1 /* linux/include/asm-arm/arch-s3c2410/time.h
3 * Copyright (C) 2003 Simtec Electronics <linux@simtec.co.uk>
4 * Ben Dooks, <ben@simtec.co.uk>
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
21 #include <asm/system.h>
23 #include <asm/mach-types.h>
26 #include <asm/arch/map.h>
27 #include <asm/arch/regs-timer.h>
29 extern unsigned long (*gettimeoffset)(void);
31 static unsigned long timer_startval;
32 static unsigned long timer_ticks_usec;
34 #ifdef CONFIG_S3C2410_RTC
35 extern void s3c2410_rtc_check();
38 /* with an 12MHz clock, we get 12 ticks per-usec
43 * Returns microsecond since last clock interrupt. Note that interrupts
44 * will have been disabled by do_gettimeoffset()
45 * IRQs are disabled before entering here from do_gettimeofday()
47 static unsigned long s3c2410_gettimeoffset (void)
52 /* work out how many ticks have gone since last timer interrupt */
54 tdone = timer_startval - __raw_readl(S3C2410_TCNTO(4));
56 /* currently, tcnt is in 12MHz units, but this may change
57 * for non-bast machines...
60 usec = tdone / timer_ticks_usec;
67 * IRQ handler for the timer
70 s3c2410_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
76 //s3c2410_rtc_check();
83 * Set up timer interrupt, and return the current time in seconds.
86 /* currently we only use timer4, as it is the only timer which has no
87 * other function that can be exploited externally
90 void __init time_init (void)
97 gettimeoffset = s3c2410_gettimeoffset;
98 timer_irq.handler = s3c2410_timer_interrupt;
100 tcnt = 0xffff; /* default value for tcnt */
102 /* read the current timer configuration bits */
104 tcon = __raw_readl(S3C2410_TCON);
105 tcfg1 = __raw_readl(S3C2410_TCFG1);
106 tcfg0 = __raw_readl(S3C2410_TCFG0);
108 /* configure the system for whichever machine is in use */
110 if (machine_is_bast() || machine_is_vr1000()) {
111 timer_ticks_usec = 12; /* timer is at 12MHz */
112 tcnt = (timer_ticks_usec * (1000*1000)) / HZ;
115 /* for the h1940, we use the pclk from the core to generate
116 * the timer values. since 67.5MHz is not a value we can directly
117 * generate the timer value from, we need to pre-scale and
118 * divied before using it.
120 * overall divsior to get 200Hz is 337500
121 * we can fit tcnt if we pre-scale by 6, producing a tick rate
122 * of 11.25MHz, and a tcnt of 56250.
125 if (machine_is_h1940() || machine_is_smdk2410() ) {
126 timer_ticks_usec = s3c2410_pclk / (1000*1000);
127 timer_ticks_usec /= 6;
129 tcfg1 &= ~S3C2410_TCFG1_MUX4_MASK;
130 tcfg1 |= S3C2410_TCFG1_MUX4_DIV2;
132 tcfg0 &= ~S3C2410_TCFG_PRESCALER1_MASK;
133 tcfg0 |= ((6 - 1) / 2) << S3C2410_TCFG_PRESCALER1_SHIFT;
135 tcnt = (s3c2410_pclk / 6) / HZ;
139 printk("setup_timer tcon=%08lx, tcnt %04lx, tcfg %08lx,%08lx\n",
140 tcon, tcnt, tcfg0, tcfg1);
142 /* check to see if timer is within 16bit range... */
144 panic("setup_timer: HZ is too small, cannot configure timer!");
148 __raw_writel(tcfg1, S3C2410_TCFG1);
149 __raw_writel(tcfg0, S3C2410_TCFG0);
151 timer_startval = tcnt;
152 __raw_writel(tcnt, S3C2410_TCNTB(4));
154 /* ensure timer is stopped... */
157 tcon |= S3C2410_TCON_T4RELOAD;
158 tcon |= S3C2410_TCON_T4MANUALUPD;
160 __raw_writel(tcon, S3C2410_TCON);
161 __raw_writel(tcnt, S3C2410_TCNTB(4));
162 __raw_writel(tcnt, S3C2410_TCMPB(4));
164 setup_irq(IRQ_TIMER4, &timer_irq);
166 /* start the timer running */
167 tcon |= S3C2410_TCON_T4START;
168 tcon &= ~S3C2410_TCON_T4MANUALUPD;
169 __raw_writel(tcon, S3C2410_TCON);