john stultz | 8d016ef | 2006-06-26 00:25:09 -0700 | [diff] [blame] | 1 | /* |
| 2 | * i8253.c 8253/PIT functions |
| 3 | * |
| 4 | */ |
Thomas Gleixner | e9e2cdb | 2007-02-16 01:28:04 -0800 | [diff] [blame] | 5 | #include <linux/clockchips.h> |
john stultz | 8d016ef | 2006-06-26 00:25:09 -0700 | [diff] [blame] | 6 | #include <linux/spinlock.h> |
| 7 | #include <linux/jiffies.h> |
| 8 | #include <linux/sysdev.h> |
| 9 | #include <linux/module.h> |
| 10 | #include <linux/init.h> |
| 11 | |
| 12 | #include <asm/smp.h> |
| 13 | #include <asm/delay.h> |
| 14 | #include <asm/i8253.h> |
| 15 | #include <asm/io.h> |
| 16 | |
| 17 | #include "io_ports.h" |
| 18 | |
| 19 | DEFINE_SPINLOCK(i8253_lock); |
| 20 | EXPORT_SYMBOL(i8253_lock); |
| 21 | |
Thomas Gleixner | e9e2cdb | 2007-02-16 01:28:04 -0800 | [diff] [blame] | 22 | /* |
| 23 | * HPET replaces the PIT, when enabled. So we need to know, which of |
| 24 | * the two timers is used |
| 25 | */ |
| 26 | struct clock_event_device *global_clock_event; |
| 27 | |
| 28 | /* |
| 29 | * Initialize the PIT timer. |
| 30 | * |
| 31 | * This is also called after resume to bring the PIT into operation again. |
| 32 | */ |
| 33 | static void init_pit_timer(enum clock_event_mode mode, |
| 34 | struct clock_event_device *evt) |
john stultz | 8d016ef | 2006-06-26 00:25:09 -0700 | [diff] [blame] | 35 | { |
| 36 | unsigned long flags; |
| 37 | |
| 38 | spin_lock_irqsave(&i8253_lock, flags); |
Thomas Gleixner | e9e2cdb | 2007-02-16 01:28:04 -0800 | [diff] [blame] | 39 | |
| 40 | switch(mode) { |
| 41 | case CLOCK_EVT_MODE_PERIODIC: |
| 42 | /* binary, mode 2, LSB/MSB, ch 0 */ |
| 43 | outb_p(0x34, PIT_MODE); |
| 44 | udelay(10); |
| 45 | outb_p(LATCH & 0xff , PIT_CH0); /* LSB */ |
| 46 | udelay(10); |
| 47 | outb(LATCH >> 8 , PIT_CH0); /* MSB */ |
| 48 | break; |
| 49 | |
Thomas Gleixner | 6b3964c | 2007-03-22 22:46:18 +0100 | [diff] [blame] | 50 | /* |
| 51 | * Avoid unnecessary state transitions, as it confuses |
| 52 | * Geode / Cyrix based boxen. |
| 53 | */ |
Thomas Gleixner | e9e2cdb | 2007-02-16 01:28:04 -0800 | [diff] [blame] | 54 | case CLOCK_EVT_MODE_SHUTDOWN: |
Thomas Gleixner | 6b3964c | 2007-03-22 22:46:18 +0100 | [diff] [blame] | 55 | if (evt->mode == CLOCK_EVT_MODE_UNUSED) |
| 56 | break; |
Thomas Gleixner | e9e2cdb | 2007-02-16 01:28:04 -0800 | [diff] [blame] | 57 | case CLOCK_EVT_MODE_UNUSED: |
Thomas Gleixner | 6b3964c | 2007-03-22 22:46:18 +0100 | [diff] [blame] | 58 | if (evt->mode == CLOCK_EVT_MODE_SHUTDOWN) |
| 59 | break; |
| 60 | case CLOCK_EVT_MODE_ONESHOT: |
Thomas Gleixner | e9e2cdb | 2007-02-16 01:28:04 -0800 | [diff] [blame] | 61 | /* One shot setup */ |
| 62 | outb_p(0x38, PIT_MODE); |
| 63 | udelay(10); |
| 64 | break; |
| 65 | } |
john stultz | 8d016ef | 2006-06-26 00:25:09 -0700 | [diff] [blame] | 66 | spin_unlock_irqrestore(&i8253_lock, flags); |
| 67 | } |
john stultz | 5d0cf41 | 2006-06-26 00:25:12 -0700 | [diff] [blame] | 68 | |
| 69 | /* |
Thomas Gleixner | e9e2cdb | 2007-02-16 01:28:04 -0800 | [diff] [blame] | 70 | * Program the next event in oneshot mode |
| 71 | * |
| 72 | * Delta is given in PIT ticks |
| 73 | */ |
| 74 | static int pit_next_event(unsigned long delta, struct clock_event_device *evt) |
| 75 | { |
| 76 | unsigned long flags; |
| 77 | |
| 78 | spin_lock_irqsave(&i8253_lock, flags); |
| 79 | outb_p(delta & 0xff , PIT_CH0); /* LSB */ |
| 80 | outb(delta >> 8 , PIT_CH0); /* MSB */ |
| 81 | spin_unlock_irqrestore(&i8253_lock, flags); |
| 82 | |
| 83 | return 0; |
| 84 | } |
| 85 | |
| 86 | /* |
| 87 | * On UP the PIT can serve all of the possible timer functions. On SMP systems |
| 88 | * it can be solely used for the global tick. |
| 89 | * |
| 90 | * The profiling and update capabilites are switched off once the local apic is |
| 91 | * registered. This mechanism replaces the previous #ifdef LOCAL_APIC - |
| 92 | * !using_apic_timer decisions in do_timer_interrupt_hook() |
| 93 | */ |
| 94 | struct clock_event_device pit_clockevent = { |
| 95 | .name = "pit", |
| 96 | .features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT, |
| 97 | .set_mode = init_pit_timer, |
| 98 | .set_next_event = pit_next_event, |
| 99 | .shift = 32, |
| 100 | .irq = 0, |
| 101 | }; |
| 102 | |
| 103 | /* |
| 104 | * Initialize the conversion factor and the min/max deltas of the clock event |
| 105 | * structure and register the clock event source with the framework. |
| 106 | */ |
| 107 | void __init setup_pit_timer(void) |
| 108 | { |
| 109 | /* |
| 110 | * Start pit with the boot cpu mask and make it global after the |
| 111 | * IO_APIC has been initialized. |
| 112 | */ |
| 113 | pit_clockevent.cpumask = cpumask_of_cpu(0); |
| 114 | pit_clockevent.mult = div_sc(CLOCK_TICK_RATE, NSEC_PER_SEC, 32); |
| 115 | pit_clockevent.max_delta_ns = |
| 116 | clockevent_delta2ns(0x7FFF, &pit_clockevent); |
| 117 | pit_clockevent.min_delta_ns = |
| 118 | clockevent_delta2ns(0xF, &pit_clockevent); |
| 119 | clockevents_register_device(&pit_clockevent); |
| 120 | global_clock_event = &pit_clockevent; |
| 121 | } |
| 122 | |
| 123 | /* |
john stultz | 5d0cf41 | 2006-06-26 00:25:12 -0700 | [diff] [blame] | 124 | * Since the PIT overflows every tick, its not very useful |
| 125 | * to just read by itself. So use jiffies to emulate a free |
| 126 | * running counter: |
| 127 | */ |
| 128 | static cycle_t pit_read(void) |
| 129 | { |
| 130 | unsigned long flags; |
| 131 | int count; |
john stultz | 6415ce9 | 2006-06-26 00:25:16 -0700 | [diff] [blame] | 132 | u32 jifs; |
| 133 | static int old_count; |
| 134 | static u32 old_jifs; |
john stultz | 5d0cf41 | 2006-06-26 00:25:12 -0700 | [diff] [blame] | 135 | |
| 136 | spin_lock_irqsave(&i8253_lock, flags); |
Thomas Gleixner | e9e2cdb | 2007-02-16 01:28:04 -0800 | [diff] [blame] | 137 | /* |
john stultz | 6415ce9 | 2006-06-26 00:25:16 -0700 | [diff] [blame] | 138 | * Although our caller may have the read side of xtime_lock, |
| 139 | * this is now a seqlock, and we are cheating in this routine |
| 140 | * by having side effects on state that we cannot undo if |
| 141 | * there is a collision on the seqlock and our caller has to |
| 142 | * retry. (Namely, old_jifs and old_count.) So we must treat |
| 143 | * jiffies as volatile despite the lock. We read jiffies |
| 144 | * before latching the timer count to guarantee that although |
| 145 | * the jiffies value might be older than the count (that is, |
| 146 | * the counter may underflow between the last point where |
| 147 | * jiffies was incremented and the point where we latch the |
| 148 | * count), it cannot be newer. |
| 149 | */ |
| 150 | jifs = jiffies; |
john stultz | 5d0cf41 | 2006-06-26 00:25:12 -0700 | [diff] [blame] | 151 | outb_p(0x00, PIT_MODE); /* latch the count ASAP */ |
| 152 | count = inb_p(PIT_CH0); /* read the latched count */ |
| 153 | count |= inb_p(PIT_CH0) << 8; |
| 154 | |
| 155 | /* VIA686a test code... reset the latch if count > max + 1 */ |
| 156 | if (count > LATCH) { |
| 157 | outb_p(0x34, PIT_MODE); |
| 158 | outb_p(LATCH & 0xff, PIT_CH0); |
| 159 | outb(LATCH >> 8, PIT_CH0); |
| 160 | count = LATCH - 1; |
| 161 | } |
john stultz | 6415ce9 | 2006-06-26 00:25:16 -0700 | [diff] [blame] | 162 | |
| 163 | /* |
| 164 | * It's possible for count to appear to go the wrong way for a |
| 165 | * couple of reasons: |
| 166 | * |
| 167 | * 1. The timer counter underflows, but we haven't handled the |
| 168 | * resulting interrupt and incremented jiffies yet. |
| 169 | * 2. Hardware problem with the timer, not giving us continuous time, |
| 170 | * the counter does small "jumps" upwards on some Pentium systems, |
| 171 | * (see c't 95/10 page 335 for Neptun bug.) |
| 172 | * |
| 173 | * Previous attempts to handle these cases intelligently were |
| 174 | * buggy, so we just do the simple thing now. |
| 175 | */ |
| 176 | if (count > old_count && jifs == old_jifs) { |
| 177 | count = old_count; |
| 178 | } |
| 179 | old_count = count; |
| 180 | old_jifs = jifs; |
| 181 | |
john stultz | 5d0cf41 | 2006-06-26 00:25:12 -0700 | [diff] [blame] | 182 | spin_unlock_irqrestore(&i8253_lock, flags); |
| 183 | |
john stultz | 6415ce9 | 2006-06-26 00:25:16 -0700 | [diff] [blame] | 184 | count = (LATCH - 1) - count; |
john stultz | 5d0cf41 | 2006-06-26 00:25:12 -0700 | [diff] [blame] | 185 | |
| 186 | return (cycle_t)(jifs * LATCH) + count; |
| 187 | } |
| 188 | |
| 189 | static struct clocksource clocksource_pit = { |
| 190 | .name = "pit", |
| 191 | .rating = 110, |
| 192 | .read = pit_read, |
john stultz | 6415ce9 | 2006-06-26 00:25:16 -0700 | [diff] [blame] | 193 | .mask = CLOCKSOURCE_MASK(32), |
john stultz | 5d0cf41 | 2006-06-26 00:25:12 -0700 | [diff] [blame] | 194 | .mult = 0, |
| 195 | .shift = 20, |
| 196 | }; |
| 197 | |
| 198 | static int __init init_pit_clocksource(void) |
| 199 | { |
john stultz | 3f4a0b9 | 2006-10-17 00:09:32 -0700 | [diff] [blame] | 200 | if (num_possible_cpus() > 1) /* PIT does not scale! */ |
john stultz | 5d0cf41 | 2006-06-26 00:25:12 -0700 | [diff] [blame] | 201 | return 0; |
| 202 | |
| 203 | clocksource_pit.mult = clocksource_hz2mult(CLOCK_TICK_RATE, 20); |
john stultz | a275254 | 2006-06-26 00:25:14 -0700 | [diff] [blame] | 204 | return clocksource_register(&clocksource_pit); |
john stultz | 5d0cf41 | 2006-06-26 00:25:12 -0700 | [diff] [blame] | 205 | } |
john stultz | 6bb74df | 2007-03-05 00:30:50 -0800 | [diff] [blame] | 206 | arch_initcall(init_pit_clocksource); |