1 | /* Timer_init() |
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2 | * |
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3 | * This routine initializes a timer in efi68k's DP8570A TCP |
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4 | * |
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5 | * Input parameters: NONE |
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6 | * |
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7 | * Output parameters: NONE |
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8 | * |
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9 | * NOTE: It is important that the timer start/stop overhead be |
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10 | * determined when porting or modifying this code. |
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11 | * |
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12 | * COPYRIGHT (c) 1989-1999. |
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13 | * On-Line Applications Research Corporation (OAR). |
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14 | * |
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15 | * The license and distribution terms for this file may be |
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16 | * found in the file LICENSE in this distribution or at |
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17 | * http://www.rtems.com/license/LICENSE. |
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18 | * |
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19 | * $Id$ |
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20 | */ |
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21 | |
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22 | |
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23 | #include <bsp.h> |
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24 | |
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25 | rtems_boolean Timer_driver_Find_average_overhead; |
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26 | |
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27 | extern rtems_isr Clock_isr(); |
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28 | |
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29 | void Timer_initialize( void ) |
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30 | { |
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31 | /* stop counter */ |
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32 | *MSR = 0; |
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33 | *T0CR = 0; |
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34 | |
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35 | /* |
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36 | * Make sure isr is installed |
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37 | */ |
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38 | |
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39 | set_vector( Clock_isr, TCP_ISR_LEVEL+24, 1); |
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40 | |
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41 | /* clear timer ISR count */ |
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42 | Timer_interrupts = 0; |
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43 | |
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44 | /* load count (count down timer) */ |
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45 | *MSR = 0; |
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46 | *T0_MSB = 0xff; |
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47 | *T0_LSB = 0xff; |
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48 | |
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49 | /* clear old interrupts */ |
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50 | *MSR = T0; |
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51 | |
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52 | /* enable timer 0 interrupt */ |
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53 | *MSR = RS; |
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54 | *ICR0 |= T0E; |
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55 | |
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56 | /* |
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57 | TSS = 1 starts the timer (timer resets on start) |
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58 | M1/0 = 0/1 rate generator |
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59 | C2/1/0 = 0/0/0 external clock (8MHz) (1/8 usec resolution) |
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60 | RD = 0 read data (latchs count) |
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61 | CHG = 0 hold |
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62 | */ |
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63 | *MSR = 0; |
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64 | *T0CR = (TSS | M0); |
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65 | } |
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66 | |
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67 | /* |
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68 | * The following controls the behavior of Read_timer(). |
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69 | * |
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70 | * FIND_AVG_OVERHEAD * instructs the routine to return the "raw" count. |
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71 | * |
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72 | * AVG_OVEREHAD is the overhead for starting and stopping the timer. It |
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73 | * is usually deducted from the number returned. |
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74 | * |
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75 | * LEAST_VALID is the lowest number this routine should trust. Numbers |
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76 | * below this are "noise" and zero is returned. |
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77 | */ |
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78 | |
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79 | #define AVG_OVERHEAD 0 /* It typically takes X.X microseconds */ |
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80 | /* (Y countdowns) to start/stop the timer. */ |
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81 | /* This value is in microseconds. */ |
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82 | #define LEAST_VALID 1 /* Don't trust a clicks value lower than this */ |
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83 | |
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84 | /* |
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85 | * Return timer value in 1/2-microsecond units |
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86 | */ |
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87 | int Read_timer( void ) |
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88 | { |
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89 | rtems_unsigned16 clicks; |
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90 | rtems_unsigned32 total; |
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91 | rtems_unsigned32 msb, lsb; |
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92 | |
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93 | |
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94 | /* |
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95 | * Read the timer and see how many clicks it has been since counter |
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96 | * rolled over. |
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97 | */ |
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98 | |
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99 | *MSR = 0; |
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100 | *T0CR |= RD; |
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101 | /* must read MSB first */ |
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102 | msb = *T0_MSB; |
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103 | lsb = *T0_LSB; |
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104 | clicks = 0xffff - ((msb << 8) | lsb); |
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105 | |
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106 | /* |
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107 | * Total is calculated by taking into account the number of timer overflow |
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108 | * interrupts since the timer was initialized and clicks since the last |
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109 | * interrupts. |
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110 | */ |
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111 | |
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112 | total = (Timer_interrupts * 0x10000 + clicks + 4)/8; /* in micoseconds */ |
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113 | /* ^^^ round to nearest int */ |
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114 | |
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115 | if ( Timer_driver_Find_average_overhead == 1 ) |
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116 | return total; /* in XXX microsecond units */ |
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117 | |
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118 | if ( total < LEAST_VALID ) |
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119 | return 0; /* below timer resolution */ |
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120 | |
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121 | return (total - AVG_OVERHEAD); |
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122 | } |
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123 | |
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124 | |
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125 | /* |
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126 | * Empty function call used in loops to measure basic cost of looping |
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127 | * in Timing Test Suite. |
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128 | */ |
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129 | |
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130 | rtems_status_code Empty_function(void) |
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131 | { |
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132 | return RTEMS_SUCCESSFUL; |
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133 | } |
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134 | |
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135 | void Set_find_average_overhead( |
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136 | rtems_boolean find_flag |
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137 | ) |
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138 | { |
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139 | Timer_driver_Find_average_overhead = find_flag; |
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140 | } |
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