1/* linux/arch/arm/plat-samsung/time.c 2 * 3 * Copyright (C) 2003-2005 Simtec Electronics 4 * Ben Dooks, <ben@simtec.co.uk> 5 * 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. 10 * 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. 15 * 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 19 */ 20 21#include <linux/kernel.h> 22#include <linux/sched.h> 23#include <linux/init.h> 24#include <linux/interrupt.h> 25#include <linux/irq.h> 26#include <linux/err.h> 27#include <linux/clk.h> 28#include <linux/io.h> 29#include <linux/platform_device.h> 30 31#include <asm/system.h> 32#include <asm/leds.h> 33#include <asm/mach-types.h> 34 35#include <asm/irq.h> 36#include <mach/map.h> 37#include <plat/regs-timer.h> 38#include <mach/regs-irq.h> 39#include <asm/mach/time.h> 40#include <mach/tick.h> 41 42#include <plat/clock.h> 43#include <plat/cpu.h> 44 45static unsigned long timer_startval; 46static unsigned long timer_usec_ticks; 47 48#ifndef TICK_MAX 49#define TICK_MAX (0xffff) 50#endif 51 52#define TIMER_USEC_SHIFT 16 53 54/* we use the shifted arithmetic to work out the ratio of timer ticks 55 * to usecs, as often the peripheral clock is not a nice even multiple 56 * of 1MHz. 57 * 58 * shift of 14 and 15 are too low for the 12MHz, 16 seems to be ok 59 * for the current HZ value of 200 without producing overflows. 60 * 61 * Original patch by Dimitry Andric, updated by Ben Dooks 62*/ 63 64 65/* timer_mask_usec_ticks 66 * 67 * given a clock and divisor, make the value to pass into timer_ticks_to_usec 68 * to scale the ticks into usecs 69*/ 70 71static inline unsigned long 72timer_mask_usec_ticks(unsigned long scaler, unsigned long pclk) 73{ 74 unsigned long den = pclk / 1000; 75 76 return ((1000 << TIMER_USEC_SHIFT) * scaler + (den >> 1)) / den; 77} 78 79/* timer_ticks_to_usec 80 * 81 * convert timer ticks to usec. 82*/ 83 84static inline unsigned long timer_ticks_to_usec(unsigned long ticks) 85{ 86 unsigned long res; 87 88 res = ticks * timer_usec_ticks; 89 res += 1 << (TIMER_USEC_SHIFT - 4); /* round up slightly */ 90 91 return res >> TIMER_USEC_SHIFT; 92} 93 94/*** 95 * Returns microsecond since last clock interrupt. Note that interrupts 96 * will have been disabled by do_gettimeoffset() 97 * IRQs are disabled before entering here from do_gettimeofday() 98 */ 99 100static unsigned long s3c2410_gettimeoffset (void) 101{ 102 unsigned long tdone; 103 unsigned long tval; 104 105 /* work out how many ticks have gone since last timer interrupt */ 106 107 tval = __raw_readl(S3C2410_TCNTO(4)); 108 tdone = timer_startval - tval; 109 110 /* check to see if there is an interrupt pending */ 111 112 if (s3c24xx_ostimer_pending()) { 113 /* re-read the timer, and try and fix up for the missed 114 * interrupt. Note, the interrupt may go off before the 115 * timer has re-loaded from wrapping. 116 */ 117 118 tval = __raw_readl(S3C2410_TCNTO(4)); 119 tdone = timer_startval - tval; 120 121 if (tval != 0) 122 tdone += timer_startval; 123 } 124 125 return timer_ticks_to_usec(tdone); 126} 127 128 129/* 130 * IRQ handler for the timer 131 */ 132static irqreturn_t 133s3c2410_timer_interrupt(int irq, void *dev_id) 134{ 135 timer_tick(); 136 return IRQ_HANDLED; 137} 138 139static struct irqaction s3c2410_timer_irq = { 140 .name = "S3C2410 Timer Tick", 141 .flags = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL, 142 .handler = s3c2410_timer_interrupt, 143}; 144 145#define use_tclk1_12() ( \ 146 machine_is_bast() || \ 147 machine_is_vr1000() || \ 148 machine_is_anubis() || \ 149 machine_is_osiris()) 150 151static struct clk *tin; 152static struct clk *tdiv; 153static struct clk *timerclk; 154 155/* 156 * Set up timer interrupt, and return the current time in seconds. 157 * 158 * Currently we only use timer4, as it is the only timer which has no 159 * other function that can be exploited externally 160 */ 161static void s3c2410_timer_setup (void) 162{ 163 unsigned long tcon; 164 unsigned long tcnt; 165 unsigned long tcfg1; 166 unsigned long tcfg0; 167 168 tcnt = TICK_MAX; /* default value for tcnt */ 169 170 /* configure the system for whichever machine is in use */ 171 172 if (use_tclk1_12()) { 173 /* timer is at 12MHz, scaler is 1 */ 174 timer_usec_ticks = timer_mask_usec_ticks(1, 12000000); 175 tcnt = 12000000 / HZ; 176 177 tcfg1 = __raw_readl(S3C2410_TCFG1); 178 tcfg1 &= ~S3C2410_TCFG1_MUX4_MASK; 179 tcfg1 |= S3C2410_TCFG1_MUX4_TCLK1; 180 __raw_writel(tcfg1, S3C2410_TCFG1); 181 } else { 182 unsigned long pclk; 183 struct clk *tscaler; 184 185 /* for the h1940 (and others), we use the pclk from the core 186 * to generate the timer values. since values around 50 to 187 * 70MHz are not values we can directly generate the timer 188 * value from, we need to pre-scale and divide before using it. 189 * 190 * for instance, using 50.7MHz and dividing by 6 gives 8.45MHz 191 * (8.45 ticks per usec) 192 */ 193 194 pclk = clk_get_rate(timerclk); 195 196 /* configure clock tick */ 197 198 timer_usec_ticks = timer_mask_usec_ticks(6, pclk); 199 200 tscaler = clk_get_parent(tdiv); 201 202 clk_set_rate(tscaler, pclk / 3); 203 clk_set_rate(tdiv, pclk / 6); 204 clk_set_parent(tin, tdiv); 205 206 tcnt = clk_get_rate(tin) / HZ; 207 } 208 209 tcon = __raw_readl(S3C2410_TCON); 210 tcfg0 = __raw_readl(S3C2410_TCFG0); 211 tcfg1 = __raw_readl(S3C2410_TCFG1); 212 213 /* timers reload after counting zero, so reduce the count by 1 */ 214 215 tcnt--; 216 217 printk(KERN_DEBUG "timer tcon=%08lx, tcnt %04lx, tcfg %08lx,%08lx, usec %08lx\n", 218 tcon, tcnt, tcfg0, tcfg1, timer_usec_ticks); 219 220 /* check to see if timer is within 16bit range... */ 221 if (tcnt > TICK_MAX) { 222 panic("setup_timer: HZ is too small, cannot configure timer!"); 223 return; 224 } 225 226 __raw_writel(tcfg1, S3C2410_TCFG1); 227 __raw_writel(tcfg0, S3C2410_TCFG0); 228 229 timer_startval = tcnt; 230 __raw_writel(tcnt, S3C2410_TCNTB(4)); 231 232 /* ensure timer is stopped... */ 233 234 tcon &= ~(7<<20); 235 tcon |= S3C2410_TCON_T4RELOAD; 236 tcon |= S3C2410_TCON_T4MANUALUPD; 237 238 __raw_writel(tcon, S3C2410_TCON); 239 __raw_writel(tcnt, S3C2410_TCNTB(4)); 240 __raw_writel(tcnt, S3C2410_TCMPB(4)); 241 242 /* start the timer running */ 243 tcon |= S3C2410_TCON_T4START; 244 tcon &= ~S3C2410_TCON_T4MANUALUPD; 245 __raw_writel(tcon, S3C2410_TCON); 246} 247 248static void __init s3c2410_timer_resources(void) 249{ 250 struct platform_device tmpdev; 251 252 tmpdev.dev.bus = &platform_bus_type; 253 tmpdev.id = 4; 254 255 timerclk = clk_get(NULL, "timers"); 256 if (IS_ERR(timerclk)) 257 panic("failed to get clock for system timer"); 258 259 clk_enable(timerclk); 260 261 if (!use_tclk1_12()) { 262 tin = clk_get(&tmpdev.dev, "pwm-tin"); 263 if (IS_ERR(tin)) 264 panic("failed to get pwm-tin clock for system timer"); 265 266 tdiv = clk_get(&tmpdev.dev, "pwm-tdiv"); 267 if (IS_ERR(tdiv)) 268 panic("failed to get pwm-tdiv clock for system timer"); 269 } 270 271 clk_enable(tin); 272} 273 274static void __init s3c2410_timer_init(void) 275{ 276 s3c2410_timer_resources(); 277 s3c2410_timer_setup(); 278 setup_irq(IRQ_TIMER4, &s3c2410_timer_irq); 279} 280 281struct sys_timer s3c24xx_timer = { 282 .init = s3c2410_timer_init, 283 .offset = s3c2410_gettimeoffset, 284 .resume = s3c2410_timer_setup 285}; 286