1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * OpenRISC time.c 4 * 5 * Linux architectural port borrowing liberally from similar works of 6 * others. All original copyrights apply as per the original source 7 * declaration. 8 * 9 * Modifications for the OpenRISC architecture: 10 * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se> 11 */ 12 13 #include <linux/kernel.h> 14 #include <linux/time.h> 15 #include <linux/timex.h> 16 #include <linux/interrupt.h> 17 #include <linux/ftrace.h> 18 19 #include <linux/clocksource.h> 20 #include <linux/clockchips.h> 21 #include <linux/irq.h> 22 #include <linux/io.h> 23 24 #include <asm/cpuinfo.h> 25 26 /* Test the timer ticks to count, used in sync routine */ 27 inline void openrisc_timer_set(unsigned long count) 28 { 29 mtspr(SPR_TTCR, count); 30 } 31 32 /* Set the timer to trigger in delta cycles */ 33 inline void openrisc_timer_set_next(unsigned long delta) 34 { 35 u32 c; 36 37 /* Read 32-bit counter value, add delta, mask off the low 28 bits. 38 * We're guaranteed delta won't be bigger than 28 bits because the 39 * generic timekeeping code ensures that for us. 40 */ 41 c = mfspr(SPR_TTCR); 42 c += delta; 43 c &= SPR_TTMR_TP; 44 45 /* Set counter and enable interrupt. 46 * Keep timer in continuous mode always. 47 */ 48 mtspr(SPR_TTMR, SPR_TTMR_CR | SPR_TTMR_IE | c); 49 } 50 51 static int openrisc_timer_set_next_event(unsigned long delta, 52 struct clock_event_device *dev) 53 { 54 openrisc_timer_set_next(delta); 55 return 0; 56 } 57 58 /* This is the clock event device based on the OR1K tick timer. 59 * As the timer is being used as a continuous clock-source (required for HR 60 * timers) we cannot enable the PERIODIC feature. The tick timer can run using 61 * one-shot events, so no problem. 62 */ 63 DEFINE_PER_CPU(struct clock_event_device, clockevent_openrisc_timer); 64 65 void openrisc_clockevent_init(void) 66 { 67 unsigned int cpu = smp_processor_id(); 68 struct clock_event_device *evt = 69 &per_cpu(clockevent_openrisc_timer, cpu); 70 struct cpuinfo_or1k *cpuinfo = &cpuinfo_or1k[cpu]; 71 72 mtspr(SPR_TTMR, SPR_TTMR_CR); 73 74 #ifdef CONFIG_SMP 75 evt->broadcast = tick_broadcast; 76 #endif 77 evt->name = "openrisc_timer_clockevent", 78 evt->features = CLOCK_EVT_FEAT_ONESHOT, 79 evt->rating = 300, 80 evt->set_next_event = openrisc_timer_set_next_event, 81 82 evt->cpumask = cpumask_of(cpu); 83 84 /* We only have 28 bits */ 85 clockevents_config_and_register(evt, cpuinfo->clock_frequency, 86 100, 0x0fffffff); 87 88 } 89 90 static inline void timer_ack(void) 91 { 92 /* Clear the IP bit and disable further interrupts */ 93 /* This can be done very simply... we just need to keep the timer 94 running, so just maintain the CR bits while clearing the rest 95 of the register 96 */ 97 mtspr(SPR_TTMR, SPR_TTMR_CR); 98 } 99 100 /* 101 * The timer interrupt is mostly handled in generic code nowadays... this 102 * function just acknowledges the interrupt and fires the event handler that 103 * has been set on the clockevent device by the generic time management code. 104 * 105 * This function needs to be called by the timer exception handler and that's 106 * all the exception handler needs to do. 107 */ 108 109 irqreturn_t __irq_entry timer_interrupt(struct pt_regs *regs) 110 { 111 struct pt_regs *old_regs = set_irq_regs(regs); 112 unsigned int cpu = smp_processor_id(); 113 struct clock_event_device *evt = 114 &per_cpu(clockevent_openrisc_timer, cpu); 115 116 timer_ack(); 117 118 /* 119 * update_process_times() expects us to have called irq_enter(). 120 */ 121 irq_enter(); 122 evt->event_handler(evt); 123 irq_exit(); 124 125 set_irq_regs(old_regs); 126 127 return IRQ_HANDLED; 128 } 129 130 /* 131 * Clocksource: Based on OpenRISC timer/counter 132 * 133 * This sets up the OpenRISC Tick Timer as a clock source. The tick timer 134 * is 32 bits wide and runs at the CPU clock frequency. 135 */ 136 static u64 openrisc_timer_read(struct clocksource *cs) 137 { 138 return (u64) mfspr(SPR_TTCR); 139 } 140 141 static struct clocksource openrisc_timer = { 142 .name = "openrisc_timer", 143 .rating = 200, 144 .read = openrisc_timer_read, 145 .mask = CLOCKSOURCE_MASK(32), 146 .flags = CLOCK_SOURCE_IS_CONTINUOUS, 147 }; 148 149 static int __init openrisc_timer_init(void) 150 { 151 struct cpuinfo_or1k *cpuinfo = &cpuinfo_or1k[smp_processor_id()]; 152 153 if (clocksource_register_hz(&openrisc_timer, cpuinfo->clock_frequency)) 154 panic("failed to register clocksource"); 155 156 /* Enable the incrementer: 'continuous' mode with interrupt disabled */ 157 mtspr(SPR_TTMR, SPR_TTMR_CR); 158 159 return 0; 160 } 161 162 void __init time_init(void) 163 { 164 u32 upr; 165 166 upr = mfspr(SPR_UPR); 167 if (!(upr & SPR_UPR_TTP)) 168 panic("Linux not supported on devices without tick timer"); 169 170 openrisc_timer_init(); 171 openrisc_clockevent_init(); 172 } 173