scoutos / prex-0.9.0 / bsp / hal / arm / gba / 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
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32 | */
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33 | |||
34 | #include <sys/ipl.h> |
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35 | #include <kernel.h> |
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36 | #include <timer.h> |
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37 | #include <irq.h> |
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38 | #include <cpufunc.h> |
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39 | |||
40 | |||
41 | /* Interrupt vector for timer (TMR0 of GBA) */
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42 | #define CLOCK_IRQ 3 |
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43 | |||
44 | /* The clock rate per second ... 2^24 */
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45 | #define CLOCK_RATE 16777216L |
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46 | |||
47 | /* The initial counter value */
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48 | #define TIMER_COUNT (0xffff - (CLOCK_RATE / 64 / HZ)) |
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49 | |||
50 | /* GBA timer registers */
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51 | #define TMR0_COUNT (*(volatile uint16_t *)0x4000100) |
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52 | #define TMR0_CTRL (*(volatile uint16_t *)0x4000102) |
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53 | |||
54 | /* Timer frequency */
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55 | #define TMR_1_CLOCK 0x0000 |
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56 | #define TMR_64_CLOCK 0x0001 |
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57 | #define TMR_256_CLOCK 0x0002 |
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58 | #define TMR_1024_CLOCK 0x0003 |
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59 | |||
60 | /* Cascade switch */
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61 | #define TMR_CASCADE 0x0004 |
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62 | |||
63 | /* Interrupt for overflow */
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64 | #define TMR_IRQEN 0x0040 |
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65 | |||
66 | /* Timer switch */
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67 | #define TMR_EN 0x0080 |
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68 | |||
69 | /*
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70 | * Clock interrupt service routine.
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71 | * No H/W reprogram is required.
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72 | */
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73 | static int |
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74 | clock_isr(void *arg)
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75 | { |
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76 | |||
77 | splhigh(); |
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78 | timer_handler(); |
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79 | spl0(); |
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80 | return INT_DONE;
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81 | } |
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82 | |||
83 | /*
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84 | * Initialize clock H/W chip.
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85 | * Setup clock tick rate and install clock ISR.
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86 | */
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87 | void
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88 | clock_init(void)
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89 | { |
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90 | irq_t clock_irq; |
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91 | |||
92 | /* Setup counter value */
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93 | TMR0_COUNT = TIMER_COUNT; |
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94 | TMR0_CTRL = (uint16_t)(TMR_IRQEN | TMR_64_CLOCK); |
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95 | |||
96 | /* Install ISR */
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97 | clock_irq = irq_attach(CLOCK_IRQ, IPL_CLOCK, 0, &clock_isr,
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98 | IST_NONE, NULL);
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99 | |||
100 | /* Enable timer */
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101 | TMR0_CTRL |= TMR_EN; |
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102 | } |