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| 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 | +}; |
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