scoutos / prex-0.9.0 / bsp / hal / x86 / pc / clock.c @ 03e9c04a
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1 | 03e9c04a | Brad Neuman | /*-
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2 | * Copyright (c) 2005-2007, Kohsuke Ohtani
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3 | * All rights reserved.
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4 | *
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5 | * Redistribution and use in source and binary forms, with or without
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6 | * modification, are permitted provided that the following conditions
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7 | * are met:
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8 | * 1. Redistributions of source code must retain the above copyright
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9 | * notice, this list of conditions and the following disclaimer.
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10 | * 2. Redistributions in binary form must reproduce the above copyright
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11 | * notice, this list of conditions and the following disclaimer in the
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12 | * documentation and/or other materials provided with the distribution.
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13 | * 3. Neither the name of the author nor the names of any co-contributors
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14 | * may be used to endorse or promote products derived from this software
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15 | * without specific prior written permission.
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16 | *
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17 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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18 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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19 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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20 | * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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21 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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22 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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23 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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24 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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25 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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26 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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27 | * SUCH DAMAGE.
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28 | */
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29 | |||
30 | /*
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31 | * clock.c - clock driver for i8254.
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32 | */
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33 | |||
34 | #include <kernel.h> |
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35 | #include <timer.h> |
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36 | #include <irq.h> |
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37 | #include <sys/ipl.h> |
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38 | #include <cpufunc.h> |
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39 | |||
40 | /* Interrupt vector for clock */
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41 | #define CLOCK_IRQ 0 |
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42 | |||
43 | /* The internal tick rate in ticks per second */
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44 | #define PIT_TICK 1193180L |
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45 | |||
46 | /* The latch count value for the current HZ setting */
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47 | #define PIT_LATCH ((PIT_TICK + (HZ / 2)) / HZ) |
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48 | |||
49 | /* I/O port for programmable interval timer */
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50 | #define PIT_CH0 0x40 |
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51 | #define PIT_CTRL 0x43 |
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52 | |||
53 | /*
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54 | * Clock interrupt service routine.
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55 | * No H/W reprogram is required.
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56 | */
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57 | static int |
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58 | clock_isr(void *arg)
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59 | { |
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60 | int s;
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61 | |||
62 | s = splhigh(); |
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63 | timer_handler(); |
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64 | splx(s); |
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65 | |||
66 | return INT_DONE;
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67 | } |
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68 | |||
69 | /*
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70 | * Initialize clock H/W chip.
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71 | * Setup clock tick rate and install clock ISR.
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72 | */
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73 | void
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74 | clock_init(void)
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75 | { |
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76 | irq_t clock_irq; |
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77 | |||
78 | outb_p(PIT_CTRL, 0x34); /* Command to set generator mode */ |
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79 | outb_p(PIT_CH0, (u_char)(PIT_LATCH & 0xff)); /* LSB */ |
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80 | outb_p(PIT_CH0, (u_char)((PIT_LATCH >> 8) & 0xff)); /* MSB */ |
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81 | |||
82 | clock_irq = irq_attach(CLOCK_IRQ, IPL_CLOCK, 0, &clock_isr,
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83 | IST_NONE, NULL);
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84 | |||
85 | DPRINTF(("Clock rate: %d ticks/sec\n", CONFIG_HZ));
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86 | } |