1 /* 2 * Copyright 2001 MontaVista Software Inc. 3 * Author: Jun Sun, jsun@mvista.com or jsun@junsun.net 4 * Copyright (c) 2003, 2004 Maciej W. Rozycki 5 * 6 * Common time service routines for MIPS machines. 7 * 8 * This program is free software; you can redistribute it and/or modify it 9 * under the terms of the GNU General Public License as published by the 10 * Free Software Foundation; either version 2 of the License, or (at your 11 * option) any later version. 12 */ 13 #include <linux/bug.h> 14 #include <linux/clockchips.h> 15 #include <linux/types.h> 16 #include <linux/kernel.h> 17 #include <linux/init.h> 18 #include <linux/sched.h> 19 #include <linux/param.h> 20 #include <linux/time.h> 21 #include <linux/timex.h> 22 #include <linux/smp.h> 23 #include <linux/spinlock.h> 24 #include <linux/export.h> 25 26 #include <asm/cpu-features.h> 27 #include <asm/cpu-type.h> 28 #include <asm/div64.h> 29 #include <asm/time.h> 30 31 /* 32 * forward reference 33 */ 34 DEFINE_SPINLOCK(rtc_lock); 35 EXPORT_SYMBOL(rtc_lock); 36 37 static int null_perf_irq(void) 38 { 39 return 0; 40 } 41 42 int (*perf_irq)(void) = null_perf_irq; 43 44 EXPORT_SYMBOL(perf_irq); 45 46 /* 47 * time_init() - it does the following things. 48 * 49 * 1) plat_time_init() - 50 * a) (optional) set up RTC routines, 51 * b) (optional) calibrate and set the mips_hpt_frequency 52 * (only needed if you intended to use cpu counter as timer interrupt 53 * source) 54 * 2) calculate a couple of cached variables for later usage 55 */ 56 57 unsigned int mips_hpt_frequency; 58 EXPORT_SYMBOL_GPL(mips_hpt_frequency); 59 60 static __init int cpu_has_mfc0_count_bug(void) 61 { 62 switch (current_cpu_type()) { 63 case CPU_R4000PC: 64 case CPU_R4000SC: 65 case CPU_R4000MC: 66 /* 67 * V3.0 is documented as suffering from the mfc0 from count bug. 68 * Afaik this is the last version of the R4000. Later versions 69 * were marketed as R4400. 70 */ 71 return 1; 72 73 case CPU_R4400PC: 74 case CPU_R4400SC: 75 case CPU_R4400MC: 76 /* 77 * The published errata for the R4400 up to 3.0 say the CPU 78 * has the mfc0 from count bug. 79 */ 80 if ((current_cpu_data.processor_id & 0xff) <= 0x30) 81 return 1; 82 83 /* 84 * we assume newer revisions are ok 85 */ 86 return 0; 87 } 88 89 return 0; 90 } 91 92 void __init time_init(void) 93 { 94 plat_time_init(); 95 96 /* 97 * The use of the R4k timer as a clock event takes precedence; 98 * if reading the Count register might interfere with the timer 99 * interrupt, then we don't use the timer as a clock source. 100 * We may still use the timer as a clock source though if the 101 * timer interrupt isn't reliable; the interference doesn't 102 * matter then, because we don't use the interrupt. 103 */ 104 if (mips_clockevent_init() != 0 || !cpu_has_mfc0_count_bug()) 105 init_mips_clocksource(); 106 } 107