1/*
  2 *  arch/arm/mach-vt8500/timer.c
  3 *
  4 *  Copyright (C) 2012 Tony Prisk <linux@prisktech.co.nz>
  5 *  Copyright (C) 2010 Alexey Charkov <alchark@gmail.com>
  6 *
  7 * This program is free software; you can redistribute it and/or modify
  8 * it under the terms of the GNU General Public License as published by
  9 * the Free Software Foundation; either version 2 of the License, or
 10 * (at your option) any later version.
 11 *
 12 * This program is distributed in the hope that it will be useful,
 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 15 * GNU General Public License for more details.
 16 *
 17 * You should have received a copy of the GNU General Public License
 18 * along with this program; if not, write to the Free Software
 19 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 20 */
 21
 22/*
 23 * This file is copied and modified from the original timer.c provided by
 24 * Alexey Charkov. Minor changes have been made for Device Tree Support.
 25 */
 26
 27#include <linux/io.h>
 28#include <linux/irq.h>
 29#include <linux/interrupt.h>
 30#include <linux/clocksource.h>
 31#include <linux/clockchips.h>
 32#include <linux/delay.h>
 33#include <asm/mach/time.h>
 34
 35#include <linux/of.h>
 36#include <linux/of_address.h>
 37#include <linux/of_irq.h>
 38
 39#define VT8500_TIMER_OFFSET	0x0100
 40#define VT8500_TIMER_HZ		3000000
 41#define TIMER_MATCH_VAL		0x0000
 42#define TIMER_COUNT_VAL		0x0010
 43#define TIMER_STATUS_VAL	0x0014
 44#define TIMER_IER_VAL		0x001c		/* interrupt enable */
 45#define TIMER_CTRL_VAL		0x0020
 46#define TIMER_AS_VAL		0x0024		/* access status */
 47#define TIMER_COUNT_R_ACTIVE	(1 << 5)	/* not ready for read */
 48#define TIMER_COUNT_W_ACTIVE	(1 << 4)	/* not ready for write */
 49#define TIMER_MATCH_W_ACTIVE	(1 << 0)	/* not ready for write */
 50
 51#define msecs_to_loops(t) (loops_per_jiffy / 1000 * HZ * t)
 52
 53static void __iomem *regbase;
 54
 55static cycle_t vt8500_timer_read(struct clocksource *cs)
 56{
 57	int loops = msecs_to_loops(10);
 58	writel(3, regbase + TIMER_CTRL_VAL);
 59	while ((readl((regbase + TIMER_AS_VAL)) & TIMER_COUNT_R_ACTIVE)
 60						&& --loops)
 61		cpu_relax();
 62	return readl(regbase + TIMER_COUNT_VAL);
 63}
 64
 65static struct clocksource clocksource = {
 66	.name           = "vt8500_timer",
 67	.rating         = 200,
 68	.read           = vt8500_timer_read,
 69	.mask           = CLOCKSOURCE_MASK(32),
 70	.flags          = CLOCK_SOURCE_IS_CONTINUOUS,
 71};
 72
 73static int vt8500_timer_set_next_event(unsigned long cycles,
 74				    struct clock_event_device *evt)
 75{
 76	int loops = msecs_to_loops(10);
 77	cycle_t alarm = clocksource.read(&clocksource) + cycles;
 78	while ((readl(regbase + TIMER_AS_VAL) & TIMER_MATCH_W_ACTIVE)
 79						&& --loops)
 80		cpu_relax();
 81	writel((unsigned long)alarm, regbase + TIMER_MATCH_VAL);
 82
 83	if ((signed)(alarm - clocksource.read(&clocksource)) <= 16)
 84		return -ETIME;
 85
 86	writel(1, regbase + TIMER_IER_VAL);
 87
 88	return 0;
 89}
 90
 91static void vt8500_timer_set_mode(enum clock_event_mode mode,
 92			      struct clock_event_device *evt)
 93{
 94	switch (mode) {
 95	case CLOCK_EVT_MODE_RESUME:
 96	case CLOCK_EVT_MODE_PERIODIC:
 97		break;
 98	case CLOCK_EVT_MODE_ONESHOT:
 99	case CLOCK_EVT_MODE_UNUSED:
100	case CLOCK_EVT_MODE_SHUTDOWN:
101		writel(readl(regbase + TIMER_CTRL_VAL) | 1,
102			regbase + TIMER_CTRL_VAL);
103		writel(0, regbase + TIMER_IER_VAL);
104		break;
105	}
106}
107
108static struct clock_event_device clockevent = {
109	.name           = "vt8500_timer",
110	.features       = CLOCK_EVT_FEAT_ONESHOT,
111	.rating         = 200,
112	.set_next_event = vt8500_timer_set_next_event,
113	.set_mode       = vt8500_timer_set_mode,
114};
115
116static irqreturn_t vt8500_timer_interrupt(int irq, void *dev_id)
117{
118	struct clock_event_device *evt = dev_id;
119	writel(0xf, regbase + TIMER_STATUS_VAL);
120	evt->event_handler(evt);
121
122	return IRQ_HANDLED;
123}
124
125static struct irqaction irq = {
126	.name    = "vt8500_timer",
127	.flags   = IRQF_TIMER | IRQF_IRQPOLL,
128	.handler = vt8500_timer_interrupt,
129	.dev_id  = &clockevent,
130};
131
132static void __init vt8500_timer_init(struct device_node *np)
133{
134	int timer_irq;
135
136	regbase = of_iomap(np, 0);
137	if (!regbase) {
138		pr_err("%s: Missing iobase description in Device Tree\n",
139								__func__);
140		return;
141	}
142	timer_irq = irq_of_parse_and_map(np, 0);
143	if (!timer_irq) {
144		pr_err("%s: Missing irq description in Device Tree\n",
145								__func__);
146		return;
147	}
148
149	writel(1, regbase + TIMER_CTRL_VAL);
150	writel(0xf, regbase + TIMER_STATUS_VAL);
151	writel(~0, regbase + TIMER_MATCH_VAL);
152
153	if (clocksource_register_hz(&clocksource, VT8500_TIMER_HZ))
154		pr_err("%s: vt8500_timer_init: clocksource_register failed for %s\n",
155					__func__, clocksource.name);
156
157	clockevent.cpumask = cpumask_of(0);
158
159	if (setup_irq(timer_irq, &irq))
160		pr_err("%s: setup_irq failed for %s\n", __func__,
161							clockevent.name);
162	clockevents_config_and_register(&clockevent, VT8500_TIMER_HZ,
163					4, 0xf0000000);
164}
165
166CLOCKSOURCE_OF_DECLARE(vt8500, "via,vt8500-timer", vt8500_timer_init);