1// SPDX-License-Identifier: GPL-2.0
  2// Copyright (C) 2012 Broadcom Corporation
  3
  4#include <linux/init.h>
  5#include <linux/irq.h>
  6#include <linux/interrupt.h>
  7#include <linux/jiffies.h>
  8#include <linux/clockchips.h>
  9#include <linux/types.h>
 10#include <linux/clk.h>
 11
 12#include <linux/io.h>
 13
 14#include <linux/of.h>
 15#include <linux/of_address.h>
 16#include <linux/of_irq.h>
 17
 18
 19#define KONA_GPTIMER_STCS_OFFSET			0x00000000
 20#define KONA_GPTIMER_STCLO_OFFSET			0x00000004
 21#define KONA_GPTIMER_STCHI_OFFSET			0x00000008
 22#define KONA_GPTIMER_STCM0_OFFSET			0x0000000C
 23
 24#define KONA_GPTIMER_STCS_TIMER_MATCH_SHIFT		0
 25#define KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT		4
 26
 27struct kona_bcm_timers {
 28	int tmr_irq;
 29	void __iomem *tmr_regs;
 30};
 31
 32static struct kona_bcm_timers timers;
 33
 34static u32 arch_timer_rate;
 35
 36/*
 37 * We use the peripheral timers for system tick, the cpu global timer for
 38 * profile tick
 39 */
 40static void kona_timer_disable_and_clear(void __iomem *base)
 41{
 42	uint32_t reg;
 43
 44	/*
 45	 * clear and disable interrupts
 46	 * We are using compare/match register 0 for our system interrupts
 47	 */
 48	reg = readl(base + KONA_GPTIMER_STCS_OFFSET);
 49
 50	/* Clear compare (0) interrupt */
 51	reg |= 1 << KONA_GPTIMER_STCS_TIMER_MATCH_SHIFT;
 52	/* disable compare */
 53	reg &= ~(1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT);
 54
 55	writel(reg, base + KONA_GPTIMER_STCS_OFFSET);
 56
 57}
 58
 59static int
 60kona_timer_get_counter(void __iomem *timer_base, uint32_t *msw, uint32_t *lsw)
 61{
 62	int loop_limit = 3;
 63
 64	/*
 65	 * Read 64-bit free running counter
 66	 * 1. Read hi-word
 67	 * 2. Read low-word
 68	 * 3. Read hi-word again
 69	 * 4.1
 70	 *      if new hi-word is not equal to previously read hi-word, then
 71	 *      start from #1
 72	 * 4.2
 73	 *      if new hi-word is equal to previously read hi-word then stop.
 74	 */
 75
 76	do {
 77		*msw = readl(timer_base + KONA_GPTIMER_STCHI_OFFSET);
 78		*lsw = readl(timer_base + KONA_GPTIMER_STCLO_OFFSET);
 79		if (*msw == readl(timer_base + KONA_GPTIMER_STCHI_OFFSET))
 80			break;
 81	} while (--loop_limit);
 82	if (!loop_limit) {
 83		pr_err("bcm_kona_timer: getting counter failed.\n");
 84		pr_err(" Timer will be impacted\n");
 85		return -ETIMEDOUT;
 86	}
 87
 88	return 0;
 89}
 90
 91static int kona_timer_set_next_event(unsigned long clc,
 92				  struct clock_event_device *unused)
 93{
 94	/*
 95	 * timer (0) is disabled by the timer interrupt already
 96	 * so, here we reload the next event value and re-enable
 97	 * the timer.
 98	 *
 99	 * This way, we are potentially losing the time between
100	 * timer-interrupt->set_next_event. CPU local timers, when
101	 * they come in should get rid of skew.
102	 */
103
104	uint32_t lsw, msw;
105	uint32_t reg;
106	int ret;
107
108	ret = kona_timer_get_counter(timers.tmr_regs, &msw, &lsw);
109	if (ret)
110		return ret;
111
112	/* Load the "next" event tick value */
113	writel(lsw + clc, timers.tmr_regs + KONA_GPTIMER_STCM0_OFFSET);
114
115	/* Enable compare */
116	reg = readl(timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
117	reg |= (1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT);
118	writel(reg, timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
119
120	return 0;
121}
122
123static int kona_timer_shutdown(struct clock_event_device *evt)
124{
125	kona_timer_disable_and_clear(timers.tmr_regs);
126	return 0;
127}
128
129static struct clock_event_device kona_clockevent_timer = {
130	.name = "timer 1",
131	.features = CLOCK_EVT_FEAT_ONESHOT,
132	.set_next_event = kona_timer_set_next_event,
133	.set_state_shutdown = kona_timer_shutdown,
134	.tick_resume = kona_timer_shutdown,
135};
136
137static void __init kona_timer_clockevents_init(void)
138{
139	kona_clockevent_timer.cpumask = cpumask_of(0);
140	clockevents_config_and_register(&kona_clockevent_timer,
141		arch_timer_rate, 6, 0xffffffff);
142}
143
144static irqreturn_t kona_timer_interrupt(int irq, void *dev_id)
145{
146	struct clock_event_device *evt = &kona_clockevent_timer;
147
148	kona_timer_disable_and_clear(timers.tmr_regs);
149	evt->event_handler(evt);
150	return IRQ_HANDLED;
151}
152
153static int __init kona_timer_init(struct device_node *node)
154{
155	u32 freq;
156	struct clk *external_clk;
157
158	external_clk = of_clk_get_by_name(node, NULL);
159
160	if (!IS_ERR(external_clk)) {
161		arch_timer_rate = clk_get_rate(external_clk);
162		clk_prepare_enable(external_clk);
163	} else if (!of_property_read_u32(node, "clock-frequency", &freq)) {
164		arch_timer_rate = freq;
165	} else {
166		pr_err("Kona Timer v1 unable to determine clock-frequency\n");
167		return -EINVAL;
168	}
169
170	/* Setup IRQ numbers */
171	timers.tmr_irq = irq_of_parse_and_map(node, 0);
172
173	/* Setup IO addresses */
174	timers.tmr_regs = of_iomap(node, 0);
175
176	kona_timer_disable_and_clear(timers.tmr_regs);
177
178	kona_timer_clockevents_init();
179	if (request_irq(timers.tmr_irq, kona_timer_interrupt, IRQF_TIMER,
180			"Kona Timer Tick", NULL))
181		pr_err("%s: request_irq() failed\n", "Kona Timer Tick");
182	kona_timer_set_next_event((arch_timer_rate / HZ), NULL);
183
184	return 0;
185}
186
187TIMER_OF_DECLARE(brcm_kona, "brcm,kona-timer", kona_timer_init);
188/*
189 * bcm,kona-timer is deprecated by brcm,kona-timer
190 * being kept here for driver compatibility
191 */
192TIMER_OF_DECLARE(bcm_kona, "bcm,kona-timer", kona_timer_init);