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 #define RPC_CLOCK_FREQ 2000000 28 #define RPC_LATCH DIV_ROUND_CLOSEST(RPC_CLOCK_FREQ, HZ) 29 30 static u32 ioc_timer_gettimeoffset(void) 31 { 32 unsigned int count1, count2, status; 33 long offset; 34 35 ioc_writeb (0, IOC_T0LATCH); 36 barrier (); 37 count1 = ioc_readb(IOC_T0CNTL) | (ioc_readb(IOC_T0CNTH) << 8); 38 barrier (); 39 status = ioc_readb(IOC_IRQREQA); 40 barrier (); 41 ioc_writeb (0, IOC_T0LATCH); 42 barrier (); 43 count2 = ioc_readb(IOC_T0CNTL) | (ioc_readb(IOC_T0CNTH) << 8); 44 45 offset = count2; 46 if (count2 < count1) { 47 /* 48 * We have not had an interrupt between reading count1 49 * and count2. 50 */ 51 if (status & (1 << 5)) 52 offset -= RPC_LATCH; 53 } else if (count2 > count1) { 54 /* 55 * We have just had another interrupt between reading 56 * count1 and count2. 57 */ 58 offset -= RPC_LATCH; 59 } 60 61 offset = (RPC_LATCH - offset) * (tick_nsec / 1000); 62 return DIV_ROUND_CLOSEST(offset, RPC_LATCH) * 1000; 63 } 64 65 void __init ioctime_init(void) 66 { 67 ioc_writeb(RPC_LATCH & 255, IOC_T0LTCHL); 68 ioc_writeb(RPC_LATCH >> 8, IOC_T0LTCHH); 69 ioc_writeb(0, IOC_T0GO); 70 } 71 72 static irqreturn_t 73 ioc_timer_interrupt(int irq, void *dev_id) 74 { 75 timer_tick(); 76 return IRQ_HANDLED; 77 } 78 79 static struct irqaction ioc_timer_irq = { 80 .name = "timer", 81 .handler = ioc_timer_interrupt 82 }; 83 84 /* 85 * Set up timer interrupt. 86 */ 87 void __init ioc_timer_init(void) 88 { 89 arch_gettimeoffset = ioc_timer_gettimeoffset; 90 ioctime_init(); 91 setup_irq(IRQ_TIMER0, &ioc_timer_irq); 92 } 93