/* linux/arch/arm/mach-s3c2410/time.c
*
* Copyright (C) 2003-2005 Simtec Electronics
* Ben Dooks, <ben@simtec.co.uk>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <linux/config.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/err.h>
#include <linux/clk.h>
#include <asm/system.h>
#include <asm/leds.h>
#include <asm/mach-types.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <asm/arch/map.h>
#include <asm/arch/regs-timer.h>
#include <asm/arch/regs-irq.h>
#include <asm/mach/time.h>
#include "clock.h"
#include "cpu.h"
static unsigned long timer_startval;
static unsigned long timer_usec_ticks;
#define TIMER_USEC_SHIFT 16
/* we use the shifted arithmetic to work out the ratio of timer ticks
* to usecs, as often the peripheral clock is not a nice even multiple
* of 1MHz.
*
* shift of 14 and 15 are too low for the 12MHz, 16 seems to be ok
* for the current HZ value of 200 without producing overflows.
*
* Original patch by Dimitry Andric, updated by Ben Dooks
*/
/* timer_mask_usec_ticks
*
* given a clock and divisor, make the value to pass into timer_ticks_to_usec
* to scale the ticks into usecs
*/
static inline unsigned long
timer_mask_usec_ticks(unsigned long scaler, unsigned long pclk)
{
unsigned long den = pclk / 1000;
return ((1000 << TIMER_USEC_SHIFT) * scaler + (den >> 1)) / den;
}
/* timer_ticks_to_usec
*
* convert timer ticks to usec.
*/
static inline unsigned long timer_ticks_to_usec(unsigned long ticks)
{
unsigned long res;
res = ticks * timer_usec_ticks;
res += 1 << (TIMER_USEC_SHIFT - 4); /* round up slightly */
return res >> TIMER_USEC_SHIFT;
}
/***
* Returns microsecond since last clock interrupt. Note that interrupts
* will have been disabled by do_gettimeoffset()
* IRQs are disabled before entering here from do_gettimeofday()
*/
#define SRCPND_TIMER4 (1<<(IRQ_TIMER4 - IRQ_EINT0))
static unsigned long s3c2410_gettimeoffset (void)
{
unsigned long tdone;
unsigned long irqpend;
unsigned long tval;
/* work out how many ticks have gone since last timer interrupt */
tval = __raw_readl(S3C2410_TCNTO(4));
tdone = timer_startval - tval;
/* check to see if there is an interrupt pending */
irqpend = __raw_readl(S3C2410_SRCPND);
if (irqpend & SRCPND_TIMER4) {
/* re-read the timer, and try and fix up for the missed
* interrupt. Note, the interrupt may go off before the
* timer has re-loaded from wrapping.
*/
tval = __raw_readl(S3C2410_TCNTO(4));
tdone = timer_startval - tval;
if (tval != 0)
tdone += timer_startval;
}
return timer_ticks_to_usec(tdone);
}
/*
* IRQ handler for the timer
*/
static irqreturn_t
s3c2410_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
write_seqlock(&xtime_lock);
timer_tick(regs);
write_sequnlock(&xtime_lock);
return IRQ_HANDLED;
}
static struct irqaction s3c2410_timer_irq = {
.name = "S3C2410 Timer Tick",
.flags = SA_INTERRUPT | SA_TIMER,
.handler = s3c2410_timer_interrupt,
};
#define use_tclk1_12() ( \
machine_is_bast() || \
machine_is_vr1000() || \
machine_is_anubis() || \
machine_is_osiris() )
/*
* Set up timer interrupt, and return the current time in seconds.
*
* Currently we only use timer4, as it is the only timer which has no
* other function that can be exploited externally
*/
static void s3c2410_timer_setup (void)
{
unsigned long tcon;
unsigned long tcnt;
unsigned long tcfg1;
unsigned long tcfg0;
tcnt = 0xffff; /* default value for tcnt */
/* read the current timer configuration bits */
tcon = __raw_readl(S3C2410_TCON);
tcfg1 = __raw_readl(S3C2410_TCFG1);
tcfg0 = __raw_readl(S3C2410_TCFG0);
/* configure the system for whichever machine is in use */
if (use_tclk1_12()) {
/* timer is at 12MHz, scaler is 1 */
timer_usec_ticks = timer_mask_usec_ticks(1, 12000000);
tcnt = 12000000 / HZ;
tcfg1 &= ~S3C2410_TCFG1_MUX4_MASK;
tcfg1 |= S3C2410_TCFG1_MUX4_TCLK1;
} else {
unsigned long pclk;
struct clk *clk;
/* for the h1940 (and others), we use the pclk from the core
* to generate the timer values. since values around 50 to
* 70MHz are not values we can directly generate the timer
* value from, we need to pre-scale and divide before using it.
*
* for instance, using 50.7MHz and dividing by 6 gives 8.45MHz
* (8.45 ticks per usec)
*/
/* this is used as default if no other timer can be found */
clk = clk_get(NULL, "timers");
if (IS_ERR(clk))
panic("failed to get clock for system timer");
clk_enable(clk);
pclk = clk_get_rate(clk);
/* configure clock tick */
timer_usec_ticks = timer_mask_usec_ticks(6, pclk);
tcfg1 &= ~S3C2410_TCFG1_MUX4_MASK;
tcfg1 |= S3C2410_TCFG1_MUX4_DIV2;
tcfg0 &= ~S3C2410_TCFG_PRESCALER1_MASK;
tcfg0 |= ((6 - 1) / 2) << S3C2410_TCFG_PRESCALER1_SHIFT;
tcnt = (pclk / 6) / HZ;
}
/* timers reload after counting zero, so reduce the count by 1 */
tcnt--;
printk("timer tcon=%08lx, tcnt %04lx, tcfg %08lx,%08lx, usec %08lx\n",
tcon, tcnt, tcfg0, tcfg1, timer_usec_ticks);
/* check to see if timer is within 16bit range... */
if (tcnt > 0xffff) {
panic("setup_timer: HZ is too small, cannot configure timer!");
return;
}
__raw_writel(tcfg1, S3C2410_TCFG1);
__raw_writel(tcfg0, S3C2410_TCFG0);
timer_startval = tcnt;
__raw_writel(tcnt, S3C2410_TCNTB(4));
/* ensure timer is stopped... */
tcon &= ~(7<<20);
tcon |= S3C2410_TCON_T4RELOAD;
tcon |= S3C2410_TCON_T4MANUALUPD;
__raw_writel(tcon, S3C2410_TCON);
__raw_writel(tcnt, S3C2410_TCNTB(4));
__raw_writel(tcnt, S3C2410_TCMPB(4));
/* start the timer running */
tcon |= S3C2410_TCON_T4START;
tcon &= ~S3C2410_TCON_T4MANUALUPD;
__raw_writel(tcon, S3C2410_TCON);
}
static void __init s3c2410_timer_init (void)
{
s3c2410_timer_setup();
setup_irq(IRQ_TIMER4, &s3c2410_timer_irq);
}
struct sys_timer s3c24xx_timer = {
.init = s3c2410_timer_init,
.offset = s3c2410_gettimeoffset,
.resume = s3c2410_timer_setup
};
