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