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
37struct kona_bcm_timers {
38 int tmr_irq;
39 void __iomem *tmr_regs;
40};
41
42static struct kona_bcm_timers timers;
43
44static u32 arch_timer_rate;
45
46/*
47 * We use the peripheral timers for system tick, the cpu global timer for
48 * profile tick
49 */
50static 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
69static int
70kona_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
101static 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
133static int kona_timer_shutdown(struct clock_event_device *evt)
134{
135 kona_timer_disable_and_clear(timers.tmr_regs);
136 return 0;
137}
138
139static 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
147static 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
154static 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
163static struct irqaction kona_timer_irq = {
164 .name = "Kona Timer Tick",
165 .flags = IRQF_TIMER,
166 .handler = kona_timer_interrupt,
167};
168
169static 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\n");
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
201TIMER_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 */
206TIMER_OF_DECLARE(bcm_kona, "bcm,kona-timer", kona_timer_init);
207