(twd_clk_init);
140
141 static void twd_calibrate_rate(void)
142 {
143 unsigned long count;
144 u64 waitjiffies;
145
146 /*
147 * If this is the first time round, we need to work out how fast
148 * the timer ticks
149 */
150 if (twd_timer_rate == 0) {
151 pr_info("Calibrating local timer... ");
152
153 /* Wait for a tick to start */
154 waitjiffies = get_jiffies_64() + 1;
155
156 while (get_jiffies_64() < waitjiffies)
157 udelay(10);
158
159 /* OK, now the tick has started, let's get the timer going */
160 waitjiffies += 5;
161
162 /* enable, no interrupt or reload */
163 writel_relaxed(0x1, twd_base + TWD_TIMER_CONTROL);
164
165 /* maximum value */
166 writel_relaxed(0xFFFFFFFFU, twd_base + TWD_TIMER_COUNTER);
167
168 while (get_jiffies_64() < waitjiffies)
169 udelay(10);
170
171 count = readl_relaxed(twd_base + TWD_TIMER_COUNTER);
172
173 twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
174
175 pr_cont("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
176 (twd_timer_rate / 10000) % 100);
177 }
178 }
179
180 static irqreturn_t twd_handler(int irq, void *dev_id)
181 {
182 struct clock_event_device *evt = dev_id;
183
184 if (twd_timer_ack()) {
185 evt->event_handler(evt);
186 return IRQ_HANDLED;
187 }
188
189 return IRQ_NONE;
190 }
191
192 static void twd_get_clock(struct device_node *np)
193 {
194 int err;
195
196 if (np)
197 twd_clk = of_clk_get(np, 0);
198 else
199 twd_clk = clk_get_sys("smp_twd", NULL);
200
201 if (IS_ERR(twd_clk)) {
202 pr_err("smp_twd: clock not found %d\n", (int) PTR_ERR(twd_clk));
203 return;
204 }
205
206 err = clk_prepare_enable(twd_clk);
207 if (err) {
208 pr_err("smp_twd: clock failed to prepare+enable: %d\n", err);
209 clk_put(twd_clk);
210 return;
211 }
212
213 twd_timer_rate = clk_get_rate(twd_clk);
214 }
215
216 /*
217 * Setup the local clock events for a CPU.
218 */
219 static void twd_timer_setup(void)
220 {
221 struct clock_event_device *clk = raw_cpu_ptr(twd_evt);
222 int cpu = smp_processor_id();
223
224 /*
225 * If the basic setup for this CPU has been done before don't
226 * bother with the below.
227 */
228 if (per_cpu(percpu_setup_called, cpu)) {
229 writel_relaxed(0, twd_base + TWD_TIMER_CONTROL);
230 clockevents_register_device(clk);
231 enable_percpu_irq(clk->irq, 0);
232 return;
233 }
234 per_cpu(percpu_setup_called, cpu) = true;
235
236 twd_calibrate_rate();
237
238 /*
239 * The following is done once per CPU the first time .setup() is
240 * called.
241 */
242 writel_relaxed(0, twd_base + TWD_TIMER_CONTROL);
243
244 clk->name = "local_timer";
245 clk->features = twd_features;
246 clk->rating = 350;
247 clk->set_state_shutdown = twd_shutdown;
248 clk->set_state_periodic = twd_set_periodic;
249 clk->set_state_oneshot = twd_set_oneshot;
250 clk->tick_resume = twd_shutdown;
251 clk->set_next_event = twd_set_next_event;
252 clk->irq = twd_ppi;
253 clk->cpumask = cpumask_of(cpu);
254
255 clockevents_config_and_register(clk, twd_timer_rate,
256 0xf, 0xffffffff);
257 enable_percpu_irq(clk->irq, 0);
258 }
259
260 static int twd_timer_starting_cpu(unsigned int cpu)
261 {
262 twd_timer_setup();
263 return 0;
264 }
265
266 static int twd_timer_dying_cpu(unsigned int cpu)
267 {
268 twd_timer_stop();
269 return 0;
270 }
271
272 static int __init twd_local_timer_common_register(struct device_node *np)
273 {
274 int err;
275
276 twd_evt = alloc_percpu(struct clock_event_device);
277 if (!twd_evt) {
278 err = -ENOMEM;
279 goto out_free;
280 }
281
282 err = request_percpu_irq(twd_ppi, twd_handler, "twd", twd_evt);
283 if (err) {
284 pr_err("twd: can't register interrupt %d (%d)\n", twd_ppi, err);
285 goto out_free;
286 }
287
288 cpuhp_setup_state_nocalls(CPUHP_AP_ARM_TWD_STARTING,
289 "arm/timer/twd:starting",
290 twd_timer_starting_cpu, twd_timer_dying_cpu);
291
292 twd_get_clock(np);
293 if (!of_property_read_bool(np, "always-on"))
294 twd_features |= CLOCK_EVT_FEAT_C3STOP;
295
296 /*
297 * Immediately configure the timer on the boot CPU, unless we need
298 * jiffies to be incrementing to calibrate the rate in which case
299 * setup the timer in late_time_init.
300 */
301 if (twd_timer_rate)
302 twd_timer_setup();
303 else
304 late_time_init = twd_timer_setup;
305
306 return 0;
307
308 out_free:
309 iounmap(twd_base);
310 twd_base = NULL;
311 free_percpu(twd_evt);
312
313 return err;
314 }
315
316 static int __init twd_local_timer_of_register(struct device_node *np)
317 {
318 int err;
319
320 twd_ppi = irq_of_parse_and_map(np, 0);
321 if (!twd_ppi) {
322 err = -EINVAL;
323 goto out;
324 }
325
326 twd_base = of_iomap(np, 0);
327 if (!twd_base) {
328 err = -ENOMEM;
329 goto out;
330 }
331
332 err = twd_local_timer_common_register(np);
333
334 out:
335 WARN(err, "twd_local_timer_of_register failed (%d)\n", err);
336 return err;
337 }
338 TIMER_OF_DECLARE(arm_twd_a9, "arm,cortex-a9-twd-timer", twd_local_timer_of_register);
339 TIMER_OF_DECLARE(arm_twd_a5, "arm,cortex-a5-twd-timer", twd_local_timer_of_register);
340 TIMER_OF_DECLARE(arm_twd_11mp, "arm,arm11mp-twd-timer", twd_local_timer_of_register);
341
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