98 строки
2.3 KiB
C
98 строки
2.3 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* linux/arch/arm/common/time-acorn.c
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*
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* Copyright (c) 1996-2000 Russell King.
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*
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* Changelog:
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* 24-Sep-1996 RMK Created
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* 10-Oct-1996 RMK Brought up to date with arch-sa110eval
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* 04-Dec-1997 RMK Updated for new arch/arm/time.c
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* 13=Jun-2004 DS Moved to arch/arm/common b/c shared w/CLPS7500
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*/
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#include <linux/clocksource.h>
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#include <linux/init.h>
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#include <linux/interrupt.h>
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#include <linux/irq.h>
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#include <linux/io.h>
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#include <mach/hardware.h>
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#include <asm/hardware/ioc.h>
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#include <asm/mach/time.h>
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#define RPC_CLOCK_FREQ 2000000
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#define RPC_LATCH DIV_ROUND_CLOSEST(RPC_CLOCK_FREQ, HZ)
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static u32 ioc_time;
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static u64 ioc_timer_read(struct clocksource *cs)
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{
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unsigned int count1, count2, status;
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unsigned long flags;
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u32 ticks;
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local_irq_save(flags);
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ioc_writeb (0, IOC_T0LATCH);
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barrier ();
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count1 = ioc_readb(IOC_T0CNTL) | (ioc_readb(IOC_T0CNTH) << 8);
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barrier ();
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status = ioc_readb(IOC_IRQREQA);
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barrier ();
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ioc_writeb (0, IOC_T0LATCH);
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barrier ();
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count2 = ioc_readb(IOC_T0CNTL) | (ioc_readb(IOC_T0CNTH) << 8);
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ticks = ioc_time + RPC_LATCH - count2;
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local_irq_restore(flags);
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if (count2 < count1) {
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/*
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* The timer has not reloaded between reading count1 and
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* count2, check whether an interrupt was actually pending.
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*/
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if (status & (1 << 5))
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ticks += RPC_LATCH;
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} else if (count2 > count1) {
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/*
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* The timer has reloaded, so count2 indicates the new
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* count since the wrap. The interrupt would not have
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* been processed, so add the missed ticks.
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*/
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ticks += RPC_LATCH;
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}
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return ticks;
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}
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static struct clocksource ioctime_clocksource = {
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.read = ioc_timer_read,
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.mask = CLOCKSOURCE_MASK(32),
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.rating = 100,
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};
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void __init ioctime_init(void)
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{
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ioc_writeb(RPC_LATCH & 255, IOC_T0LTCHL);
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ioc_writeb(RPC_LATCH >> 8, IOC_T0LTCHH);
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ioc_writeb(0, IOC_T0GO);
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}
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static irqreturn_t
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ioc_timer_interrupt(int irq, void *dev_id)
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{
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ioc_time += RPC_LATCH;
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legacy_timer_tick(1);
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return IRQ_HANDLED;
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}
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/*
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* Set up timer interrupt.
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*/
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void __init ioc_timer_init(void)
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{
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WARN_ON(clocksource_register_hz(&ioctime_clocksource, RPC_CLOCK_FREQ));
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ioctime_init();
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if (request_irq(IRQ_TIMER0, ioc_timer_interrupt, 0, "timer", NULL))
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pr_err("Failed to request irq %d (timer)\n", IRQ_TIMER0);
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}
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