1 // SPDX-License-Identifier: GPL-2.0+ 2 /* 3 * Copyright 2012 Simon Arlott 4 */ 5 6 #include <linux/bitops.h> 7 #include <linux/clockchips.h> 8 #include <linux/clocksource.h> 9 #include <linux/interrupt.h> 10 #include <linux/irqreturn.h> 11 #include <linux/kernel.h> 12 #include <linux/module.h> 13 #include <linux/of_address.h> 14 #include <linux/of_irq.h> 15 #include <linux/of_platform.h> 16 #include <linux/slab.h> 17 #include <linux/string.h> 18 #include <linux/sched_clock.h> 19 20 #include <asm/irq.h> 21 22 #define REG_CONTROL 0x00 23 #define REG_COUNTER_LO 0x04 24 #define REG_COUNTER_HI 0x08 25 #define REG_COMPARE(n) (0x0c + (n) * 4) 26 #define MAX_TIMER 3 27 #define DEFAULT_TIMER 3 28 29 struct bcm2835_timer { 30 void __iomem *control; 31 void __iomem *compare; 32 int match_mask; 33 struct clock_event_device evt; 34 }; 35 36 static void __iomem *system_clock __read_mostly; 37 38 static u64 notrace bcm2835_sched_read(void) 39 { 40 return readl_relaxed(system_clock); 41 } 42 43 static int bcm2835_time_set_next_event(unsigned long event, 44 struct clock_event_device *evt_dev) 45 { 46 struct bcm2835_timer *timer = container_of(evt_dev, 47 struct bcm2835_timer, evt); 48 writel_relaxed(readl_relaxed(system_clock) + event, 49 timer->compare); 50 return 0; 51 } 52 53 static irqreturn_t bcm2835_time_interrupt(int irq, void *dev_id) 54 { 55 struct bcm2835_timer *timer = dev_id; 56 void (*event_handler)(struct clock_event_device *); 57 if (readl_relaxed(timer->control) & timer->match_mask) { 58 writel_relaxed(timer->match_mask, timer->control); 59 60 event_handler = READ_ONCE(timer->evt.event_handler); 61 if (event_handler) 62 event_handler(&timer->evt); 63 return IRQ_HANDLED; 64 } else { 65 return IRQ_NONE; 66 } 67 } 68 69 static int __init bcm2835_timer_init(struct device_node *node) 70 { 71 void __iomem *base; 72 u32 freq; 73 int irq, ret; 74 struct bcm2835_timer *timer; 75 76 base = of_iomap(node, 0); 77 if (!base) { 78 pr_err("Can't remap registers\n"); 79 return -ENXIO; 80 } 81 82 ret = of_property_read_u32(node, "clock-frequency", &freq); 83 if (ret) { 84 pr_err("Can't read clock-frequency\n"); 85 goto err_iounmap; 86 } 87 88 system_clock = base + REG_COUNTER_LO; 89 sched_clock_register(bcm2835_sched_read, 32, freq); 90 91 clocksource_mmio_init(base + REG_COUNTER_LO, node->name, 92 freq, 300, 32, clocksource_mmio_readl_up); 93 94 irq = irq_of_parse_and_map(node, DEFAULT_TIMER); 95 if (irq <= 0) { 96 pr_err("Can't parse IRQ\n"); 97 ret = -EINVAL; 98 goto err_iounmap; 99 } 100 101 timer = kzalloc(sizeof(*timer), GFP_KERNEL); 102 if (!timer) { 103 ret = -ENOMEM; 104 goto err_iounmap; 105 } 106 107 timer->control = base + REG_CONTROL; 108 timer->compare = base + REG_COMPARE(DEFAULT_TIMER); 109 timer->match_mask = BIT(DEFAULT_TIMER); 110 timer->evt.name = node->name; 111 timer->evt.rating = 300; 112 timer->evt.features = CLOCK_EVT_FEAT_ONESHOT; 113 timer->evt.set_next_event = bcm2835_time_set_next_event; 114 timer->evt.cpumask = cpumask_of(0); 115 116 ret = request_irq(irq, bcm2835_time_interrupt, IRQF_TIMER | IRQF_SHARED, 117 node->name, timer); 118 if (ret) { 119 pr_err("Can't set up timer IRQ\n"); 120 goto err_timer_free; 121 } 122 123 clockevents_config_and_register(&timer->evt, freq, 0xf, 0xffffffff); 124 125 pr_info("bcm2835: system timer (irq = %d)\n", irq); 126 127 return 0; 128 129 err_timer_free: 130 kfree(timer); 131 132 err_iounmap: 133 iounmap(base); 134 return ret; 135 } 136 TIMER_OF_DECLARE(bcm2835, "brcm,bcm2835-system-timer", 137 bcm2835_timer_init); 138