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Linux/drivers/clocksource/bcm2835_timer.c

  1 /*
  2  * Copyright 2012 Simon Arlott
  3  *
  4  * This program is free software; you can redistribute it and/or modify
  5  * it under the terms of the GNU General Public License as published by
  6  * the Free Software Foundation; either version 2 of the License, or
  7  * (at your option) any later version.
  8  *
  9  * This program is distributed in the hope that it will be useful,
 10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
 11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 12  * GNU General Public License for more details.
 13  *
 14  * You should have received a copy of the GNU General Public License
 15  * along with this program; if not, write to the Free Software
 16  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 17  */
 18 
 19 #include <linux/bitops.h>
 20 #include <linux/clockchips.h>
 21 #include <linux/clocksource.h>
 22 #include <linux/interrupt.h>
 23 #include <linux/irqreturn.h>
 24 #include <linux/kernel.h>
 25 #include <linux/module.h>
 26 #include <linux/of_address.h>
 27 #include <linux/of_irq.h>
 28 #include <linux/of_platform.h>
 29 #include <linux/slab.h>
 30 #include <linux/string.h>
 31 #include <linux/sched_clock.h>
 32 
 33 #include <asm/irq.h>
 34 
 35 #define REG_CONTROL     0x00
 36 #define REG_COUNTER_LO  0x04
 37 #define REG_COUNTER_HI  0x08
 38 #define REG_COMPARE(n)  (0x0c + (n) * 4)
 39 #define MAX_TIMER       3
 40 #define DEFAULT_TIMER   3
 41 
 42 struct bcm2835_timer {
 43         void __iomem *control;
 44         void __iomem *compare;
 45         int match_mask;
 46         struct clock_event_device evt;
 47         struct irqaction act;
 48 };
 49 
 50 static void __iomem *system_clock __read_mostly;
 51 
 52 static u64 notrace bcm2835_sched_read(void)
 53 {
 54         return readl_relaxed(system_clock);
 55 }
 56 
 57 static void bcm2835_time_set_mode(enum clock_event_mode mode,
 58         struct clock_event_device *evt_dev)
 59 {
 60         switch (mode) {
 61         case CLOCK_EVT_MODE_ONESHOT:
 62         case CLOCK_EVT_MODE_UNUSED:
 63         case CLOCK_EVT_MODE_SHUTDOWN:
 64         case CLOCK_EVT_MODE_RESUME:
 65                 break;
 66         default:
 67                 WARN(1, "%s: unhandled event mode %d\n", __func__, mode);
 68                 break;
 69         }
 70 }
 71 
 72 static int bcm2835_time_set_next_event(unsigned long event,
 73         struct clock_event_device *evt_dev)
 74 {
 75         struct bcm2835_timer *timer = container_of(evt_dev,
 76                 struct bcm2835_timer, evt);
 77         writel_relaxed(readl_relaxed(system_clock) + event,
 78                 timer->compare);
 79         return 0;
 80 }
 81 
 82 static irqreturn_t bcm2835_time_interrupt(int irq, void *dev_id)
 83 {
 84         struct bcm2835_timer *timer = dev_id;
 85         void (*event_handler)(struct clock_event_device *);
 86         if (readl_relaxed(timer->control) & timer->match_mask) {
 87                 writel_relaxed(timer->match_mask, timer->control);
 88 
 89                 event_handler = ACCESS_ONCE(timer->evt.event_handler);
 90                 if (event_handler)
 91                         event_handler(&timer->evt);
 92                 return IRQ_HANDLED;
 93         } else {
 94                 return IRQ_NONE;
 95         }
 96 }
 97 
 98 static void __init bcm2835_timer_init(struct device_node *node)
 99 {
100         void __iomem *base;
101         u32 freq;
102         int irq;
103         struct bcm2835_timer *timer;
104 
105         base = of_iomap(node, 0);
106         if (!base)
107                 panic("Can't remap registers");
108 
109         if (of_property_read_u32(node, "clock-frequency", &freq))
110                 panic("Can't read clock-frequency");
111 
112         system_clock = base + REG_COUNTER_LO;
113         sched_clock_register(bcm2835_sched_read, 32, freq);
114 
115         clocksource_mmio_init(base + REG_COUNTER_LO, node->name,
116                 freq, 300, 32, clocksource_mmio_readl_up);
117 
118         irq = irq_of_parse_and_map(node, DEFAULT_TIMER);
119         if (irq <= 0)
120                 panic("Can't parse IRQ");
121 
122         timer = kzalloc(sizeof(*timer), GFP_KERNEL);
123         if (!timer)
124                 panic("Can't allocate timer struct\n");
125 
126         timer->control = base + REG_CONTROL;
127         timer->compare = base + REG_COMPARE(DEFAULT_TIMER);
128         timer->match_mask = BIT(DEFAULT_TIMER);
129         timer->evt.name = node->name;
130         timer->evt.rating = 300;
131         timer->evt.features = CLOCK_EVT_FEAT_ONESHOT;
132         timer->evt.set_mode = bcm2835_time_set_mode;
133         timer->evt.set_next_event = bcm2835_time_set_next_event;
134         timer->evt.cpumask = cpumask_of(0);
135         timer->act.name = node->name;
136         timer->act.flags = IRQF_TIMER | IRQF_SHARED;
137         timer->act.dev_id = timer;
138         timer->act.handler = bcm2835_time_interrupt;
139 
140         if (setup_irq(irq, &timer->act))
141                 panic("Can't set up timer IRQ\n");
142 
143         clockevents_config_and_register(&timer->evt, freq, 0xf, 0xffffffff);
144 
145         pr_info("bcm2835: system timer (irq = %d)\n", irq);
146 }
147 CLOCKSOURCE_OF_DECLARE(bcm2835, "brcm,bcm2835-system-timer",
148                         bcm2835_timer_init);
149 

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