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 int systick_shutdown(struct clock_event_device *evt) 86 { 87 struct systick_device *sdev; 88 89 sdev = container_of(evt, struct systick_device, dev); 90 91 if (sdev->irq_requested) 92 free_irq(systick.dev.irq, &systick.dev); 93 sdev->irq_requested = 0; 94 iowrite32(0, systick.membase + SYSTICK_CONFIG); 95 96 return 0; 97 } 98 99 static int systick_set_oneshot(struct clock_event_device *evt) 100 { 101 const char *name = systick.dev.name; 102 struct systick_device *sdev; 103 int irq = systick.dev.irq; 104 105 sdev = container_of(evt, struct systick_device, dev); 106 107 if (!sdev->irq_requested) { 108 if (request_irq(irq, systick_interrupt, 109 IRQF_PERCPU | IRQF_TIMER, name, &systick.dev)) 110 pr_err("Failed to request irq %d (%s)\n", irq, name); 111 } 112 sdev->irq_requested = 1; 113 iowrite32(CFG_EXT_STK_EN | CFG_CNT_EN, 114 systick.membase + SYSTICK_CONFIG); 115 116 return 0; 117 } 118 119 static int __init ralink_systick_init(struct device_node *np) 120 { 121 int ret; 122 123 systick.membase = of_iomap(np, 0); 124 if (!systick.membase) 125 return -ENXIO; 126 127 systick.dev.name = np->name; 128 clockevents_calc_mult_shift(&systick.dev, SYSTICK_FREQ, 60); 129 systick.dev.max_delta_ns = clockevent_delta2ns(0x7fff, &systick.dev); 130 systick.dev.max_delta_ticks = 0x7fff; 131 systick.dev.min_delta_ns = clockevent_delta2ns(0x3, &systick.dev); 132 systick.dev.min_delta_ticks = 0x3; 133 systick.dev.irq = irq_of_parse_and_map(np, 0); 134 if (!systick.dev.irq) { 135 pr_err("%pOFn: request_irq failed", np); 136 return -EINVAL; 137 } 138 139 ret = clocksource_mmio_init(systick.membase + SYSTICK_COUNT, np->name, 140 SYSTICK_FREQ, 301, 16, 141 clocksource_mmio_readl_up); 142 if (ret) 143 return ret; 144 145 clockevents_register_device(&systick.dev); 146 147 pr_info("%pOFn: running - mult: %d, shift: %d\n", 148 np, systick.dev.mult, systick.dev.shift); 149 150 return 0; 151 } 152 153 TIMER_OF_DECLARE(systick, "ralink,cevt-systick", ralink_systick_init); 154