arch/blackfin/kernel/time.c

   1 /*
   2  * File:         arch/blackfin/kernel/time.c
   3  * Based on:     none - original work
   4  * Author:
   5  *
   6  * Created:
   7  * Description:  This file contains the bfin-specific time handling details.
   8  *               Most of the stuff is located in the machine specific files.
   9  *
  10  * Modified:
  11  *               Copyright 2004-2006 Analog Devices Inc.
  12  *
  13  * Bugs:         Enter bugs at http://blackfin.uclinux.org/
  14  *
  15  * This program is free software; you can redistribute it and/or modify
  16  * it under the terms of the GNU General Public License as published by
  17  * the Free Software Foundation; either version 2 of the License, or
  18  * (at your option) any later version.
  19  *
  20  * This program is distributed in the hope that it will be useful,
  21  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  22  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  23  * GNU General Public License for more details.
  24  *
  25  * You should have received a copy of the GNU General Public License
  26  * along with this program; if not, see the file COPYING, or write
  27  * to the Free Software Foundation, Inc.,
  28  * 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  29  */
  30
  31 #include <linux/module.h>
  32 #include <linux/profile.h>
  33 #include <linux/interrupt.h>
  34 #include <linux/time.h>
  35 #include <linux/irq.h>
  36
  37 #include <asm/blackfin.h>
  38
  39 /* This is an NTP setting */
  40 #define TICK_SIZE (tick_nsec / 1000)
  41
  42 static void time_sched_init(irqreturn_t(*timer_routine)
  43                         (int, void *));
  44 static unsigned long gettimeoffset(void);
  45
  46 static struct irqaction bfin_timer_irq = {
  47         .name = "BFIN Timer Tick",
  48         .flags = IRQF_DISABLED
  49 };
  50
  51 /*
  52  * The way that the Blackfin core timer works is:
  53  *  - CCLK is divided by a programmable 8-bit pre-scaler (TSCALE)
  54  *  - Every time TSCALE ticks, a 32bit is counted down (TCOUNT)
  55  *
  56  * If you take the fastest clock (1ns, or 1GHz to make the math work easier)
  57  *    10ms is 10,000,000 clock ticks, which fits easy into a 32-bit counter
  58  *    (32 bit counter is 4,294,967,296ns or 4.2 seconds) so, we don't need
  59  *    to use TSCALE, and program it to zero (which is pass CCLK through).
  60  *    If you feel like using it, try to keep HZ * TIMESCALE to some
  61  *    value that divides easy (like power of 2).
  62  */
  63
  64 #define TIME_SCALE 1
  65
  66 static void
  67 time_sched_init(irqreturn_t(*timer_routine) (int, void *))
  68 {
  69         u32 tcount;
  70
  71         /* power up the timer, but don't enable it just yet */
  72         bfin_write_TCNTL(1);
  73         CSYNC();
  74
  75         /*
  76          * the TSCALE prescaler counter.
  77          */
  78         bfin_write_TSCALE((TIME_SCALE - 1));
  79
  80         tcount = ((get_cclk() / (HZ * TIME_SCALE)) - 1);
  81         bfin_write_TPERIOD(tcount);
  82         bfin_write_TCOUNT(tcount);
  83
  84         /* now enable the timer */
  85         CSYNC();
  86
  87         bfin_write_TCNTL(7);
  88
  89         bfin_timer_irq.handler = (irq_handler_t)timer_routine;
  90         /* call setup_irq instead of request_irq because request_irq calls
  91          * kmalloc which has not been initialized yet
  92          */
  93         setup_irq(IRQ_CORETMR, &bfin_timer_irq);
  94 }
  95
  96 /*
  97  * Should return useconds since last timer tick
  98  */
  99 static unsigned long gettimeoffset(void)
 100 {
 101         unsigned long offset;
 102         unsigned long clocks_per_jiffy;
 103
 104         clocks_per_jiffy = bfin_read_TPERIOD();
 105         offset =
 106             (clocks_per_jiffy -
 107              bfin_read_TCOUNT()) / (((clocks_per_jiffy + 1) * HZ) /
 108                                     USEC_PER_SEC);
 109
 110         /* Check if we just wrapped the counters and maybe missed a tick */
 111         if ((bfin_read_ILAT() & (1 << IRQ_CORETMR))
 112             && (offset < (100000 / HZ / 2)))
 113                 offset += (USEC_PER_SEC / HZ);
 114
 115         return offset;
 116 }
 117
 118 static inline int set_rtc_mmss(unsigned long nowtime)
 119 {
 120         return 0;
 121 }
 122
 123 /*
 124  * timer_interrupt() needs to keep up the real-time clock,
 125  * as well as call the "do_timer()" routine every clocktick
 126  */
 127 #ifdef CONFIG_CORE_TIMER_IRQ_L1
 128 irqreturn_t timer_interrupt(int irq, void *dummy)__attribute__((l1_text));
 129 #endif
 130
 131 irqreturn_t timer_interrupt(int irq, void *dummy)
 132 {
 133         /* last time the cmos clock got updated */
 134         static long last_rtc_update;
 135
 136         write_seqlock(&xtime_lock);
 137
 138         do_timer(1);
 139
 140 #ifndef CONFIG_SMP
 141         update_process_times(user_mode(get_irq_regs()));
 142 #endif
 143         profile_tick(CPU_PROFILING);
 144
 145         /*
 146          * If we have an externally synchronized Linux clock, then update
 147          * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
 148          * called as close as possible to 500 ms before the new second starts.
 149          */
 150
 151         if (ntp_synced() &&
 152             xtime.tv_sec > last_rtc_update + 660 &&
 153             (xtime.tv_nsec / NSEC_PER_USEC) >=
 154             500000 - ((unsigned)TICK_SIZE) / 2
 155             && (xtime.tv_nsec / NSEC_PER_USEC) <=
 156             500000 + ((unsigned)TICK_SIZE) / 2) {
 157                 if (set_rtc_mmss(xtime.tv_sec) == 0)
 158                         last_rtc_update = xtime.tv_sec;
 159                 else
 160                         /* Do it again in 60s. */
 161                         last_rtc_update = xtime.tv_sec - 600;
 162         }
 163         write_sequnlock(&xtime_lock);
 164         return IRQ_HANDLED;
 165 }
 166
 167 void __init time_init(void)
 168 {
 169         time_t secs_since_1970 = (365 * 37 + 9) * 24 * 60 * 60; /* 1 Jan 2007 */
 170
 171 #ifdef CONFIG_RTC_DRV_BFIN
 172         /* [#2663] hack to filter junk RTC values that would cause
 173          * userspace to have to deal with time values greater than
 174          * 2^31 seconds (which uClibc cannot cope with yet)
 175          */
 176         if ((bfin_read_RTC_STAT() & 0xC0000000) == 0xC0000000) {
 177                 printk(KERN_NOTICE "bfin-rtc: invalid date; resetting\n");
 178                 bfin_write_RTC_STAT(0);
 179         }
 180 #endif
 181
 182         /* Initialize xtime. From now on, xtime is updated with timer interrupts */
 183         xtime.tv_sec = secs_since_1970;
 184         xtime.tv_nsec = 0;
 185
 186         wall_to_monotonic.tv_sec = -xtime.tv_sec;
 187
 188         time_sched_init(timer_interrupt);
 189 }
 190
 191 #ifndef CONFIG_GENERIC_TIME
 192 void do_gettimeofday(struct timeval *tv)
 193 {
 194         unsigned long flags;
 195         unsigned long seq;
 196         unsigned long usec, sec;
 197
 198         do {
 199                 seq = read_seqbegin_irqsave(&xtime_lock, flags);
 200                 usec = gettimeoffset();
 201                 sec = xtime.tv_sec;
 202                 usec += (xtime.tv_nsec / NSEC_PER_USEC);
 203         }
 204         while (read_seqretry_irqrestore(&xtime_lock, seq, flags));
 205
 206         while (usec >= USEC_PER_SEC) {
 207                 usec -= USEC_PER_SEC;
 208                 sec++;
 209         }
 210
 211         tv->tv_sec = sec;
 212         tv->tv_usec = usec;
 213 }
 214 EXPORT_SYMBOL(do_gettimeofday);
 215
 216 int do_settimeofday(struct timespec *tv)
 217 {
 218         time_t wtm_sec, sec = tv->tv_sec;
 219         long wtm_nsec, nsec = tv->tv_nsec;
 220
 221         if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
 222                 return -EINVAL;
 223
 224         write_seqlock_irq(&xtime_lock);
 225         /*
 226          * This is revolting. We need to set the xtime.tv_usec
 227          * correctly. However, the value in this location is
 228          * is value at the last tick.
 229          * Discover what correction gettimeofday
 230          * would have done, and then undo it!
 231          */
 232         nsec -= (gettimeoffset() * NSEC_PER_USEC);
 233
 234         wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
 235         wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);
 236
 237         set_normalized_timespec(&xtime, sec, nsec);
 238         set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
 239
 240         ntp_clear();
 241
 242         write_sequnlock_irq(&xtime_lock);
 243         clock_was_set();
 244
 245         return 0;
 246 }
 247 EXPORT_SYMBOL(do_settimeofday);
 248 #endif /* !CONFIG_GENERIC_TIME */
 249
 250 /*
 251  * Scheduler clock - returns current time in nanosec units.
 252  */
 253 unsigned long long sched_clock(void)
 254 {
 255         return (unsigned long long)jiffies *(NSEC_PER_SEC / HZ);
 256 }