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
 34#include <linux/of.h>
 35#include <linux/of_address.h>
 36#include <linux/of_irq.h>
 37
 38#define VT8500_TIMER_OFFSET	0x0100
 39#define VT8500_TIMER_HZ		3000000
 40#define TIMER_MATCH_VAL		0x0000
 41#define TIMER_COUNT_VAL		0x0010
 42#define TIMER_STATUS_VAL	0x0014
 43#define TIMER_IER_VAL		0x001c		/* interrupt enable */
 44#define TIMER_CTRL_VAL		0x0020
 45#define TIMER_AS_VAL		0x0024		/* access status */
 46#define TIMER_COUNT_R_ACTIVE	(1 << 5)	/* not ready for read */
 47#define TIMER_COUNT_W_ACTIVE	(1 << 4)	/* not ready for write */
 48#define TIMER_MATCH_W_ACTIVE	(1 << 0)	/* not ready for write */
 49
 50#define msecs_to_loops(t) (loops_per_jiffy / 1000 * HZ * t)
 51
 52#define MIN_OSCR_DELTA		16
 53
 54static void __iomem *regbase;
 55
 56static cycle_t vt8500_timer_read(struct clocksource *cs)
 57{
 58	int loops = msecs_to_loops(10);
 59	writel(3, regbase + TIMER_CTRL_VAL);
 60	while ((readl((regbase + TIMER_AS_VAL)) & TIMER_COUNT_R_ACTIVE)
 61						&& --loops)
 62		cpu_relax();
 63	return readl(regbase + TIMER_COUNT_VAL);
 64}
 65
 66static struct clocksource clocksource = {
 67	.name           = "vt8500_timer",
 68	.rating         = 200,
 69	.read           = vt8500_timer_read,
 70	.mask           = CLOCKSOURCE_MASK(32),
 71	.flags          = CLOCK_SOURCE_IS_CONTINUOUS,
 72};
 73
 74static int vt8500_timer_set_next_event(unsigned long cycles,
 75				    struct clock_event_device *evt)
 76{
 77	int loops = msecs_to_loops(10);
 78	cycle_t alarm = clocksource.read(&clocksource) + cycles;
 79	while ((readl(regbase + TIMER_AS_VAL) & TIMER_MATCH_W_ACTIVE)
 80						&& --loops)
 81		cpu_relax();
 82	writel((unsigned long)alarm, regbase + TIMER_MATCH_VAL);
 83
 84	if ((signed)(alarm - clocksource.read(&clocksource)) <= MIN_OSCR_DELTA)
 85		return -ETIME;
 86
 87	writel(1, regbase + TIMER_IER_VAL);
 88
 89	return 0;
 90}
 91
 92static int vt8500_shutdown(struct clock_event_device *evt)
 93{
 94	writel(readl(regbase + TIMER_CTRL_VAL) | 1, regbase + TIMER_CTRL_VAL);
 95	writel(0, regbase + TIMER_IER_VAL);
 96	return 0;
 97}
 98
 99static struct clock_event_device clockevent = {
100	.name			= "vt8500_timer",
101	.features		= CLOCK_EVT_FEAT_ONESHOT,
102	.rating			= 200,
103	.set_next_event		= vt8500_timer_set_next_event,
104	.set_state_shutdown	= vt8500_shutdown,
105	.set_state_oneshot	= vt8500_shutdown,
106};
107
108static irqreturn_t vt8500_timer_interrupt(int irq, void *dev_id)
109{
110	struct clock_event_device *evt = dev_id;
111	writel(0xf, regbase + TIMER_STATUS_VAL);
112	evt->event_handler(evt);
113
114	return IRQ_HANDLED;
115}
116
117static struct irqaction irq = {
118	.name    = "vt8500_timer",
119	.flags   = IRQF_TIMER | IRQF_IRQPOLL,
120	.handler = vt8500_timer_interrupt,
121	.dev_id  = &clockevent,
122};
123
124static void __init vt8500_timer_init(struct device_node *np)
125{
126	int timer_irq;
127
128	regbase = of_iomap(np, 0);
129	if (!regbase) {
130		pr_err("%s: Missing iobase description in Device Tree\n",
131								__func__);
132		return;
133	}
134	timer_irq = irq_of_parse_and_map(np, 0);
135	if (!timer_irq) {
136		pr_err("%s: Missing irq description in Device Tree\n",
137								__func__);
138		return;
139	}
140
141	writel(1, regbase + TIMER_CTRL_VAL);
142	writel(0xf, regbase + TIMER_STATUS_VAL);
143	writel(~0, regbase + TIMER_MATCH_VAL);
144
145	if (clocksource_register_hz(&clocksource, VT8500_TIMER_HZ))
146		pr_err("%s: vt8500_timer_init: clocksource_register failed for %s\n",
147					__func__, clocksource.name);
148
149	clockevent.cpumask = cpumask_of(0);
150
151	if (setup_irq(timer_irq, &irq))
152		pr_err("%s: setup_irq failed for %s\n", __func__,
153							clockevent.name);
154	clockevents_config_and_register(&clockevent, VT8500_TIMER_HZ,
155					MIN_OSCR_DELTA * 2, 0xf0000000);
156}
157
158CLOCKSOURCE_OF_DECLARE(vt8500, "via,vt8500-timer", vt8500_timer_init);