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 int bcm2835_time_set_next_event(unsigned long event, 58 struct clock_event_device *evt_dev) 59 { 60 struct bcm2835_timer *timer = container_of(evt_dev, 61 struct bcm2835_timer, evt); 62 writel_relaxed(readl_relaxed(system_clock) + event, 63 timer->compare); 64 return 0; 65 } 66 67 static irqreturn_t bcm2835_time_interrupt(int irq, void *dev_id) 68 { 69 struct bcm2835_timer *timer = dev_id; 70 void (*event_handler)(struct clock_event_device *); 71 if (readl_relaxed(timer->control) & timer->match_mask) { 72 writel_relaxed(timer->match_mask, timer->control); 73 74 event_handler = ACCESS_ONCE(timer->evt.event_handler); 75 if (event_handler) 76 event_handler(&timer->evt); 77 return IRQ_HANDLED; 78 } else { 79 return IRQ_NONE; 80 } 81 } 82 83 static void __init bcm2835_timer_init(struct device_node *node) 84 { 85 void __iomem *base; 86 u32 freq; 87 int irq; 88 struct bcm2835_timer *timer; 89 90 base = of_iomap(node, 0); 91 if (!base) 92 panic("Can't remap registers"); 93 94 if (of_property_read_u32(node, "clock-frequency", &freq)) 95 panic("Can't read clock-frequency"); 96 97 system_clock = base + REG_COUNTER_LO; 98 sched_clock_register(bcm2835_sched_read, 32, freq); 99 100 clocksource_mmio_init(base + REG_COUNTER_LO, node->name, 101 freq, 300, 32, clocksource_mmio_readl_up); 102 103 irq = irq_of_parse_and_map(node, DEFAULT_TIMER); 104 if (irq <= 0) 105 panic("Can't parse IRQ"); 106 107 timer = kzalloc(sizeof(*timer), GFP_KERNEL); 108 if (!timer) 109 panic("Can't allocate timer struct\n"); 110 111 timer->control = base + REG_CONTROL; 112 timer->compare = base + REG_COMPARE(DEFAULT_TIMER); 113 timer->match_mask = BIT(DEFAULT_TIMER); 114 timer->evt.name = node->name; 115 timer->evt.rating = 300; 116 timer->evt.features = CLOCK_EVT_FEAT_ONESHOT; 117 timer->evt.set_next_event = bcm2835_time_set_next_event; 118 timer->evt.cpumask = cpumask_of(0); 119 timer->act.name = node->name; 120 timer->act.flags = IRQF_TIMER | IRQF_SHARED; 121 timer->act.dev_id = timer; 122 timer->act.handler = bcm2835_time_interrupt; 123 124 if (setup_irq(irq, &timer->act)) 125 panic("Can't set up timer IRQ\n"); 126 127 clockevents_config_and_register(&timer->evt, freq, 0xf, 0xffffffff); 128 129 pr_info("bcm2835: system timer (irq = %d)\n", irq); 130 } 131 CLOCKSOURCE_OF_DECLARE(bcm2835, "brcm,bcm2835-system-timer", 132 bcm2835_timer_init); 133