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 int __init kona_timer_init(struct device_node *node)
164{
165	u32 freq;
166	struct clk *external_clk;
167
168	external_clk = of_clk_get_by_name(node, NULL);
169
170	if (!IS_ERR(external_clk)) {
171		arch_timer_rate = clk_get_rate(external_clk);
172		clk_prepare_enable(external_clk);
173	} else if (!of_property_read_u32(node, "clock-frequency", &freq)) {
174		arch_timer_rate = freq;
175	} else {
176		pr_err("Kona Timer v1 unable to determine clock-frequency\n");
177		return -EINVAL;
178	}
179
180	/* Setup IRQ numbers */
181	timers.tmr_irq = irq_of_parse_and_map(node, 0);
182
183	/* Setup IO addresses */
184	timers.tmr_regs = of_iomap(node, 0);
185
186	kona_timer_disable_and_clear(timers.tmr_regs);
187
188	kona_timer_clockevents_init();
189	if (request_irq(timers.tmr_irq, kona_timer_interrupt, IRQF_TIMER,
190			"Kona Timer Tick", NULL))
191		pr_err("%s: request_irq() failed\n", "Kona Timer Tick");
192	kona_timer_set_next_event((arch_timer_rate / HZ), NULL);
193
194	return 0;
195}
196
197TIMER_OF_DECLARE(brcm_kona, "brcm,kona-timer", kona_timer_init);
198/*
199 * bcm,kona-timer is deprecated by brcm,kona-timer
200 * being kept here for driver compatibility
201 */
202TIMER_OF_DECLARE(bcm_kona, "bcm,kona-timer", kona_timer_init);
203