1 /*
2  * Copyright (C) 2012 Broadcom Corporation
3  *
4  * This program is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU General Public License as
6  * published by the Free Software Foundation version 2.
7  *
8  * This program is distributed "as is" WITHOUT ANY WARRANTY of any
9  * kind, whether express or implied; without even the implied warranty
10  * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
11  * GNU General Public License for more details.
12  */
13 
14 #include <linux/init.h>
15 #include <linux/irq.h>
16 #include <linux/interrupt.h>
17 #include <linux/jiffies.h>
18 #include <linux/clockchips.h>
19 #include <linux/types.h>
20 #include <linux/clk.h>
21 
22 #include <linux/io.h>
23 
24 #include <linux/of.h>
25 #include <linux/of_address.h>
26 #include <linux/of_irq.h>
27 
28 
29 #define KONA_GPTIMER_STCS_OFFSET			0x00000000
30 #define KONA_GPTIMER_STCLO_OFFSET			0x00000004
31 #define KONA_GPTIMER_STCHI_OFFSET			0x00000008
32 #define KONA_GPTIMER_STCM0_OFFSET			0x0000000C
33 
34 #define KONA_GPTIMER_STCS_TIMER_MATCH_SHIFT		0
35 #define KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT		4
36 
37 struct kona_bcm_timers {
38 	int tmr_irq;
39 	void __iomem *tmr_regs;
40 };
41 
42 static struct kona_bcm_timers timers;
43 
44 static u32 arch_timer_rate;
45 
46 /*
47  * We use the peripheral timers for system tick, the cpu global timer for
48  * profile tick
49  */
50 static void kona_timer_disable_and_clear(void __iomem *base)
51 {
52 	uint32_t reg;
53 
54 	/*
55 	 * clear and disable interrupts
56 	 * We are using compare/match register 0 for our system interrupts
57 	 */
58 	reg = readl(base + KONA_GPTIMER_STCS_OFFSET);
59 
60 	/* Clear compare (0) interrupt */
61 	reg |= 1 << KONA_GPTIMER_STCS_TIMER_MATCH_SHIFT;
62 	/* disable compare */
63 	reg &= ~(1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT);
64 
65 	writel(reg, base + KONA_GPTIMER_STCS_OFFSET);
66 
67 }
68 
69 static int
70 kona_timer_get_counter(void __iomem *timer_base, uint32_t *msw, uint32_t *lsw)
71 {
72 	int loop_limit = 3;
73 
74 	/*
75 	 * Read 64-bit free running counter
76 	 * 1. Read hi-word
77 	 * 2. Read low-word
78 	 * 3. Read hi-word again
79 	 * 4.1
80 	 *      if new hi-word is not equal to previously read hi-word, then
81 	 *      start from #1
82 	 * 4.2
83 	 *      if new hi-word is equal to previously read hi-word then stop.
84 	 */
85 
86 	do {
87 		*msw = readl(timer_base + KONA_GPTIMER_STCHI_OFFSET);
88 		*lsw = readl(timer_base + KONA_GPTIMER_STCLO_OFFSET);
89 		if (*msw == readl(timer_base + KONA_GPTIMER_STCHI_OFFSET))
90 			break;
91 	} while (--loop_limit);
92 	if (!loop_limit) {
93 		pr_err("bcm_kona_timer: getting counter failed.\n");
94 		pr_err(" Timer will be impacted\n");
95 		return -ETIMEDOUT;
96 	}
97 
98 	return 0;
99 }
100 
101 static int kona_timer_set_next_event(unsigned long clc,
102 				  struct clock_event_device *unused)
103 {
104 	/*
105 	 * timer (0) is disabled by the timer interrupt already
106 	 * so, here we reload the next event value and re-enable
107 	 * the timer.
108 	 *
109 	 * This way, we are potentially losing the time between
110 	 * timer-interrupt->set_next_event. CPU local timers, when
111 	 * they come in should get rid of skew.
112 	 */
113 
114 	uint32_t lsw, msw;
115 	uint32_t reg;
116 	int ret;
117 
118 	ret = kona_timer_get_counter(timers.tmr_regs, &msw, &lsw);
119 	if (ret)
120 		return ret;
121 
122 	/* Load the "next" event tick value */
123 	writel(lsw + clc, timers.tmr_regs + KONA_GPTIMER_STCM0_OFFSET);
124 
125 	/* Enable compare */
126 	reg = readl(timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
127 	reg |= (1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT);
128 	writel(reg, timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
129 
130 	return 0;
131 }
132 
133 static int kona_timer_shutdown(struct clock_event_device *evt)
134 {
135 	kona_timer_disable_and_clear(timers.tmr_regs);
136 	return 0;
137 }
138 
139 static struct clock_event_device kona_clockevent_timer = {
140 	.name = "timer 1",
141 	.features = CLOCK_EVT_FEAT_ONESHOT,
142 	.set_next_event = kona_timer_set_next_event,
143 	.set_state_shutdown = kona_timer_shutdown,
144 	.tick_resume = kona_timer_shutdown,
145 };
146 
147 static void __init kona_timer_clockevents_init(void)
148 {
149 	kona_clockevent_timer.cpumask = cpumask_of(0);
150 	clockevents_config_and_register(&kona_clockevent_timer,
151 		arch_timer_rate, 6, 0xffffffff);
152 }
153 
154 static irqreturn_t kona_timer_interrupt(int irq, void *dev_id)
155 {
156 	struct clock_event_device *evt = &kona_clockevent_timer;
157 
158 	kona_timer_disable_and_clear(timers.tmr_regs);
159 	evt->event_handler(evt);
160 	return IRQ_HANDLED;
161 }
162 
163 static struct irqaction kona_timer_irq = {
164 	.name = "Kona Timer Tick",
165 	.flags = IRQF_TIMER,
166 	.handler = kona_timer_interrupt,
167 };
168 
169 static int __init kona_timer_init(struct device_node *node)
170 {
171 	u32 freq;
172 	struct clk *external_clk;
173 
174 	external_clk = of_clk_get_by_name(node, NULL);
175 
176 	if (!IS_ERR(external_clk)) {
177 		arch_timer_rate = clk_get_rate(external_clk);
178 		clk_prepare_enable(external_clk);
179 	} else if (!of_property_read_u32(node, "clock-frequency", &freq)) {
180 		arch_timer_rate = freq;
181 	} else {
182 		pr_err("Kona Timer v1 unable to determine clock-frequency");
183 		return -EINVAL;
184 	}
185 
186 	/* Setup IRQ numbers */
187 	timers.tmr_irq = irq_of_parse_and_map(node, 0);
188 
189 	/* Setup IO addresses */
190 	timers.tmr_regs = of_iomap(node, 0);
191 
192 	kona_timer_disable_and_clear(timers.tmr_regs);
193 
194 	kona_timer_clockevents_init();
195 	setup_irq(timers.tmr_irq, &kona_timer_irq);
196 	kona_timer_set_next_event((arch_timer_rate / HZ), NULL);
197 
198 	return 0;
199 }
200 
201 CLOCKSOURCE_OF_DECLARE(brcm_kona, "brcm,kona-timer", kona_timer_init);
202 /*
203  * bcm,kona-timer is deprecated by brcm,kona-timer
204  * being kept here for driver compatibility
205  */
206 CLOCKSOURCE_OF_DECLARE(bcm_kona, "bcm,kona-timer", kona_timer_init);
207