1 /* 2 * linux/arch/arm/common/time-acorn.c 3 * 4 * Copyright (c) 1996-2000 Russell King. 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License version 2 as 8 * published by the Free Software Foundation. 9 * 10 * Changelog: 11 * 24-Sep-1996 RMK Created 12 * 10-Oct-1996 RMK Brought up to date with arch-sa110eval 13 * 04-Dec-1997 RMK Updated for new arch/arm/time.c 14 * 13=Jun-2004 DS Moved to arch/arm/common b/c shared w/CLPS7500 15 */ 16 #include <linux/timex.h> 17 #include <linux/init.h> 18 #include <linux/interrupt.h> 19 #include <linux/irq.h> 20 #include <linux/io.h> 21 22 #include <mach/hardware.h> 23 #include <asm/hardware/ioc.h> 24 25 #include <asm/mach/time.h> 26 27 static u32 ioc_timer_gettimeoffset(void) 28 { 29 unsigned int count1, count2, status; 30 long offset; 31 32 ioc_writeb (0, IOC_T0LATCH); 33 barrier (); 34 count1 = ioc_readb(IOC_T0CNTL) | (ioc_readb(IOC_T0CNTH) << 8); 35 barrier (); 36 status = ioc_readb(IOC_IRQREQA); 37 barrier (); 38 ioc_writeb (0, IOC_T0LATCH); 39 barrier (); 40 count2 = ioc_readb(IOC_T0CNTL) | (ioc_readb(IOC_T0CNTH) << 8); 41 42 offset = count2; 43 if (count2 < count1) { 44 /* 45 * We have not had an interrupt between reading count1 46 * and count2. 47 */ 48 if (status & (1 << 5)) 49 offset -= LATCH; 50 } else if (count2 > count1) { 51 /* 52 * We have just had another interrupt between reading 53 * count1 and count2. 54 */ 55 offset -= LATCH; 56 } 57 58 offset = (LATCH - offset) * (tick_nsec / 1000); 59 return ((offset + LATCH/2) / LATCH) * 1000; 60 } 61 62 void __init ioctime_init(void) 63 { 64 ioc_writeb(LATCH & 255, IOC_T0LTCHL); 65 ioc_writeb(LATCH >> 8, IOC_T0LTCHH); 66 ioc_writeb(0, IOC_T0GO); 67 } 68 69 static irqreturn_t 70 ioc_timer_interrupt(int irq, void *dev_id) 71 { 72 timer_tick(); 73 return IRQ_HANDLED; 74 } 75 76 static struct irqaction ioc_timer_irq = { 77 .name = "timer", 78 .flags = IRQF_DISABLED, 79 .handler = ioc_timer_interrupt 80 }; 81 82 /* 83 * Set up timer interrupt. 84 */ 85 void __init ioc_timer_init(void) 86 { 87 arch_gettimeoffset = ioc_timer_gettimeoffset; 88 ioctime_init(); 89 setup_irq(IRQ_TIMER0, &ioc_timer_irq); 90 } 91