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 #include <asm/mach/time.h>
24 
25 #include <linux/of.h>
26 #include <linux/of_address.h>
27 #include <linux/of_irq.h>
28 
29 
30 #define KONA_GPTIMER_STCS_OFFSET			0x00000000
31 #define KONA_GPTIMER_STCLO_OFFSET			0x00000004
32 #define KONA_GPTIMER_STCHI_OFFSET			0x00000008
33 #define KONA_GPTIMER_STCM0_OFFSET			0x0000000C
34 
35 #define KONA_GPTIMER_STCS_TIMER_MATCH_SHIFT		0
36 #define KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT		4
37 
38 struct kona_bcm_timers {
39 	int tmr_irq;
40 	void __iomem *tmr_regs;
41 };
42 
43 static struct kona_bcm_timers timers;
44 
45 static u32 arch_timer_rate;
46 
47 /*
48  * We use the peripheral timers for system tick, the cpu global timer for
49  * profile tick
50  */
51 static void kona_timer_disable_and_clear(void __iomem *base)
52 {
53 	uint32_t reg;
54 
55 	/*
56 	 * clear and disable interrupts
57 	 * We are using compare/match register 0 for our system interrupts
58 	 */
59 	reg = readl(base + KONA_GPTIMER_STCS_OFFSET);
60 
61 	/* Clear compare (0) interrupt */
62 	reg |= 1 << KONA_GPTIMER_STCS_TIMER_MATCH_SHIFT;
63 	/* disable compare */
64 	reg &= ~(1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT);
65 
66 	writel(reg, base + KONA_GPTIMER_STCS_OFFSET);
67 
68 }
69 
70 static void
71 kona_timer_get_counter(void *timer_base, uint32_t *msw, uint32_t *lsw)
72 {
73 	void __iomem *base = IOMEM(timer_base);
74 	int loop_limit = 4;
75 
76 	/*
77 	 * Read 64-bit free running counter
78 	 * 1. Read hi-word
79 	 * 2. Read low-word
80 	 * 3. Read hi-word again
81 	 * 4.1
82 	 *      if new hi-word is not equal to previously read hi-word, then
83 	 *      start from #1
84 	 * 4.2
85 	 *      if new hi-word is equal to previously read hi-word then stop.
86 	 */
87 
88 	while (--loop_limit) {
89 		*msw = readl(base + KONA_GPTIMER_STCHI_OFFSET);
90 		*lsw = readl(base + KONA_GPTIMER_STCLO_OFFSET);
91 		if (*msw == readl(base + KONA_GPTIMER_STCHI_OFFSET))
92 			break;
93 	}
94 	if (!loop_limit) {
95 		pr_err("bcm_kona_timer: getting counter failed.\n");
96 		pr_err(" Timer will be impacted\n");
97 	}
98 
99 	return;
100 }
101 
102 static int kona_timer_set_next_event(unsigned long clc,
103 				  struct clock_event_device *unused)
104 {
105 	/*
106 	 * timer (0) is disabled by the timer interrupt already
107 	 * so, here we reload the next event value and re-enable
108 	 * the timer.
109 	 *
110 	 * This way, we are potentially losing the time between
111 	 * timer-interrupt->set_next_event. CPU local timers, when
112 	 * they come in should get rid of skew.
113 	 */
114 
115 	uint32_t lsw, msw;
116 	uint32_t reg;
117 
118 	kona_timer_get_counter(timers.tmr_regs, &msw, &lsw);
119 
120 	/* Load the "next" event tick value */
121 	writel(lsw + clc, timers.tmr_regs + KONA_GPTIMER_STCM0_OFFSET);
122 
123 	/* Enable compare */
124 	reg = readl(timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
125 	reg |= (1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT);
126 	writel(reg, timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
127 
128 	return 0;
129 }
130 
131 static void kona_timer_set_mode(enum clock_event_mode mode,
132 			     struct clock_event_device *unused)
133 {
134 	switch (mode) {
135 	case CLOCK_EVT_MODE_ONESHOT:
136 		/* by default mode is one shot don't do any thing */
137 		break;
138 	case CLOCK_EVT_MODE_UNUSED:
139 	case CLOCK_EVT_MODE_SHUTDOWN:
140 	default:
141 		kona_timer_disable_and_clear(timers.tmr_regs);
142 	}
143 }
144 
145 static struct clock_event_device kona_clockevent_timer = {
146 	.name = "timer 1",
147 	.features = CLOCK_EVT_FEAT_ONESHOT,
148 	.set_next_event = kona_timer_set_next_event,
149 	.set_mode = kona_timer_set_mode
150 };
151 
152 static void __init kona_timer_clockevents_init(void)
153 {
154 	kona_clockevent_timer.cpumask = cpumask_of(0);
155 	clockevents_config_and_register(&kona_clockevent_timer,
156 		arch_timer_rate, 6, 0xffffffff);
157 }
158 
159 static irqreturn_t kona_timer_interrupt(int irq, void *dev_id)
160 {
161 	struct clock_event_device *evt = &kona_clockevent_timer;
162 
163 	kona_timer_disable_and_clear(timers.tmr_regs);
164 	evt->event_handler(evt);
165 	return IRQ_HANDLED;
166 }
167 
168 static struct irqaction kona_timer_irq = {
169 	.name = "Kona Timer Tick",
170 	.flags = IRQF_TIMER,
171 	.handler = kona_timer_interrupt,
172 };
173 
174 static void __init kona_timer_init(struct device_node *node)
175 {
176 	u32 freq;
177 	struct clk *external_clk;
178 
179 	if (!of_device_is_available(node)) {
180 		pr_info("Kona Timer v1 marked as disabled in device tree\n");
181 		return;
182 	}
183 
184 	external_clk = of_clk_get_by_name(node, NULL);
185 
186 	if (!IS_ERR(external_clk)) {
187 		arch_timer_rate = clk_get_rate(external_clk);
188 		clk_prepare_enable(external_clk);
189 	} else if (!of_property_read_u32(node, "clock-frequency", &freq)) {
190 		arch_timer_rate = freq;
191 	} else {
192 		pr_err("Kona Timer v1 unable to determine clock-frequency");
193 		return;
194 	}
195 
196 	/* Setup IRQ numbers */
197 	timers.tmr_irq = irq_of_parse_and_map(node, 0);
198 
199 	/* Setup IO addresses */
200 	timers.tmr_regs = of_iomap(node, 0);
201 
202 	kona_timer_disable_and_clear(timers.tmr_regs);
203 
204 	kona_timer_clockevents_init();
205 	setup_irq(timers.tmr_irq, &kona_timer_irq);
206 	kona_timer_set_next_event((arch_timer_rate / HZ), NULL);
207 }
208 
209 CLOCKSOURCE_OF_DECLARE(brcm_kona, "brcm,kona-timer", kona_timer_init);
210 /*
211  * bcm,kona-timer is deprecated by brcm,kona-timer
212  * being kept here for driver compatibility
213  */
214 CLOCKSOURCE_OF_DECLARE(bcm_kona, "bcm,kona-timer", kona_timer_init);
215