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 <blogic@openwrt.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 struct irqaction systick_irqaction = {
 86	.handler = systick_interrupt,
 87	.flags = IRQF_PERCPU | IRQF_TIMER,
 88	.dev_id = &systick.dev,
 89};
 90
 91static int systick_shutdown(struct clock_event_device *evt)
 92{
 93	struct systick_device *sdev;
 94
 95	sdev = container_of(evt, struct systick_device, dev);
 96
 97	if (sdev->irq_requested)
 98		free_irq(systick.dev.irq, &systick_irqaction);
 99	sdev->irq_requested = 0;
100	iowrite32(0, systick.membase + SYSTICK_CONFIG);
101
102	return 0;
103}
104
105static int systick_set_oneshot(struct clock_event_device *evt)
106{
107	struct systick_device *sdev;
108
109	sdev = container_of(evt, struct systick_device, dev);
110
111	if (!sdev->irq_requested)
112		setup_irq(systick.dev.irq, &systick_irqaction);
113	sdev->irq_requested = 1;
114	iowrite32(CFG_EXT_STK_EN | CFG_CNT_EN,
115		  systick.membase + SYSTICK_CONFIG);
116
117	return 0;
118}
119
120static void __init ralink_systick_init(struct device_node *np)
121{
122	systick.membase = of_iomap(np, 0);
123	if (!systick.membase)
124		return;
125
126	systick_irqaction.name = np->name;
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.min_delta_ns = clockevent_delta2ns(0x3, &systick.dev);
131	systick.dev.irq = irq_of_parse_and_map(np, 0);
132	if (!systick.dev.irq) {
133		pr_err("%s: request_irq failed", np->name);
134		return;
135	}
136
137	clocksource_mmio_init(systick.membase + SYSTICK_COUNT, np->name,
138			SYSTICK_FREQ, 301, 16, clocksource_mmio_readl_up);
139
140	clockevents_register_device(&systick.dev);
141
142	pr_info("%s: running - mult: %d, shift: %d\n",
143			np->name, systick.dev.mult, systick.dev.shift);
144}
145
146CLOCKSOURCE_OF_DECLARE(systick, "ralink,cevt-systick", ralink_systick_init);