1/*
  2 * This file is subject to the terms and conditions of the GNU General Public
  3 * License.  See the file "COPYING" in the main directory of this archive
  4 * for more details.
  5 *
  6 * Copyright (C) 2013 by John Crispin <john@phrozen.org>
  7 */
  8
  9#include <linux/clockchips.h>
 10#include <linux/clocksource.h>
 11#include <linux/interrupt.h>
 12#include <linux/reset.h>
 13#include <linux/init.h>
 14#include <linux/time.h>
 15#include <linux/of.h>
 16#include <linux/of_irq.h>
 17#include <linux/of_address.h>
 18
 19#include <asm/mach-ralink/ralink_regs.h>
 20
 21#define SYSTICK_FREQ		(50 * 1000)
 22
 23#define SYSTICK_CONFIG		0x00
 24#define SYSTICK_COMPARE		0x04
 25#define SYSTICK_COUNT		0x08
 26
 27/* route systick irq to mips irq 7 instead of the r4k-timer */
 28#define CFG_EXT_STK_EN		0x2
 29/* enable the counter */
 30#define CFG_CNT_EN		0x1
 31
 32struct systick_device {
 33	void __iomem *membase;
 34	struct clock_event_device dev;
 35	int irq_requested;
 36	int freq_scale;
 37};
 38
 39static int systick_set_oneshot(struct clock_event_device *evt);
 40static int systick_shutdown(struct clock_event_device *evt);
 41
 42static int systick_next_event(unsigned long delta,
 43				struct clock_event_device *evt)
 44{
 45	struct systick_device *sdev;
 46	u32 count;
 47
 48	sdev = container_of(evt, struct systick_device, dev);
 49	count = ioread32(sdev->membase + SYSTICK_COUNT);
 50	count = (count + delta) % SYSTICK_FREQ;
 51	iowrite32(count, sdev->membase + SYSTICK_COMPARE);
 52
 53	return 0;
 54}
 55
 56static void systick_event_handler(struct clock_event_device *dev)
 57{
 58	/* noting to do here */
 59}
 60
 61static irqreturn_t systick_interrupt(int irq, void *dev_id)
 62{
 63	struct clock_event_device *dev = (struct clock_event_device *) dev_id;
 64
 65	dev->event_handler(dev);
 66
 67	return IRQ_HANDLED;
 68}
 69
 70static struct systick_device systick = {
 71	.dev = {
 72		/*
 73		 * cevt-r4k uses 300, make sure systick
 74		 * gets used if available
 75		 */
 76		.rating			= 310,
 77		.features		= CLOCK_EVT_FEAT_ONESHOT,
 78		.set_next_event		= systick_next_event,
 79		.set_state_shutdown	= systick_shutdown,
 80		.set_state_oneshot	= systick_set_oneshot,
 81		.event_handler		= systick_event_handler,
 82	},
 83};
 84
 85static int systick_shutdown(struct clock_event_device *evt)
 86{
 87	struct systick_device *sdev;
 88
 89	sdev = container_of(evt, struct systick_device, dev);
 90
 91	if (sdev->irq_requested)
 92		free_irq(systick.dev.irq, &systick.dev);
 93	sdev->irq_requested = 0;
 94	iowrite32(0, systick.membase + SYSTICK_CONFIG);
 95
 96	return 0;
 97}
 98
 99static int systick_set_oneshot(struct clock_event_device *evt)
100{
101	const char *name = systick.dev.name;
102	struct systick_device *sdev;
103	int irq = systick.dev.irq;
104
105	sdev = container_of(evt, struct systick_device, dev);
106
107	if (!sdev->irq_requested) {
108		if (request_irq(irq, systick_interrupt,
109				IRQF_PERCPU | IRQF_TIMER, name, &systick.dev))
110			pr_err("Failed to request irq %d (%s)\n", irq, name);
111	}
112	sdev->irq_requested = 1;
113	iowrite32(CFG_EXT_STK_EN | CFG_CNT_EN,
114		  systick.membase + SYSTICK_CONFIG);
115
116	return 0;
117}
118
119static int __init ralink_systick_init(struct device_node *np)
120{
121	int ret;
122
123	systick.membase = of_iomap(np, 0);
124	if (!systick.membase)
125		return -ENXIO;
126
127	systick.dev.name = np->name;
128	clockevents_calc_mult_shift(&systick.dev, SYSTICK_FREQ, 60);
129	systick.dev.max_delta_ns = clockevent_delta2ns(0x7fff, &systick.dev);
130	systick.dev.max_delta_ticks = 0x7fff;
131	systick.dev.min_delta_ns = clockevent_delta2ns(0x3, &systick.dev);
132	systick.dev.min_delta_ticks = 0x3;
133	systick.dev.irq = irq_of_parse_and_map(np, 0);
134	if (!systick.dev.irq) {
135		pr_err("%pOFn: request_irq failed", np);
136		return -EINVAL;
137	}
138
139	ret = clocksource_mmio_init(systick.membase + SYSTICK_COUNT, np->name,
140				    SYSTICK_FREQ, 301, 16,
141				    clocksource_mmio_readl_up);
142	if (ret)
143		return ret;
144
145	clockevents_register_device(&systick.dev);
146
147	pr_info("%pOFn: running - mult: %d, shift: %d\n",
148			np, systick.dev.mult, systick.dev.shift);
149
150	return 0;
151}
152
153TIMER_OF_DECLARE(systick, "ralink,cevt-systick", ralink_systick_init);