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/bcm2835_timer.h> 20 #include <linux/bitops.h> 21 #include <linux/clockchips.h> 22 #include <linux/clocksource.h> 23 #include <linux/interrupt.h> 24 #include <linux/irqreturn.h> 25 #include <linux/kernel.h> 26 #include <linux/module.h> 27 #include <linux/of_address.h> 28 #include <linux/of_irq.h> 29 #include <linux/of_platform.h> 30 #include <linux/slab.h> 31 #include <linux/string.h> 32 33 #include <asm/sched_clock.h> 34 #include <asm/irq.h> 35 36 #define REG_CONTROL 0x00 37 #define REG_COUNTER_LO 0x04 38 #define REG_COUNTER_HI 0x08 39 #define REG_COMPARE(n) (0x0c + (n) * 4) 40 #define MAX_TIMER 3 41 #define DEFAULT_TIMER 3 42 43 struct bcm2835_timer { 44 void __iomem *control; 45 void __iomem *compare; 46 int match_mask; 47 struct clock_event_device evt; 48 struct irqaction act; 49 }; 50 51 static void __iomem *system_clock __read_mostly; 52 53 static u32 notrace bcm2835_sched_read(void) 54 { 55 return readl_relaxed(system_clock); 56 } 57 58 static void bcm2835_time_set_mode(enum clock_event_mode mode, 59 struct clock_event_device *evt_dev) 60 { 61 switch (mode) { 62 case CLOCK_EVT_MODE_ONESHOT: 63 case CLOCK_EVT_MODE_UNUSED: 64 case CLOCK_EVT_MODE_SHUTDOWN: 65 case CLOCK_EVT_MODE_RESUME: 66 break; 67 default: 68 WARN(1, "%s: unhandled event mode %d\n", __func__, mode); 69 break; 70 } 71 } 72 73 static int bcm2835_time_set_next_event(unsigned long event, 74 struct clock_event_device *evt_dev) 75 { 76 struct bcm2835_timer *timer = container_of(evt_dev, 77 struct bcm2835_timer, evt); 78 writel_relaxed(readl_relaxed(system_clock) + event, 79 timer->compare); 80 return 0; 81 } 82 83 static irqreturn_t bcm2835_time_interrupt(int irq, void *dev_id) 84 { 85 struct bcm2835_timer *timer = dev_id; 86 void (*event_handler)(struct clock_event_device *); 87 if (readl_relaxed(timer->control) & timer->match_mask) { 88 writel_relaxed(timer->match_mask, timer->control); 89 90 event_handler = ACCESS_ONCE(timer->evt.event_handler); 91 if (event_handler) 92 event_handler(&timer->evt); 93 return IRQ_HANDLED; 94 } else { 95 return IRQ_NONE; 96 } 97 } 98 99 static struct of_device_id bcm2835_time_match[] __initconst = { 100 { .compatible = "brcm,bcm2835-system-timer" }, 101 {} 102 }; 103 104 static void __init bcm2835_time_init(void) 105 { 106 struct device_node *node; 107 void __iomem *base; 108 u32 freq; 109 int irq; 110 struct bcm2835_timer *timer; 111 112 node = of_find_matching_node(NULL, bcm2835_time_match); 113 if (!node) 114 panic("No bcm2835 timer node"); 115 116 base = of_iomap(node, 0); 117 if (!base) 118 panic("Can't remap registers"); 119 120 if (of_property_read_u32(node, "clock-frequency", &freq)) 121 panic("Can't read clock-frequency"); 122 123 system_clock = base + REG_COUNTER_LO; 124 setup_sched_clock(bcm2835_sched_read, 32, freq); 125 126 clocksource_mmio_init(base + REG_COUNTER_LO, node->name, 127 freq, 300, 32, clocksource_mmio_readl_up); 128 129 irq = irq_of_parse_and_map(node, DEFAULT_TIMER); 130 if (irq <= 0) 131 panic("Can't parse IRQ"); 132 133 timer = kzalloc(sizeof(*timer), GFP_KERNEL); 134 if (!timer) 135 panic("Can't allocate timer struct\n"); 136 137 timer->control = base + REG_CONTROL; 138 timer->compare = base + REG_COMPARE(DEFAULT_TIMER); 139 timer->match_mask = BIT(DEFAULT_TIMER); 140 timer->evt.name = node->name; 141 timer->evt.rating = 300; 142 timer->evt.features = CLOCK_EVT_FEAT_ONESHOT; 143 timer->evt.set_mode = bcm2835_time_set_mode; 144 timer->evt.set_next_event = bcm2835_time_set_next_event; 145 timer->evt.cpumask = cpumask_of(0); 146 timer->act.name = node->name; 147 timer->act.flags = IRQF_TIMER | IRQF_SHARED; 148 timer->act.dev_id = timer; 149 timer->act.handler = bcm2835_time_interrupt; 150 151 if (setup_irq(irq, &timer->act)) 152 panic("Can't set up timer IRQ\n"); 153 154 clockevents_config_and_register(&timer->evt, freq, 0xf, 0xffffffff); 155 156 pr_info("bcm2835: system timer (irq = %d)\n", irq); 157 } 158 159 struct sys_timer bcm2835_timer = { 160 .init = bcm2835_time_init, 161 }; 162