1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Ralink System Tick Counter driver present on RT3352 and MT7620 SoCs.
  4 *
  5 * Copyright (C) 2013 by John Crispin <john@phrozen.org>
  6 */
  7
  8#include <linux/clockchips.h>
  9#include <linux/clocksource.h>
 10#include <linux/interrupt.h>
 11#include <linux/reset.h>
 12#include <linux/init.h>
 13#include <linux/time.h>
 14#include <linux/of.h>
 15#include <linux/of_irq.h>
 16#include <linux/of_address.h>
 17
 18#define SYSTICK_FREQ		(50 * 1000)
 19
 20#define SYSTICK_CONFIG		0x00
 21#define SYSTICK_COMPARE		0x04
 22#define SYSTICK_COUNT		0x08
 23
 24/* route systick irq to mips irq 7 instead of the r4k-timer */
 25#define CFG_EXT_STK_EN		0x2
 26/* enable the counter */
 27#define CFG_CNT_EN		0x1
 28
 29struct systick_device {
 30	void __iomem *membase;
 31	struct clock_event_device dev;
 32	int irq_requested;
 33	int freq_scale;
 34};
 35
 36static int systick_set_oneshot(struct clock_event_device *evt);
 37static int systick_shutdown(struct clock_event_device *evt);
 38
 39static int systick_next_event(unsigned long delta,
 40			      struct clock_event_device *evt)
 41{
 42	struct systick_device *sdev;
 43	u32 count;
 44
 45	sdev = container_of(evt, struct systick_device, dev);
 46	count = ioread32(sdev->membase + SYSTICK_COUNT);
 47	count = (count + delta) % SYSTICK_FREQ;
 48	iowrite32(count, sdev->membase + SYSTICK_COMPARE);
 49
 50	return 0;
 51}
 52
 53static void systick_event_handler(struct clock_event_device *dev)
 54{
 55	/* noting to do here */
 56}
 57
 58static irqreturn_t systick_interrupt(int irq, void *dev_id)
 59{
 60	struct clock_event_device *dev = (struct clock_event_device *)dev_id;
 61
 62	dev->event_handler(dev);
 63
 64	return IRQ_HANDLED;
 65}
 66
 67static struct systick_device systick = {
 68	.dev = {
 69		/*
 70		 * cevt-r4k uses 300, make sure systick
 71		 * gets used if available
 72		 */
 73		.rating			= 310,
 74		.features		= CLOCK_EVT_FEAT_ONESHOT,
 75		.set_next_event		= systick_next_event,
 76		.set_state_shutdown	= systick_shutdown,
 77		.set_state_oneshot	= systick_set_oneshot,
 78		.event_handler		= systick_event_handler,
 79	},
 80};
 81
 82static int systick_shutdown(struct clock_event_device *evt)
 83{
 84	struct systick_device *sdev;
 85
 86	sdev = container_of(evt, struct systick_device, dev);
 87
 88	if (sdev->irq_requested)
 89		free_irq(systick.dev.irq, &systick.dev);
 90	sdev->irq_requested = 0;
 91	iowrite32(0, systick.membase + SYSTICK_CONFIG);
 92
 93	return 0;
 94}
 95
 96static int systick_set_oneshot(struct clock_event_device *evt)
 97{
 98	const char *name = systick.dev.name;
 99	struct systick_device *sdev;
100	int irq = systick.dev.irq;
101
102	sdev = container_of(evt, struct systick_device, dev);
103
104	if (!sdev->irq_requested) {
105		if (request_irq(irq, systick_interrupt,
106				IRQF_PERCPU | IRQF_TIMER, name, &systick.dev))
107			pr_err("Failed to request irq %d (%s)\n", irq, name);
108	}
109	sdev->irq_requested = 1;
110	iowrite32(CFG_EXT_STK_EN | CFG_CNT_EN,
111		  systick.membase + SYSTICK_CONFIG);
112
113	return 0;
114}
115
116static int __init ralink_systick_init(struct device_node *np)
117{
118	int ret;
119
120	systick.membase = of_iomap(np, 0);
121	if (!systick.membase)
122		return -ENXIO;
123
124	systick.dev.name = np->name;
125	clockevents_calc_mult_shift(&systick.dev, SYSTICK_FREQ, 60);
126	systick.dev.max_delta_ns = clockevent_delta2ns(0x7fff, &systick.dev);
127	systick.dev.max_delta_ticks = 0x7fff;
128	systick.dev.min_delta_ns = clockevent_delta2ns(0x3, &systick.dev);
129	systick.dev.min_delta_ticks = 0x3;
130	systick.dev.irq = irq_of_parse_and_map(np, 0);
131	if (!systick.dev.irq) {
132		pr_err("%pOFn: request_irq failed", np);
133		return -EINVAL;
134	}
135
136	ret = clocksource_mmio_init(systick.membase + SYSTICK_COUNT, np->name,
137				    SYSTICK_FREQ, 301, 16,
138				    clocksource_mmio_readl_up);
139	if (ret)
140		return ret;
141
142	clockevents_register_device(&systick.dev);
143
144	pr_info("%pOFn: running - mult: %d, shift: %d\n",
145			np, systick.dev.mult, systick.dev.shift);
146
147	return 0;
148}
149
150TIMER_OF_DECLARE(systick, "ralink,cevt-systick", ralink_systick_init);