1/* 2 * linux/include/asm-arm/arch-sa1100/time.h 3 * 4 * Copyright (C) 1998 Deborah Wallach. 5 * Twiddles (C) 1999 Hugo Fiennes <hugo@empeg.com> 6 * 7 * 2000/03/29 (C) Nicolas Pitre <nico@cam.org> 8 * Rewritten: big cleanup, much simpler, better HZ accuracy. 9 * 10 */ 11 12 13#define RTC_DEF_DIVIDER (32768 - 1) 14#define RTC_DEF_TRIM 0 15 16static unsigned long __init sa1100_get_rtc_time(void) 17{ 18 /* 19 * According to the manual we should be able to let RTTR be zero 20 * and then a default diviser for a 32.768KHz clock is used. 21 * Apparently this doesn't work, at least for my SA1110 rev 5. 22 * If the clock divider is uninitialized then reset it to the 23 * default value to get the 1Hz clock. 24 */ 25 if (RTTR == 0) { 26 RTTR = RTC_DEF_DIVIDER + (RTC_DEF_TRIM << 16); 27 printk(KERN_WARNING "Warning: uninitialized Real Time Clock\n"); 28 /* The current RTC value probably doesn't make sense either */ 29 RCNR = 0; 30 return 0; 31 } 32 return RCNR; 33} 34 35static int sa1100_set_rtc(void) 36{ 37 unsigned long current_time = xtime.tv_sec; 38 39 if (RTSR & RTSR_ALE) { 40 /* make sure not to forward the clock over an alarm */ 41 unsigned long alarm = RTAR; 42 if (current_time >= alarm && alarm >= RCNR) 43 return -ERESTARTSYS; 44 } 45 RCNR = current_time; 46 return 0; 47} 48 49/* IRQs are disabled before entering here from do_gettimeofday() */ 50static unsigned long sa1100_gettimeoffset (void) 51{ 52 unsigned long ticks_to_match, elapsed, usec; 53 54 /* Get ticks before next timer match */ 55 ticks_to_match = OSMR0 - OSCR; 56 57 /* We need elapsed ticks since last match */ 58 elapsed = LATCH - ticks_to_match; 59 60 /* Now convert them to usec */ 61 usec = (unsigned long)(elapsed*tick)/LATCH; 62 63 return usec; 64} 65 66static void sa1100_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs) 67{ 68 long flags; 69 int next_match; 70 71 /* Loop until we get ahead of the free running timer. 72 * This ensures an exact clock tick count and time acuracy. 73 * IRQs are disabled inside the loop to ensure coherence between 74 * lost_ticks (updated in do_timer()) and the match reg value, so we 75 * can use do_gettimeofday() from interrupt handlers. 76 */ 77 do { 78 do_leds(); 79 do_set_rtc(); 80 save_flags_cli( flags ); 81 do_timer(regs); 82 OSSR = OSSR_M0; /* Clear match on timer 0 */ 83 next_match = (OSMR0 += LATCH); 84 restore_flags( flags ); 85 } while( (signed long)(next_match - OSCR) <= 0 ); 86} 87 88static inline void setup_timer (void) 89{ 90 gettimeoffset = sa1100_gettimeoffset; 91 set_rtc = sa1100_set_rtc; 92 xtime.tv_sec = sa1100_get_rtc_time(); 93 timer_irq.handler = sa1100_timer_interrupt; 94 OSMR0 = 0; /* set initial match at 0 */ 95 OSSR = 0xf; /* clear status on all timers */ 96 setup_arm_irq(IRQ_OST0, &timer_irq); 97 OIER |= OIER_E0; /* enable match on timer 0 to cause interrupts */ 98 OSCR = 0; /* initialize free-running timer, force first match */ 99} 100 101