1 /* 2 * arch/xtensa/kernel/time.c 3 * 4 * Timer and clock support. 5 * 6 * This file is subject to the terms and conditions of the GNU General Public 7 * License. See the file "COPYING" in the main directory of this archive 8 * for more details. 9 * 10 * Copyright (C) 2005 Tensilica Inc. 11 * 12 * Chris Zankel <chris@zankel.net> 13 */ 14 15 #include <linux/errno.h> 16 #include <linux/sched.h> 17 #include <linux/time.h> 18 #include <linux/clocksource.h> 19 #include <linux/interrupt.h> 20 #include <linux/module.h> 21 #include <linux/init.h> 22 #include <linux/irq.h> 23 #include <linux/profile.h> 24 #include <linux/delay.h> 25 26 #include <asm/timex.h> 27 #include <asm/platform.h> 28 29 #ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT 30 unsigned long ccount_per_jiffy; /* per 1/HZ */ 31 unsigned long nsec_per_ccount; /* nsec per ccount increment */ 32 #endif 33 34 static cycle_t ccount_read(void) 35 { 36 return (cycle_t)get_ccount(); 37 } 38 39 static struct clocksource ccount_clocksource = { 40 .name = "ccount", 41 .rating = 200, 42 .read = ccount_read, 43 .mask = CLOCKSOURCE_MASK(32), 44 /* 45 * With a shift of 22 the lower limit of the cpu clock is 46 * 1MHz, where NSEC_PER_CCOUNT is 1000 or a bit less than 47 * 2^10: Since we have 32 bits and the multiplicator can 48 * already take up as much as 10 bits, this leaves us with 49 * remaining upper 22 bits. 50 */ 51 .shift = 22, 52 }; 53 54 static irqreturn_t timer_interrupt(int irq, void *dev_id); 55 static struct irqaction timer_irqaction = { 56 .handler = timer_interrupt, 57 .flags = IRQF_DISABLED, 58 .name = "timer", 59 }; 60 61 void __init time_init(void) 62 { 63 #ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT 64 printk("Calibrating CPU frequency "); 65 platform_calibrate_ccount(); 66 printk("%d.%02d MHz\n", (int)ccount_per_jiffy/(1000000/HZ), 67 (int)(ccount_per_jiffy/(10000/HZ))%100); 68 #endif 69 ccount_clocksource.mult = 70 clocksource_hz2mult(CCOUNT_PER_JIFFY * HZ, 71 ccount_clocksource.shift); 72 clocksource_register(&ccount_clocksource); 73 74 /* Initialize the linux timer interrupt. */ 75 76 setup_irq(LINUX_TIMER_INT, &timer_irqaction); 77 set_linux_timer(get_ccount() + CCOUNT_PER_JIFFY); 78 } 79 80 /* 81 * The timer interrupt is called HZ times per second. 82 */ 83 84 irqreturn_t timer_interrupt (int irq, void *dev_id) 85 { 86 87 unsigned long next; 88 89 next = get_linux_timer(); 90 91 again: 92 while ((signed long)(get_ccount() - next) > 0) { 93 94 profile_tick(CPU_PROFILING); 95 #ifndef CONFIG_SMP 96 update_process_times(user_mode(get_irq_regs())); 97 #endif 98 99 write_seqlock(&xtime_lock); 100 101 do_timer(1); /* Linux handler in kernel/timer.c */ 102 103 /* Note that writing CCOMPARE clears the interrupt. */ 104 105 next += CCOUNT_PER_JIFFY; 106 set_linux_timer(next); 107 108 write_sequnlock(&xtime_lock); 109 } 110 111 /* Allow platform to do something useful (Wdog). */ 112 113 platform_heartbeat(); 114 115 /* Make sure we didn't miss any tick... */ 116 117 if ((signed long)(get_ccount() - next) > 0) 118 goto again; 119 120 return IRQ_HANDLED; 121 } 122 123 #ifndef CONFIG_GENERIC_CALIBRATE_DELAY 124 void __cpuinit calibrate_delay(void) 125 { 126 loops_per_jiffy = CCOUNT_PER_JIFFY; 127 printk("Calibrating delay loop (skipped)... " 128 "%lu.%02lu BogoMIPS preset\n", 129 loops_per_jiffy/(1000000/HZ), 130 (loops_per_jiffy/(10000/HZ)) % 100); 131 } 132 #endif 133