1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * arch/arm/mach-vt8500/timer.c 4 * 5 * Copyright (C) 2012 Tony Prisk <linux@prisktech.co.nz> 6 * Copyright (C) 2010 Alexey Charkov <alchark@gmail.com> 7 */ 8 9 /* 10 * This file is copied and modified from the original timer.c provided by 11 * Alexey Charkov. Minor changes have been made for Device Tree Support. 12 */ 13 14 #include <linux/io.h> 15 #include <linux/irq.h> 16 #include <linux/interrupt.h> 17 #include <linux/clocksource.h> 18 #include <linux/clockchips.h> 19 #include <linux/delay.h> 20 21 #include <linux/of.h> 22 #include <linux/of_address.h> 23 #include <linux/of_irq.h> 24 25 #define VT8500_TIMER_OFFSET 0x0100 26 #define VT8500_TIMER_HZ 3000000 27 #define TIMER_MATCH_VAL 0x0000 28 #define TIMER_COUNT_VAL 0x0010 29 #define TIMER_STATUS_VAL 0x0014 30 #define TIMER_IER_VAL 0x001c /* interrupt enable */ 31 #define TIMER_CTRL_VAL 0x0020 32 #define TIMER_AS_VAL 0x0024 /* access status */ 33 #define TIMER_COUNT_R_ACTIVE (1 << 5) /* not ready for read */ 34 #define TIMER_COUNT_W_ACTIVE (1 << 4) /* not ready for write */ 35 #define TIMER_MATCH_W_ACTIVE (1 << 0) /* not ready for write */ 36 37 #define msecs_to_loops(t) (loops_per_jiffy / 1000 * HZ * t) 38 39 #define MIN_OSCR_DELTA 16 40 41 static void __iomem *regbase; 42 43 static u64 vt8500_timer_read(struct clocksource *cs) 44 { 45 int loops = msecs_to_loops(10); 46 writel(3, regbase + TIMER_CTRL_VAL); 47 while ((readl((regbase + TIMER_AS_VAL)) & TIMER_COUNT_R_ACTIVE) 48 && --loops) 49 cpu_relax(); 50 return readl(regbase + TIMER_COUNT_VAL); 51 } 52 53 static struct clocksource clocksource = { 54 .name = "vt8500_timer", 55 .rating = 200, 56 .read = vt8500_timer_read, 57 .mask = CLOCKSOURCE_MASK(32), 58 .flags = CLOCK_SOURCE_IS_CONTINUOUS, 59 }; 60 61 static int vt8500_timer_set_next_event(unsigned long cycles, 62 struct clock_event_device *evt) 63 { 64 int loops = msecs_to_loops(10); 65 u64 alarm = clocksource.read(&clocksource) + cycles; 66 while ((readl(regbase + TIMER_AS_VAL) & TIMER_MATCH_W_ACTIVE) 67 && --loops) 68 cpu_relax(); 69 writel((unsigned long)alarm, regbase + TIMER_MATCH_VAL); 70 71 if ((signed)(alarm - clocksource.read(&clocksource)) <= MIN_OSCR_DELTA) 72 return -ETIME; 73 74 writel(1, regbase + TIMER_IER_VAL); 75 76 return 0; 77 } 78 79 static int vt8500_shutdown(struct clock_event_device *evt) 80 { 81 writel(readl(regbase + TIMER_CTRL_VAL) | 1, regbase + TIMER_CTRL_VAL); 82 writel(0, regbase + TIMER_IER_VAL); 83 return 0; 84 } 85 86 static struct clock_event_device clockevent = { 87 .name = "vt8500_timer", 88 .features = CLOCK_EVT_FEAT_ONESHOT, 89 .rating = 200, 90 .set_next_event = vt8500_timer_set_next_event, 91 .set_state_shutdown = vt8500_shutdown, 92 .set_state_oneshot = vt8500_shutdown, 93 }; 94 95 static irqreturn_t vt8500_timer_interrupt(int irq, void *dev_id) 96 { 97 struct clock_event_device *evt = dev_id; 98 writel(0xf, regbase + TIMER_STATUS_VAL); 99 evt->event_handler(evt); 100 101 return IRQ_HANDLED; 102 } 103 104 static int __init vt8500_timer_init(struct device_node *np) 105 { 106 int timer_irq, ret; 107 108 regbase = of_iomap(np, 0); 109 if (!regbase) { 110 pr_err("%s: Missing iobase description in Device Tree\n", 111 __func__); 112 return -ENXIO; 113 } 114 115 timer_irq = irq_of_parse_and_map(np, 0); 116 if (!timer_irq) { 117 pr_err("%s: Missing irq description in Device Tree\n", 118 __func__); 119 return -EINVAL; 120 } 121 122 writel(1, regbase + TIMER_CTRL_VAL); 123 writel(0xf, regbase + TIMER_STATUS_VAL); 124 writel(~0, regbase + TIMER_MATCH_VAL); 125 126 ret = clocksource_register_hz(&clocksource, VT8500_TIMER_HZ); 127 if (ret) { 128 pr_err("%s: clocksource_register failed for %s\n", 129 __func__, clocksource.name); 130 return ret; 131 } 132 133 clockevent.cpumask = cpumask_of(0); 134 135 ret = request_irq(timer_irq, vt8500_timer_interrupt, 136 IRQF_TIMER | IRQF_IRQPOLL, "vt8500_timer", 137 &clockevent); 138 if (ret) { 139 pr_err("%s: setup_irq failed for %s\n", __func__, 140 clockevent.name); 141 return ret; 142 } 143 144 clockevents_config_and_register(&clockevent, VT8500_TIMER_HZ, 145 MIN_OSCR_DELTA * 2, 0xf0000000); 146 147 return 0; 148 } 149 150 TIMER_OF_DECLARE(vt8500, "via,vt8500-timer", vt8500_timer_init); 151