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/time.h> 17 #include <linux/clocksource.h> 18 #include <linux/interrupt.h> 19 #include <linux/module.h> 20 #include <linux/init.h> 21 #include <linux/irq.h> 22 #include <linux/profile.h> 23 #include <linux/delay.h> 24 25 #include <asm/timex.h> 26 #include <asm/platform.h> 27 28 #ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT 29 unsigned long ccount_per_jiffy; /* per 1/HZ */ 30 unsigned long nsec_per_ccount; /* nsec per ccount increment */ 31 #endif 32 33 static cycle_t ccount_read(void) 34 { 35 return (cycle_t)get_ccount(); 36 } 37 38 static struct clocksource ccount_clocksource = { 39 .name = "ccount", 40 .rating = 200, 41 .read = ccount_read, 42 .mask = CLOCKSOURCE_MASK(32), 43 /* 44 * With a shift of 22 the lower limit of the cpu clock is 45 * 1MHz, where NSEC_PER_CCOUNT is 1000 or a bit less than 46 * 2^10: Since we have 32 bits and the multiplicator can 47 * already take up as much as 10 bits, this leaves us with 48 * remaining upper 22 bits. 49 */ 50 .shift = 22, 51 }; 52 53 static irqreturn_t timer_interrupt(int irq, void *dev_id); 54 static struct irqaction timer_irqaction = { 55 .handler = timer_interrupt, 56 .flags = IRQF_DISABLED, 57 .name = "timer", 58 }; 59 60 void __init time_init(void) 61 { 62 xtime.tv_nsec = 0; 63 xtime.tv_sec = read_persistent_clock(); 64 65 set_normalized_timespec(&wall_to_monotonic, 66 -xtime.tv_sec, -xtime.tv_nsec); 67 68 #ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT 69 printk("Calibrating CPU frequency "); 70 platform_calibrate_ccount(); 71 printk("%d.%02d MHz\n", (int)ccount_per_jiffy/(1000000/HZ), 72 (int)(ccount_per_jiffy/(10000/HZ))%100); 73 #endif 74 ccount_clocksource.mult = 75 clocksource_hz2mult(CCOUNT_PER_JIFFY * HZ, 76 ccount_clocksource.shift); 77 clocksource_register(&ccount_clocksource); 78 79 /* Initialize the linux timer interrupt. */ 80 81 setup_irq(LINUX_TIMER_INT, &timer_irqaction); 82 set_linux_timer(get_ccount() + CCOUNT_PER_JIFFY); 83 } 84 85 /* 86 * The timer interrupt is called HZ times per second. 87 */ 88 89 irqreturn_t timer_interrupt (int irq, void *dev_id) 90 { 91 92 unsigned long next; 93 94 next = get_linux_timer(); 95 96 again: 97 while ((signed long)(get_ccount() - next) > 0) { 98 99 profile_tick(CPU_PROFILING); 100 #ifndef CONFIG_SMP 101 update_process_times(user_mode(get_irq_regs())); 102 #endif 103 104 write_seqlock(&xtime_lock); 105 106 do_timer(1); /* Linux handler in kernel/timer.c */ 107 108 /* Note that writing CCOMPARE clears the interrupt. */ 109 110 next += CCOUNT_PER_JIFFY; 111 set_linux_timer(next); 112 113 write_sequnlock(&xtime_lock); 114 } 115 116 /* Allow platform to do something useful (Wdog). */ 117 118 platform_heartbeat(); 119 120 /* Make sure we didn't miss any tick... */ 121 122 if ((signed long)(get_ccount() - next) > 0) 123 goto again; 124 125 return IRQ_HANDLED; 126 } 127 128 #ifndef CONFIG_GENERIC_CALIBRATE_DELAY 129 void __cpuinit calibrate_delay(void) 130 { 131 loops_per_jiffy = CCOUNT_PER_JIFFY; 132 printk("Calibrating delay loop (skipped)... " 133 "%lu.%02lu BogoMIPS preset\n", 134 loops_per_jiffy/(1000000/HZ), 135 (loops_per_jiffy/(10000/HZ)) % 100); 136 } 137 #endif 138