1 /* 2 * This file is subject to the terms and conditions of the GNU General Public 3 * License. See the file "COPYING" in the main directory of this archive 4 * for more details. 5 * 6 * Copyright (C) 2013 by John Crispin <john@phrozen.org> 7 */ 8 9 #include <linux/clockchips.h> 10 #include <linux/clocksource.h> 11 #include <linux/interrupt.h> 12 #include <linux/reset.h> 13 #include <linux/init.h> 14 #include <linux/time.h> 15 #include <linux/of.h> 16 #include <linux/of_irq.h> 17 #include <linux/of_address.h> 18 19 #include <asm/mach-ralink/ralink_regs.h> 20 21 #define SYSTICK_FREQ (50 * 1000) 22 23 #define SYSTICK_CONFIG 0x00 24 #define SYSTICK_COMPARE 0x04 25 #define SYSTICK_COUNT 0x08 26 27 /* route systick irq to mips irq 7 instead of the r4k-timer */ 28 #define CFG_EXT_STK_EN 0x2 29 /* enable the counter */ 30 #define CFG_CNT_EN 0x1 31 32 struct systick_device { 33 void __iomem *membase; 34 struct clock_event_device dev; 35 int irq_requested; 36 int freq_scale; 37 }; 38 39 static int systick_set_oneshot(struct clock_event_device *evt); 40 static int systick_shutdown(struct clock_event_device *evt); 41 42 static int systick_next_event(unsigned long delta, 43 struct clock_event_device *evt) 44 { 45 struct systick_device *sdev; 46 u32 count; 47 48 sdev = container_of(evt, struct systick_device, dev); 49 count = ioread32(sdev->membase + SYSTICK_COUNT); 50 count = (count + delta) % SYSTICK_FREQ; 51 iowrite32(count, sdev->membase + SYSTICK_COMPARE); 52 53 return 0; 54 } 55 56 static void systick_event_handler(struct clock_event_device *dev) 57 { 58 /* noting to do here */ 59 } 60 61 static irqreturn_t systick_interrupt(int irq, void *dev_id) 62 { 63 struct clock_event_device *dev = (struct clock_event_device *) dev_id; 64 65 dev->event_handler(dev); 66 67 return IRQ_HANDLED; 68 } 69 70 static struct systick_device systick = { 71 .dev = { 72 /* 73 * cevt-r4k uses 300, make sure systick 74 * gets used if available 75 */ 76 .rating = 310, 77 .features = CLOCK_EVT_FEAT_ONESHOT, 78 .set_next_event = systick_next_event, 79 .set_state_shutdown = systick_shutdown, 80 .set_state_oneshot = systick_set_oneshot, 81 .event_handler = systick_event_handler, 82 }, 83 }; 84 85 static struct irqaction systick_irqaction = { 86 .handler = systick_interrupt, 87 .flags = IRQF_PERCPU | IRQF_TIMER, 88 .dev_id = &systick.dev, 89 }; 90 91 static int systick_shutdown(struct clock_event_device *evt) 92 { 93 struct systick_device *sdev; 94 95 sdev = container_of(evt, struct systick_device, dev); 96 97 if (sdev->irq_requested) 98 free_irq(systick.dev.irq, &systick_irqaction); 99 sdev->irq_requested = 0; 100 iowrite32(0, systick.membase + SYSTICK_CONFIG); 101 102 return 0; 103 } 104 105 static int systick_set_oneshot(struct clock_event_device *evt) 106 { 107 struct systick_device *sdev; 108 109 sdev = container_of(evt, struct systick_device, dev); 110 111 if (!sdev->irq_requested) 112 setup_irq(systick.dev.irq, &systick_irqaction); 113 sdev->irq_requested = 1; 114 iowrite32(CFG_EXT_STK_EN | CFG_CNT_EN, 115 systick.membase + SYSTICK_CONFIG); 116 117 return 0; 118 } 119 120 static int __init ralink_systick_init(struct device_node *np) 121 { 122 int ret; 123 124 systick.membase = of_iomap(np, 0); 125 if (!systick.membase) 126 return -ENXIO; 127 128 systick_irqaction.name = np->name; 129 systick.dev.name = np->name; 130 clockevents_calc_mult_shift(&systick.dev, SYSTICK_FREQ, 60); 131 systick.dev.max_delta_ns = clockevent_delta2ns(0x7fff, &systick.dev); 132 systick.dev.max_delta_ticks = 0x7fff; 133 systick.dev.min_delta_ns = clockevent_delta2ns(0x3, &systick.dev); 134 systick.dev.min_delta_ticks = 0x3; 135 systick.dev.irq = irq_of_parse_and_map(np, 0); 136 if (!systick.dev.irq) { 137 pr_err("%s: request_irq failed", np->name); 138 return -EINVAL; 139 } 140 141 ret = clocksource_mmio_init(systick.membase + SYSTICK_COUNT, np->name, 142 SYSTICK_FREQ, 301, 16, 143 clocksource_mmio_readl_up); 144 if (ret) 145 return ret; 146 147 clockevents_register_device(&systick.dev); 148 149 pr_info("%s: running - mult: %d, shift: %d\n", 150 np->name, systick.dev.mult, systick.dev.shift); 151 152 return 0; 153 } 154 155 TIMER_OF_DECLARE(systick, "ralink,cevt-systick", ralink_systick_init); 156