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