diff options
Diffstat (limited to 'arch/arm/mach-s3c2410/time.c')
| -rw-r--r-- | arch/arm/mach-s3c2410/time.c | 256 |
1 files changed, 256 insertions, 0 deletions
diff --git a/arch/arm/mach-s3c2410/time.c b/arch/arm/mach-s3c2410/time.c new file mode 100644 index 000000000000..179f0e031af4 --- /dev/null +++ b/arch/arm/mach-s3c2410/time.c @@ -0,0 +1,256 @@ +/* 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 <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 <asm/hardware/clock.h> + +#include "clock.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, + .handler = s3c2410_timer_interrupt +}; + +/* + * 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 (machine_is_bast() || machine_is_vr1000()) { + /* 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_use(clk); + 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 +}; |