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 */
50static void __iomem *gt_base;
51static unsigned long gt_clk_rate;
52static int gt_ppi;
53static 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 */
63static u64 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
82/**
83 * To ensure that updates to comparator value register do not set the
84 * Interrupt Status Register proceed as follows:
85 * 1. Clear the Comp Enable bit in the Timer Control Register.
86 * 2. Write the lower 32-bit Comparator Value Register.
87 * 3. Write the upper 32-bit Comparator Value Register.
88 * 4. Set the Comp Enable bit and, if necessary, the IRQ enable bit.
89 */
90static void gt_compare_set(unsigned long delta, int periodic)
91{
92	u64 counter = gt_counter_read();
93	unsigned long ctrl;
94
95	counter += delta;
96	ctrl = GT_CONTROL_TIMER_ENABLE;
97	writel(ctrl, gt_base + GT_CONTROL);
98	writel(lower_32_bits(counter), gt_base + GT_COMP0);
99	writel(upper_32_bits(counter), gt_base + GT_COMP1);
100
101	if (periodic) {
102		writel(delta, gt_base + GT_AUTO_INC);
103		ctrl |= GT_CONTROL_AUTO_INC;
104	}
105
106	ctrl |= GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE;
107	writel(ctrl, gt_base + GT_CONTROL);
108}
109
110static void gt_clockevent_set_mode(enum clock_event_mode mode,
111				   struct clock_event_device *clk)
112{
113	unsigned long ctrl;
114
115	switch (mode) {
116	case CLOCK_EVT_MODE_PERIODIC:
117		gt_compare_set(DIV_ROUND_CLOSEST(gt_clk_rate, HZ), 1);
118		break;
119	case CLOCK_EVT_MODE_ONESHOT:
120	case CLOCK_EVT_MODE_UNUSED:
121	case CLOCK_EVT_MODE_SHUTDOWN:
122		ctrl = readl(gt_base + GT_CONTROL);
123		ctrl &= ~(GT_CONTROL_COMP_ENABLE |
124				GT_CONTROL_IRQ_ENABLE | GT_CONTROL_AUTO_INC);
125		writel(ctrl, gt_base + GT_CONTROL);
126		break;
127	default:
128		break;
129	}
130}
131
132static 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
139static 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 (evt->mode == CLOCK_EVT_MODE_ONESHOT)
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
167static 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_mode = gt_clockevent_set_mode;
175	clk->set_next_event = gt_clockevent_set_next_event;
176	clk->cpumask = cpumask_of(cpu);
177	clk->rating = 300;
178	clk->irq = gt_ppi;
179	clockevents_config_and_register(clk, gt_clk_rate,
180					1, 0xffffffff);
181	enable_percpu_irq(clk->irq, IRQ_TYPE_NONE);
182	return 0;
183}
184
185static void gt_clockevents_stop(struct clock_event_device *clk)
186{
187	gt_clockevent_set_mode(CLOCK_EVT_MODE_UNUSED, clk);
188	disable_percpu_irq(clk->irq);
189}
190
191static cycle_t gt_clocksource_read(struct clocksource *cs)
192{
193	return gt_counter_read();
194}
195
196static struct clocksource gt_clocksource = {
197	.name	= "arm_global_timer",
198	.rating	= 300,
199	.read	= gt_clocksource_read,
200	.mask	= CLOCKSOURCE_MASK(64),
201	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
202};
203
204#ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
205static u64 notrace gt_sched_clock_read(void)
206{
207	return gt_counter_read();
208}
209#endif
210
211static void __init gt_clocksource_init(void)
212{
213	writel(0, gt_base + GT_CONTROL);
214	writel(0, gt_base + GT_COUNTER0);
215	writel(0, gt_base + GT_COUNTER1);
216	/* enables timer on all the cores */
217	writel(GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL);
218
219#ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
220	sched_clock_register(gt_sched_clock_read, 64, gt_clk_rate);
221#endif
222	clocksource_register_hz(&gt_clocksource, gt_clk_rate);
223}
224
225static int gt_cpu_notify(struct notifier_block *self, unsigned long action,
226			 void *hcpu)
227{
228	switch (action & ~CPU_TASKS_FROZEN) {
229	case CPU_STARTING:
230		gt_clockevents_init(this_cpu_ptr(gt_evt));
231		break;
232	case CPU_DYING:
233		gt_clockevents_stop(this_cpu_ptr(gt_evt));
234		break;
235	}
236
237	return NOTIFY_OK;
238}
239static struct notifier_block gt_cpu_nb = {
240	.notifier_call = gt_cpu_notify,
241};
242
243static void __init global_timer_of_register(struct device_node *np)
244{
245	struct clk *gt_clk;
246	int err = 0;
247
248	/*
249	 * In A9 r2p0 the comparators for each processor with the global timer
250	 * fire when the timer value is greater than or equal to. In previous
251	 * revisions the comparators fired when the timer value was equal to.
252	 */
253	if (read_cpuid_part() == ARM_CPU_PART_CORTEX_A9
254	    && (read_cpuid_id() & 0xf0000f) < 0x200000) {
255		pr_warn("global-timer: non support for this cpu version.\n");
256		return;
257	}
258
259	gt_ppi = irq_of_parse_and_map(np, 0);
260	if (!gt_ppi) {
261		pr_warn("global-timer: unable to parse irq\n");
262		return;
263	}
264
265	gt_base = of_iomap(np, 0);
266	if (!gt_base) {
267		pr_warn("global-timer: invalid base address\n");
268		return;
269	}
270
271	gt_clk = of_clk_get(np, 0);
272	if (!IS_ERR(gt_clk)) {
273		err = clk_prepare_enable(gt_clk);
274		if (err)
275			goto out_unmap;
276	} else {
277		pr_warn("global-timer: clk not found\n");
278		err = -EINVAL;
279		goto out_unmap;
280	}
281
282	gt_clk_rate = clk_get_rate(gt_clk);
283	gt_evt = alloc_percpu(struct clock_event_device);
284	if (!gt_evt) {
285		pr_warn("global-timer: can't allocate memory\n");
286		err = -ENOMEM;
287		goto out_clk;
288	}
289
290	err = request_percpu_irq(gt_ppi, gt_clockevent_interrupt,
291				 "gt", gt_evt);
292	if (err) {
293		pr_warn("global-timer: can't register interrupt %d (%d)\n",
294			gt_ppi, err);
295		goto out_free;
296	}
297
298	err = register_cpu_notifier(&gt_cpu_nb);
299	if (err) {
300		pr_warn("global-timer: unable to register cpu notifier.\n");
301		goto out_irq;
302	}
303
304	/* Immediately configure the timer on the boot CPU */
305	gt_clocksource_init();
306	gt_clockevents_init(this_cpu_ptr(gt_evt));
307
308	return;
309
310out_irq:
311	free_percpu_irq(gt_ppi, gt_evt);
312out_free:
313	free_percpu(gt_evt);
314out_clk:
315	clk_disable_unprepare(gt_clk);
316out_unmap:
317	iounmap(gt_base);
318	WARN(err, "ARM Global timer register failed (%d)\n", err);
319}
320
321/* Only tested on r2p2 and r3p0  */
322CLOCKSOURCE_OF_DECLARE(arm_gt, "arm,cortex-a9-global-timer",
323			global_timer_of_register);
324