1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * linux/arch/arm/common/time-acorn.c 4 * 5 * Copyright (c) 1996-2000 Russell King. 6 * 7 * Changelog: 8 * 24-Sep-1996 RMK Created 9 * 10-Oct-1996 RMK Brought up to date with arch-sa110eval 10 * 04-Dec-1997 RMK Updated for new arch/arm/time.c 11 * 13=Jun-2004 DS Moved to arch/arm/common b/c shared w/CLPS7500 12 */ 13 #include <linux/clocksource.h> 14 #include <linux/init.h> 15 #include <linux/interrupt.h> 16 #include <linux/irq.h> 17 #include <linux/io.h> 18 19 #include <mach/hardware.h> 20 #include <asm/hardware/ioc.h> 21 22 #include <asm/mach/time.h> 23 24 #define RPC_CLOCK_FREQ 2000000 25 #define RPC_LATCH DIV_ROUND_CLOSEST(RPC_CLOCK_FREQ, HZ) 26 27 static u32 ioc_time; 28 29 static u64 ioc_timer_read(struct clocksource *cs) 30 { 31 unsigned int count1, count2, status; 32 unsigned long flags; 33 u32 ticks; 34 35 local_irq_save(flags); 36 ioc_writeb (0, IOC_T0LATCH); 37 barrier (); 38 count1 = ioc_readb(IOC_T0CNTL) | (ioc_readb(IOC_T0CNTH) << 8); 39 barrier (); 40 status = ioc_readb(IOC_IRQREQA); 41 barrier (); 42 ioc_writeb (0, IOC_T0LATCH); 43 barrier (); 44 count2 = ioc_readb(IOC_T0CNTL) | (ioc_readb(IOC_T0CNTH) << 8); 45 ticks = ioc_time + RPC_LATCH - count2; 46 local_irq_restore(flags); 47 48 if (count2 < count1) { 49 /* 50 * The timer has not reloaded between reading count1 and 51 * count2, check whether an interrupt was actually pending. 52 */ 53 if (status & (1 << 5)) 54 ticks += RPC_LATCH; 55 } else if (count2 > count1) { 56 /* 57 * The timer has reloaded, so count2 indicates the new 58 * count since the wrap. The interrupt would not have 59 * been processed, so add the missed ticks. 60 */ 61 ticks += RPC_LATCH; 62 } 63 64 return ticks; 65 } 66 67 static struct clocksource ioctime_clocksource = { 68 .read = ioc_timer_read, 69 .mask = CLOCKSOURCE_MASK(32), 70 .rating = 100, 71 }; 72 73 void __init ioctime_init(void) 74 { 75 ioc_writeb(RPC_LATCH & 255, IOC_T0LTCHL); 76 ioc_writeb(RPC_LATCH >> 8, IOC_T0LTCHH); 77 ioc_writeb(0, IOC_T0GO); 78 } 79 80 static irqreturn_t 81 ioc_timer_interrupt(int irq, void *dev_id) 82 { 83 ioc_time += RPC_LATCH; 84 timer_tick(); 85 return IRQ_HANDLED; 86 } 87 88 static struct irqaction ioc_timer_irq = { 89 .name = "timer", 90 .handler = ioc_timer_interrupt 91 }; 92 93 /* 94 * Set up timer interrupt. 95 */ 96 void __init ioc_timer_init(void) 97 { 98 WARN_ON(clocksource_register_hz(&ioctime_clocksource, RPC_CLOCK_FREQ)); 99 ioctime_init(); 100 setup_irq(IRQ_TIMER0, &ioc_timer_irq); 101 } 102