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1 /* File "FastTimes.c" - Original code by Matt Slot <fprefect@ambrosiasw.com> */
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2 /* Created 4/24/99 - This file is hereby placed in the public domain */
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3 /* Updated 5/21/99 - Calibrate to VIA, add TBR support, renamed functions */
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4 /* Updated 10/4/99 - Use AbsoluteToNanoseconds() in case Absolute = double */
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5 /* Updated 2/15/00 - Check for native Time Manager, no need to calibrate */
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6 /* Updated 2/19/00 - Fixed default value for gScale under native Time Mgr */
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7 /* Updated 3/21/00 - Fixed ns conversion, create 2 different scale factors */
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8 /* Updated 5/03/00 - Added copyright and placed into PD. No code changes */
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9 /* Updated 8/01/00 - Made "Carbon-compatible" by replacing LMGetTicks() */
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10
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11 /* This file is Copyright (C) Matt Slot, 1999-2000. It is hereby placed into
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12 the public domain. The author makes no warranty as to fitness or stability */
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13
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14 #include <Gestalt.h>
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15 #include <LowMem.h>
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16 #include <CodeFragments.h>
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17 #include <DriverServices.h>
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18 #include <Timer.h>
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19
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20 #include "FastTimes.h"
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21
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1659
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22 #ifdef TARGET_CPU_PPC
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23 #undef GENERATINGPOWERPC /* stop whining */
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24 #define GENERATINGPOWERPC TARGET_CPU_PPC
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25 #endif
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26
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27 /* **** **** **** **** **** **** **** **** **** **** **** **** **** **** **** */
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28 /* **** **** **** **** **** **** **** **** **** **** **** **** **** **** **** */
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29 /*
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30 On 680x0 machines, we just use Microseconds().
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31
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32 On PowerPC machines, we try several methods:
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33 * DriverServicesLib is available on all PCI PowerMacs, and perhaps
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34 some NuBus PowerMacs. If it is, we use UpTime() : Overhead = 2.1 µsec.
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35 * The PowerPC 601 has a built-in "real time clock" RTC, and we fall
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36 back to that, accessing it directly from asm. Overhead = 1.3 µsec.
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37 * Later PowerPCs have an accurate "time base register" TBR, and we
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38 fall back to that, access it from PowerPC asm. Overhead = 1.3 µsec.
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39 * We can also try Microseconds() which is emulated : Overhead = 36 µsec.
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40
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41 On PowerPC machines, we avoid the following:
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42 * OpenTransport is available on all PCI and some NuBus PowerMacs, but it
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43 uses UpTime() if available and falls back to Microseconds() otherwise.
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44 * InputSprocket is available on many PowerMacs, but again it uses
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45 UpTime() if available and falls back to Microseconds() otherwise.
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46
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47 Another PowerPC note: certain configurations, especially 3rd party upgrade
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48 cards, may return inaccurate timings for the CPU or memory bus -- causing
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49 skew in various system routines (up to 20% drift!). The VIA chip is very
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50 accurate, and it's the basis for the Time Manager and Microseconds().
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51 Unfortunately, it's also very slow because the MacOS has to (a) switch to
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52 68K and (b) poll for a VIA event.
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53
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54 We compensate for the drift by calibrating a floating point scale factor
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55 between our fast method and the accurate timer at startup, then convert
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56 each sample quickly on the fly. I'd rather not have the initialization
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57 overhead -- but it's simply necessary for accurate timing. You can drop
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58 it down to 30 ticks if you prefer, but that's as low as I'd recommend.
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59
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60 Under MacOS 9, "new world" Macs (iMacs, B+W G3s and G+W G4s) have a native
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61 Time Manager implementation: UpTime(), Microseconds(), and TickCount() are
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62 all based on the same underlying counter. This makes it silly to calibrate
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63 UpTime() against TickCount(). We now check for this feature using Gestalt(),
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64 and skip the whole calibration step if possible.
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65
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66 */
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67 /* **** **** **** **** **** **** **** **** **** **** **** **** **** **** **** */
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68 /* **** **** **** **** **** **** **** **** **** **** **** **** **** **** **** */
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69
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70 #define RTCToNano(w) ((double) (w).hi * 1000000000.0 + (double) (w).lo)
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71 #define WideTo64bit(w) (*(UInt64 *) &(w))
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72
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73 /* LMGetTicks() is not in Carbon and TickCount() has a fair bit of overhead,
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74 so for speed we always read lowmem directly. This is a Mac OS X no-no, but
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75 it always work on those systems that don't have a native Time Manager (ie,
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76 anything before MacOS 9) -- regardless whether we are in Carbon or not! */
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77 #define MyLMGetTicks() (*(volatile UInt32 *) 0x16A)
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78
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79 #if GENERATINGPOWERPC
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80
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81 static asm UnsignedWide PollRTC(void);
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82 static asm UnsignedWide PollTBR(void);
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83 static Ptr FindFunctionInSharedLib(StringPtr libName, StringPtr funcName);
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84
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85 static Boolean gInited = false;
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86 static Boolean gNative = false;
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87 static Boolean gUseRTC = false;
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88 static Boolean gUseTBR = false;
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89 static double gScaleUSec = 1.0 / 1000.0; /* 1 / ( nsec / usec) */
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90 static double gScaleMSec = 1.0 / 1000000.0; /* 1 / ( nsec / msec) */
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91
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92 /* Functions loaded from DriverServicesLib */
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93 typedef AbsoluteTime (*UpTimeProcPtr)(void);
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94 typedef Nanoseconds (*A2NSProcPtr)(AbsoluteTime);
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95 static UpTimeProcPtr gUpTime = NULL;
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96 static A2NSProcPtr gA2NS = NULL;
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97
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98 #endif /* GENERATINGPOWERPC */
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99
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100 /* **** **** **** **** **** **** **** **** **** **** **** **** **** **** **** */
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101 /* **** **** **** **** **** **** **** **** **** **** **** **** **** **** **** */
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102
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103 void FastInitialize() {
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104 SInt32 result;
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105
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106 if (!gInited) {
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107
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108 #if GENERATINGPOWERPC
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109
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110 /* Initialize the feature flags */
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111 gNative = gUseRTC = gUseTBR = false;
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112
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113 /* We use CFM to find and load needed symbols from shared libraries, so
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114 the application doesn't have to weak-link them, for convenience. */
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115 gUpTime = (UpTimeProcPtr) FindFunctionInSharedLib(
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116 "\pDriverServicesLib", "\pUpTime");
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117 if (gUpTime) gA2NS = (A2NSProcPtr) FindFunctionInSharedLib(
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118 "\pDriverServicesLib", "\pAbsoluteToNanoseconds");
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119 if (!gA2NS) gUpTime = nil; /* Pedantic but necessary */
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120
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121 if (gUpTime) {
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122 /* If we loaded UpTime(), then we need to know if the system has
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123 a native implementation of the Time Manager. If so, then it's
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124 pointless to calculate a scale factor against the missing VIA */
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125
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126 /* gestaltNativeTimeMgr = 4 in some future version of the headers */
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127 if (!Gestalt(gestaltTimeMgrVersion, &result) &&
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128 (result > gestaltExtendedTimeMgr))
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129 gNative = true;
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130 }
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131 else {
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132 /* If no DriverServicesLib, use Gestalt() to get the processor type.
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133 Only NuBus PowerMacs with old System Software won't have DSL, so
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134 we know it should either be a 601 or 603. */
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135
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136 /* Use the processor gestalt to determine which register to use */
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137 if (!Gestalt(gestaltNativeCPUtype, &result)) {
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138 if (result == gestaltCPU601) gUseRTC = true;
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139 else if (result > gestaltCPU601) gUseTBR = true;
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140 }
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141 }
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142
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143 /* Now calculate a scale factor to keep us accurate. */
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144 if ((gUpTime && !gNative) || gUseRTC || gUseTBR) {
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145 UInt64 tick, usec1, usec2;
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146 UnsignedWide wide;
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147
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148 /* Wait for the beginning of the very next tick */
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149 for(tick = MyLMGetTicks() + 1; tick > MyLMGetTicks(); );
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150
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151 /* Poll the selected timer and prepare it (since we have time) */
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152 wide = (gUpTime) ? (*gA2NS)((*gUpTime)()) :
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153 ((gUseRTC) ? PollRTC() : PollTBR());
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154 usec1 = (gUseRTC) ? RTCToNano(wide) : WideTo64bit(wide);
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155
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156 /* Wait for the exact 60th tick to roll over */
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157 while(tick + 60 > MyLMGetTicks());
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158
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159 /* Poll the selected timer again and prepare it */
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160 wide = (gUpTime) ? (*gA2NS)((*gUpTime)()) :
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161 ((gUseRTC) ? PollRTC() : PollTBR());
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162 usec2 = (gUseRTC) ? RTCToNano(wide) : WideTo64bit(wide);
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163
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164 /* Calculate a scale value that will give microseconds per second.
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165 Remember, there are actually 60.15 ticks in a second, not 60. */
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166 gScaleUSec = (60.0 * 1000000.0) / ((usec2 - usec1) * 60.15);
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167 gScaleMSec = gScaleUSec / 1000.0;
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168 }
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169
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170 #endif /* GENERATINGPOWERPC */
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171
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172 /* We've initialized our globals */
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173 gInited = true;
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174 }
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175 }
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176
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177 /* **** **** **** **** **** **** **** **** **** **** **** **** **** **** **** */
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178 /* **** **** **** **** **** **** **** **** **** **** **** **** **** **** **** */
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179
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180 UInt64 FastMicroseconds() {
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181 UnsignedWide wide;
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182 UInt64 usec;
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183
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184 #if GENERATINGPOWERPC
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185 /* Initialize globals the first time we are called */
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186 if (!gInited) FastInitialize();
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187
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188 if (gNative) {
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189 /* Use DriverServices if it's available -- it's fast and compatible */
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190 wide = (*gA2NS)((*gUpTime)());
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191 usec = (double) WideTo64bit(wide) * gScaleUSec + 0.5;
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192 }
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193 else if (gUpTime) {
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194 /* Use DriverServices if it's available -- it's fast and compatible */
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195 wide = (*gA2NS)((*gUpTime)());
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196 usec = (double) WideTo64bit(wide) * gScaleUSec + 0.5;
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197 }
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198 else if (gUseTBR) {
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199 /* On a recent PowerPC, we poll the TBR directly */
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200 wide = PollTBR();
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201 usec = (double) WideTo64bit(wide) * gScaleUSec + 0.5;
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202 }
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203 else if (gUseRTC) {
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204 /* On a 601, we can poll the RTC instead */
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205 wide = PollRTC();
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206 usec = (double) RTCToNano(wide) * gScaleUSec + 0.5;
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207 }
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208 else
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209 #endif /* GENERATINGPOWERPC */
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210 {
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211 /* If all else fails, suffer the mixed mode overhead */
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212 Microseconds(&wide);
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213 usec = WideTo64bit(wide);
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214 }
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215
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216 return(usec);
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217 }
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218
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219 /* **** **** **** **** **** **** **** **** **** **** **** **** **** **** **** */
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220 /* **** **** **** **** **** **** **** **** **** **** **** **** **** **** **** */
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221
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222 UInt64 FastMilliseconds() {
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223 UnsignedWide wide;
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224 UInt64 msec;
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225
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226 #if GENERATINGPOWERPC
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227 /* Initialize globals the first time we are called */
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228 if (!gInited) FastInitialize();
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229
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230 if (gNative) {
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231 /* Use DriverServices if it's available -- it's fast and compatible */
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232 wide = (*gA2NS)((*gUpTime)());
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233 msec = (double) WideTo64bit(wide) * gScaleMSec + 0.5;
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234 }
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235 else if (gUpTime) {
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236 /* Use DriverServices if it's available -- it's fast and compatible */
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237 wide = (*gA2NS)((*gUpTime)());
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238 msec = (double) WideTo64bit(wide) * gScaleMSec + 0.5;
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239 }
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240 else if (gUseTBR) {
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241 /* On a recent PowerPC, we poll the TBR directly */
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242 wide = PollTBR();
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243 msec = (double) WideTo64bit(wide) * gScaleMSec + 0.5;
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244 }
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245 else if (gUseRTC) {
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246 /* On a 601, we can poll the RTC instead */
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247 wide = PollRTC();
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248 msec = (double) RTCToNano(wide) * gScaleMSec + 0.5;
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249 }
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250 else
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251 #endif /* GENERATINGPOWERPC */
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252 {
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253 /* If all else fails, suffer the mixed mode overhead */
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254 Microseconds(&wide);
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255 msec = ((double) WideTo64bit(wide) + 500.0) / 1000.0;
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256 }
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257
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258 return(msec);
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259 }
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260
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261 /* **** **** **** **** **** **** **** **** **** **** **** **** **** **** **** */
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262 /* **** **** **** **** **** **** **** **** **** **** **** **** **** **** **** */
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263
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264 StringPtr FastMethod() {
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265 StringPtr method = "\p<Unknown>";
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266
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267 #if GENERATINGPOWERPC
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268 /* Initialize globals the first time we are called */
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269 if (!gInited) FastInitialize();
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270
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271 if (gNative) {
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272 /* The Time Manager and UpTime() are entirely native on this machine */
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273 method = "\pNative UpTime()";
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274 }
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275 else if (gUpTime) {
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276 /* Use DriverServices if it's available -- it's fast and compatible */
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277 method = "\pUpTime()";
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278 }
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279 else if (gUseTBR) {
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280 /* On a recent PowerPC, we poll the TBR directly */
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281 method = "\pPowerPC TBR";
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282 }
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283 else if (gUseRTC) {
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284 /* On a 601, we can poll the RTC instead */
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285 method = "\pPowerPC RTC";
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286 }
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287 else
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288 #endif /* GENERATINGPOWERPC */
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289 {
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290 /* If all else fails, suffer the mixed mode overhead */
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291 method = "\pMicroseconds()";
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292 }
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293
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294 return(method);
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295 }
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296
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297 /* **** **** **** **** **** **** **** **** **** **** **** **** **** **** **** */
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298 /* **** **** **** **** **** **** **** **** **** **** **** **** **** **** **** */
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299 #pragma mark -
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300
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301 #if GENERATINGPOWERPC
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302 asm static UnsignedWide PollRTC_() {
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303 entry PollRTC /* Avoid CodeWarrior glue */
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304 machine 601
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305 @AGAIN:
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306 mfrtcu r4 /* RTCU = SPR 4 */
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307 mfrtcl r5 /* RTCL = SPR 5 */
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308 mfrtcu r6
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309 cmpw r4,r6
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310 bne @AGAIN
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311 stw r4,0(r3)
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312 stw r5,4(r3)
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313 blr
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314 }
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315
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316 /* **** **** **** **** **** **** **** **** **** **** **** **** **** **** **** */
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317 /* **** **** **** **** **** **** **** **** **** **** **** **** **** **** **** */
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318
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319 asm static UnsignedWide PollTBR_() {
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320 entry PollTBR /* Avoid CodeWarrior glue */
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321 machine 604
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322 @AGAIN:
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323 mftbu r4 /* TBRU = SPR 268 */
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324 mftb r5 /* TBRL = SPR 269 */
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325 mftbu r6
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326 cmpw r4,r6
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327 bne @AGAIN
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328 stw r4,0(r3)
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329 stw r5,4(r3)
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330 blr
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331 }
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332
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333 /* **** **** **** **** **** **** **** **** **** **** **** **** **** **** **** */
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334 /* **** **** **** **** **** **** **** **** **** **** **** **** **** **** **** */
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335
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336 static Ptr FindFunctionInSharedLib(StringPtr libName, StringPtr funcName) {
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337 OSErr error = noErr;
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338 Str255 errorStr;
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339 Ptr func = NULL;
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340 Ptr entry = NULL;
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341 CFragSymbolClass symClass;
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342 CFragConnectionID connID;
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343
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344 /* Find CFM containers for the current archecture -- CFM-PPC or CFM-68K */
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345 if (/* error = */ GetSharedLibrary(libName, kCompiledCFragArch,
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346 kLoadCFrag, &connID, &entry, errorStr)) return(NULL);
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347 if (/* error = */ FindSymbol(connID, funcName, &func, &symClass))
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348 return(NULL);
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349
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350 return(func);
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351 }
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352 #endif /* GENERATINGPOWERPC */
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