258 lines
6.5 KiB
C
258 lines
6.5 KiB
C
/* linux/arch/arm/mach-s3c2410/time.c
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*
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* Copyright (C) 2003-2005 Simtec Electronics
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* Ben Dooks, <ben@simtec.co.uk>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include <linux/config.h>
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#include <linux/kernel.h>
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#include <linux/sched.h>
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#include <linux/init.h>
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#include <linux/interrupt.h>
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#include <linux/err.h>
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#include <asm/system.h>
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#include <asm/leds.h>
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#include <asm/mach-types.h>
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#include <asm/io.h>
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#include <asm/irq.h>
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#include <asm/arch/map.h>
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#include <asm/arch/regs-timer.h>
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#include <asm/arch/regs-irq.h>
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#include <asm/mach/time.h>
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#include <asm/hardware/clock.h>
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#include "clock.h"
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#include "cpu.h"
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static unsigned long timer_startval;
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static unsigned long timer_usec_ticks;
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#define TIMER_USEC_SHIFT 16
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/* we use the shifted arithmetic to work out the ratio of timer ticks
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* to usecs, as often the peripheral clock is not a nice even multiple
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* of 1MHz.
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*
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* shift of 14 and 15 are too low for the 12MHz, 16 seems to be ok
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* for the current HZ value of 200 without producing overflows.
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*
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* Original patch by Dimitry Andric, updated by Ben Dooks
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*/
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/* timer_mask_usec_ticks
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*
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* given a clock and divisor, make the value to pass into timer_ticks_to_usec
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* to scale the ticks into usecs
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*/
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static inline unsigned long
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timer_mask_usec_ticks(unsigned long scaler, unsigned long pclk)
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{
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unsigned long den = pclk / 1000;
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return ((1000 << TIMER_USEC_SHIFT) * scaler + (den >> 1)) / den;
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}
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/* timer_ticks_to_usec
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*
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* convert timer ticks to usec.
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*/
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static inline unsigned long timer_ticks_to_usec(unsigned long ticks)
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{
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unsigned long res;
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res = ticks * timer_usec_ticks;
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res += 1 << (TIMER_USEC_SHIFT - 4); /* round up slightly */
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return res >> TIMER_USEC_SHIFT;
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}
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/***
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* Returns microsecond since last clock interrupt. Note that interrupts
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* will have been disabled by do_gettimeoffset()
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* IRQs are disabled before entering here from do_gettimeofday()
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*/
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#define SRCPND_TIMER4 (1<<(IRQ_TIMER4 - IRQ_EINT0))
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static unsigned long s3c2410_gettimeoffset (void)
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{
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unsigned long tdone;
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unsigned long irqpend;
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unsigned long tval;
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/* work out how many ticks have gone since last timer interrupt */
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tval = __raw_readl(S3C2410_TCNTO(4));
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tdone = timer_startval - tval;
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/* check to see if there is an interrupt pending */
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irqpend = __raw_readl(S3C2410_SRCPND);
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if (irqpend & SRCPND_TIMER4) {
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/* re-read the timer, and try and fix up for the missed
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* interrupt. Note, the interrupt may go off before the
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* timer has re-loaded from wrapping.
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*/
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tval = __raw_readl(S3C2410_TCNTO(4));
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tdone = timer_startval - tval;
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if (tval != 0)
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tdone += timer_startval;
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}
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return timer_ticks_to_usec(tdone);
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}
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/*
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* IRQ handler for the timer
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*/
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static irqreturn_t
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s3c2410_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
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{
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write_seqlock(&xtime_lock);
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timer_tick(regs);
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write_sequnlock(&xtime_lock);
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return IRQ_HANDLED;
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}
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static struct irqaction s3c2410_timer_irq = {
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.name = "S3C2410 Timer Tick",
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.flags = SA_INTERRUPT | SA_TIMER,
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.handler = s3c2410_timer_interrupt,
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};
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/*
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* Set up timer interrupt, and return the current time in seconds.
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*
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* Currently we only use timer4, as it is the only timer which has no
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* other function that can be exploited externally
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*/
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static void s3c2410_timer_setup (void)
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{
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unsigned long tcon;
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unsigned long tcnt;
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unsigned long tcfg1;
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unsigned long tcfg0;
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tcnt = 0xffff; /* default value for tcnt */
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/* read the current timer configuration bits */
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tcon = __raw_readl(S3C2410_TCON);
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tcfg1 = __raw_readl(S3C2410_TCFG1);
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tcfg0 = __raw_readl(S3C2410_TCFG0);
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/* configure the system for whichever machine is in use */
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if (machine_is_bast() || machine_is_vr1000() || machine_is_anubis()) {
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/* timer is at 12MHz, scaler is 1 */
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timer_usec_ticks = timer_mask_usec_ticks(1, 12000000);
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tcnt = 12000000 / HZ;
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tcfg1 &= ~S3C2410_TCFG1_MUX4_MASK;
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tcfg1 |= S3C2410_TCFG1_MUX4_TCLK1;
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} else {
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unsigned long pclk;
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struct clk *clk;
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/* for the h1940 (and others), we use the pclk from the core
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* to generate the timer values. since values around 50 to
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* 70MHz are not values we can directly generate the timer
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* value from, we need to pre-scale and divide before using it.
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*
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* for instance, using 50.7MHz and dividing by 6 gives 8.45MHz
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* (8.45 ticks per usec)
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*/
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/* this is used as default if no other timer can be found */
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clk = clk_get(NULL, "timers");
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if (IS_ERR(clk))
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panic("failed to get clock for system timer");
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clk_use(clk);
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clk_enable(clk);
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pclk = clk_get_rate(clk);
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/* configure clock tick */
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timer_usec_ticks = timer_mask_usec_ticks(6, pclk);
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tcfg1 &= ~S3C2410_TCFG1_MUX4_MASK;
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tcfg1 |= S3C2410_TCFG1_MUX4_DIV2;
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tcfg0 &= ~S3C2410_TCFG_PRESCALER1_MASK;
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tcfg0 |= ((6 - 1) / 2) << S3C2410_TCFG_PRESCALER1_SHIFT;
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tcnt = (pclk / 6) / HZ;
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}
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/* timers reload after counting zero, so reduce the count by 1 */
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tcnt--;
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printk("timer tcon=%08lx, tcnt %04lx, tcfg %08lx,%08lx, usec %08lx\n",
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tcon, tcnt, tcfg0, tcfg1, timer_usec_ticks);
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/* check to see if timer is within 16bit range... */
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if (tcnt > 0xffff) {
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panic("setup_timer: HZ is too small, cannot configure timer!");
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return;
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}
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__raw_writel(tcfg1, S3C2410_TCFG1);
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__raw_writel(tcfg0, S3C2410_TCFG0);
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timer_startval = tcnt;
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__raw_writel(tcnt, S3C2410_TCNTB(4));
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/* ensure timer is stopped... */
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tcon &= ~(7<<20);
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tcon |= S3C2410_TCON_T4RELOAD;
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tcon |= S3C2410_TCON_T4MANUALUPD;
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__raw_writel(tcon, S3C2410_TCON);
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__raw_writel(tcnt, S3C2410_TCNTB(4));
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__raw_writel(tcnt, S3C2410_TCMPB(4));
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/* start the timer running */
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tcon |= S3C2410_TCON_T4START;
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tcon &= ~S3C2410_TCON_T4MANUALUPD;
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__raw_writel(tcon, S3C2410_TCON);
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}
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static void __init s3c2410_timer_init (void)
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{
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s3c2410_timer_setup();
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setup_irq(IRQ_TIMER4, &s3c2410_timer_irq);
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}
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struct sys_timer s3c24xx_timer = {
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.init = s3c2410_timer_init,
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.offset = s3c2410_gettimeoffset,
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.resume = s3c2410_timer_setup
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};
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