1 /*
2 * drivers/clocksource/arm_global_timer.c
3 *
4 * Copyright (C) 2013 STMicroelectronics (R&D) Limited.
5 * Author: Stuart Menefy <stuart.menefy@st.com>
6 * Author: Srinivas Kandagatla <srinivas.kandagatla@st.com>
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
11 */
12
13 #include <linux/init.h>
14 #include <linux/interrupt.h>
15 #include <linux/clocksource.h>
16 #include <linux/clockchips.h>
17 #include <linux/cpu.h>
18 #include <linux/clk.h>
19 #include <linux/err.h>
20 #include <linux/io.h>
21 #include <linux/of.h>
22 #include <linux/of_irq.h>
23 #include <linux/of_address.h>
24 #include <linux/sched_clock.h>
25
26 #include <asm/cputype.h>
27
28 #define GT_COUNTER0 0x00
29 #define GT_COUNTER1 0x04
30
31 #define GT_CONTROL 0x08
32 #define GT_CONTROL_TIMER_ENABLE BIT(0) /* this bit is NOT banked */
33 #define GT_CONTROL_COMP_ENABLE BIT(1) /* banked */
34 #define GT_CONTROL_IRQ_ENABLE BIT(2) /* banked */
35 #define GT_CONTROL_AUTO_INC BIT(3) /* banked */
36
37 #define GT_INT_STATUS 0x0c
38 #define GT_INT_STATUS_EVENT_FLAG BIT(0)
39
40 #define GT_COMP0 0x10
41 #define GT_COMP1 0x14
42 #define GT_AUTO_INC 0x18
43
44 /*
45 * We are expecting to be clocked by the ARM peripheral clock.
46 *
47 * Note: it is assumed we are using a prescaler value of zero, so this is
48 * the units for all operations.
49 */
50 static void __iomem *gt_base;
51 static unsigned long gt_clk_rate;
52 static int gt_ppi;
53 static struct clock_event_device __percpu *gt_evt;
54
55 /*
56 * To get the value from the Global Timer Counter register proceed as follows:
57 * 1. Read the upper 32-bit timer counter register
58 * 2. Read the lower 32-bit timer counter register
59 * 3. Read the upper 32-bit timer counter register again. If the value is
60 * different to the 32-bit upper value read previously, go back to step 2.
61 * Otherwise the 64-bit timer counter value is correct.
62 */
_gt_counter_read(void)63 static u64 notrace _gt_counter_read(void)
64 {
65 u64 counter;
66 u32 lower;
67 u32 upper, old_upper;
68
69 upper = readl_relaxed(gt_base + GT_COUNTER1);
70 do {
71 old_upper = upper;
72 lower = readl_relaxed(gt_base + GT_COUNTER0);
73 upper = readl_relaxed(gt_base + GT_COUNTER1);
74 } while (upper != old_upper);
75
76 counter = upper;
77 counter <<= 32;
78 counter |= lower;
79 return counter;
80 }
81
gt_counter_read(void)82 static u64 gt_counter_read(void)
83 {
84 return _gt_counter_read();
85 }
86
87 /**
88 * To ensure that updates to comparator value register do not set the
89 * Interrupt Status Register proceed as follows:
90 * 1. Clear the Comp Enable bit in the Timer Control Register.
91 * 2. Write the lower 32-bit Comparator Value Register.
92 * 3. Write the upper 32-bit Comparator Value Register.
93 * 4. Set the Comp Enable bit and, if necessary, the IRQ enable bit.
94 */
gt_compare_set(unsigned long delta,int periodic)95 static void gt_compare_set(unsigned long delta, int periodic)
96 {
97 u64 counter = gt_counter_read();
98 unsigned long ctrl;
99
100 counter += delta;
101 ctrl = GT_CONTROL_TIMER_ENABLE;
102 writel(ctrl, gt_base + GT_CONTROL);
103 writel(lower_32_bits(counter), gt_base + GT_COMP0);
104 writel(upper_32_bits(counter), gt_base + GT_COMP1);
105
106 if (periodic) {
107 writel(delta, gt_base + GT_AUTO_INC);
108 ctrl |= GT_CONTROL_AUTO_INC;
109 }
110
111 ctrl |= GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE;
112 writel(ctrl, gt_base + GT_CONTROL);
113 }
114
gt_clockevent_shutdown(struct clock_event_device * evt)115 static int gt_clockevent_shutdown(struct clock_event_device *evt)
116 {
117 unsigned long ctrl;
118
119 ctrl = readl(gt_base + GT_CONTROL);
120 ctrl &= ~(GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE |
121 GT_CONTROL_AUTO_INC);
122 writel(ctrl, gt_base + GT_CONTROL);
123 return 0;
124 }
125
gt_clockevent_set_periodic(struct clock_event_device * evt)126 static int gt_clockevent_set_periodic(struct clock_event_device *evt)
127 {
128 gt_compare_set(DIV_ROUND_CLOSEST(gt_clk_rate, HZ), 1);
129 return 0;
130 }
131
gt_clockevent_set_next_event(unsigned long evt,struct clock_event_device * unused)132 static int gt_clockevent_set_next_event(unsigned long evt,
133 struct clock_event_device *unused)
134 {
135 gt_compare_set(evt, 0);
136 return 0;
137 }
138
gt_clockevent_interrupt(int irq,void * dev_id)139 static irqreturn_t gt_clockevent_interrupt(int irq, void *dev_id)
140 {
141 struct clock_event_device *evt = dev_id;
142
143 if (!(readl_relaxed(gt_base + GT_INT_STATUS) &
144 GT_INT_STATUS_EVENT_FLAG))
145 return IRQ_NONE;
146
147 /**
148 * ERRATA 740657( Global Timer can send 2 interrupts for
149 * the same event in single-shot mode)
150 * Workaround:
151 * Either disable single-shot mode.
152 * Or
153 * Modify the Interrupt Handler to avoid the
154 * offending sequence. This is achieved by clearing
155 * the Global Timer flag _after_ having incremented
156 * the Comparator register value to a higher value.
157 */
158 if (clockevent_state_oneshot(evt))
159 gt_compare_set(ULONG_MAX, 0);
160
161 writel_relaxed(GT_INT_STATUS_EVENT_FLAG, gt_base + GT_INT_STATUS);
162 evt->event_handler(evt);
163
164 return IRQ_HANDLED;
165 }
166
gt_clockevents_init(struct clock_event_device * clk)167 static int gt_clockevents_init(struct clock_event_device *clk)
168 {
169 int cpu = smp_processor_id();
170
171 clk->name = "arm_global_timer";
172 clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
173 CLOCK_EVT_FEAT_PERCPU;
174 clk->set_state_shutdown = gt_clockevent_shutdown;
175 clk->set_state_periodic = gt_clockevent_set_periodic;
176 clk->set_state_oneshot = gt_clockevent_shutdown;
177 clk->set_next_event = gt_clockevent_set_next_event;
178 clk->cpumask = cpumask_of(cpu);
179 clk->rating = 300;
180 clk->irq = gt_ppi;
181 clockevents_config_and_register(clk, gt_clk_rate,
182 1, 0xffffffff);
183 enable_percpu_irq(clk->irq, IRQ_TYPE_NONE);
184 return 0;
185 }
186
gt_clockevents_stop(struct clock_event_device * clk)187 static void gt_clockevents_stop(struct clock_event_device *clk)
188 {
189 gt_clockevent_shutdown(clk);
190 disable_percpu_irq(clk->irq);
191 }
192
gt_clocksource_read(struct clocksource * cs)193 static cycle_t gt_clocksource_read(struct clocksource *cs)
194 {
195 return gt_counter_read();
196 }
197
198 static struct clocksource gt_clocksource = {
199 .name = "arm_global_timer",
200 .rating = 300,
201 .read = gt_clocksource_read,
202 .mask = CLOCKSOURCE_MASK(64),
203 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
204 };
205
206 #ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
gt_sched_clock_read(void)207 static u64 notrace gt_sched_clock_read(void)
208 {
209 return _gt_counter_read();
210 }
211 #endif
212
gt_clocksource_init(void)213 static void __init gt_clocksource_init(void)
214 {
215 writel(0, gt_base + GT_CONTROL);
216 writel(0, gt_base + GT_COUNTER0);
217 writel(0, gt_base + GT_COUNTER1);
218 /* enables timer on all the cores */
219 writel(GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL);
220
221 #ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
222 sched_clock_register(gt_sched_clock_read, 64, gt_clk_rate);
223 #endif
224 clocksource_register_hz(>_clocksource, gt_clk_rate);
225 }
226
gt_cpu_notify(struct notifier_block * self,unsigned long action,void * hcpu)227 static int gt_cpu_notify(struct notifier_block *self, unsigned long action,
228 void *hcpu)
229 {
230 switch (action & ~CPU_TASKS_FROZEN) {
231 case CPU_STARTING:
232 gt_clockevents_init(this_cpu_ptr(gt_evt));
233 break;
234 case CPU_DYING:
235 gt_clockevents_stop(this_cpu_ptr(gt_evt));
236 break;
237 }
238
239 return NOTIFY_OK;
240 }
241 static struct notifier_block gt_cpu_nb = {
242 .notifier_call = gt_cpu_notify,
243 };
244
global_timer_of_register(struct device_node * np)245 static void __init global_timer_of_register(struct device_node *np)
246 {
247 struct clk *gt_clk;
248 int err = 0;
249
250 /*
251 * In A9 r2p0 the comparators for each processor with the global timer
252 * fire when the timer value is greater than or equal to. In previous
253 * revisions the comparators fired when the timer value was equal to.
254 */
255 if (read_cpuid_part() == ARM_CPU_PART_CORTEX_A9
256 && (read_cpuid_id() & 0xf0000f) < 0x200000) {
257 pr_warn("global-timer: non support for this cpu version.\n");
258 return;
259 }
260
261 gt_ppi = irq_of_parse_and_map(np, 0);
262 if (!gt_ppi) {
263 pr_warn("global-timer: unable to parse irq\n");
264 return;
265 }
266
267 gt_base = of_iomap(np, 0);
268 if (!gt_base) {
269 pr_warn("global-timer: invalid base address\n");
270 return;
271 }
272
273 gt_clk = of_clk_get(np, 0);
274 if (!IS_ERR(gt_clk)) {
275 err = clk_prepare_enable(gt_clk);
276 if (err)
277 goto out_unmap;
278 } else {
279 pr_warn("global-timer: clk not found\n");
280 err = -EINVAL;
281 goto out_unmap;
282 }
283
284 gt_clk_rate = clk_get_rate(gt_clk);
285 gt_evt = alloc_percpu(struct clock_event_device);
286 if (!gt_evt) {
287 pr_warn("global-timer: can't allocate memory\n");
288 err = -ENOMEM;
289 goto out_clk;
290 }
291
292 err = request_percpu_irq(gt_ppi, gt_clockevent_interrupt,
293 "gt", gt_evt);
294 if (err) {
295 pr_warn("global-timer: can't register interrupt %d (%d)\n",
296 gt_ppi, err);
297 goto out_free;
298 }
299
300 err = register_cpu_notifier(>_cpu_nb);
301 if (err) {
302 pr_warn("global-timer: unable to register cpu notifier.\n");
303 goto out_irq;
304 }
305
306 /* Immediately configure the timer on the boot CPU */
307 gt_clocksource_init();
308 gt_clockevents_init(this_cpu_ptr(gt_evt));
309
310 return;
311
312 out_irq:
313 free_percpu_irq(gt_ppi, gt_evt);
314 out_free:
315 free_percpu(gt_evt);
316 out_clk:
317 clk_disable_unprepare(gt_clk);
318 out_unmap:
319 iounmap(gt_base);
320 WARN(err, "ARM Global timer register failed (%d)\n", err);
321 }
322
323 /* Only tested on r2p2 and r3p0 */
324 CLOCKSOURCE_OF_DECLARE(arm_gt, "arm,cortex-a9-global-timer",
325 global_timer_of_register);
326