Rev 4418 | Details | Compare with Previous | Last modification | View Log | RSS feed
Rev | Author | Line No. | Line |
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3520 | clevermous | 1 | ; Implementation of periodic transaction scheduler for USB. |
2 | ; Bandwidth dedicated to periodic transactions is limited, so |
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3 | ; different pipes should be scheduled as uniformly as possible. |
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4 | |||
5 | ; USB1 scheduler. |
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6 | ; Algorithm is simple: |
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7 | ; when adding a pipe, optimize the following quantity: |
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8 | ; * for every millisecond, take all bandwidth scheduled to periodic transfers, |
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9 | ; * calculate maximum over all milliseconds, |
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10 | ; * select a variant which minimizes that maximum; |
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11 | ; when removing a pipe, do nothing (except for bookkeeping). |
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12 | |||
4418 | clevermous | 13 | ; The caller must provide CONTROLLER_NAME define. |
14 | macro define_controller_name name |
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15 | { |
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16 | _hci_static_ep.SoftwarePart = name # _static_ep.SoftwarePart |
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17 | _hci_static_ep.NextList = name # _static_ep.NextList |
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18 | sizeof._hci_static_ep = sizeof. # name # _static_ep |
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19 | } |
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20 | |||
3520 | clevermous | 21 | ; Select a list for a new pipe. |
22 | ; in: esi -> usb_controller, maxpacket, type, interval can be found in the stack |
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23 | ; in: ecx = 2 * maximal interval = total number of periodic lists + 1 |
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24 | ; in: edx -> {u|o}hci_static_ep for the first list |
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25 | ; in: eax -> byte past {u|o}hci_static_ep for the last list in the first group |
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26 | ; out: edx -> usb_static_ep for the selected list or zero if failed |
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27 | proc usb1_select_interrupt_list |
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28 | ; inherit some variables from usb_open_pipe |
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3816 | clevermous | 29 | virtual at ebp-12 |
30 | .speed db ? |
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31 | rb 3 |
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3520 | clevermous | 32 | .bandwidth dd ? |
33 | .target dd ? |
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34 | dd ? |
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35 | dd ? |
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36 | .config_pipe dd ? |
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37 | .endpoint dd ? |
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38 | .maxpacket dd ? |
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39 | .type dd ? |
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40 | .interval dd ? |
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41 | end virtual |
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42 | push ebx edi ; save used registers to be stdcall |
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43 | push eax ; save eax for checks in step 3 |
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44 | ; 1. Only intervals 2^k ms can be supported. |
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45 | ; The core specification says that the real interval should not be greater |
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46 | ; than the interval given by the endpoint descriptor, but can be less. |
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47 | ; Determine the actual interval as 2^k ms. |
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48 | mov eax, ecx |
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49 | ; 1a. Set [.interval] to 1 if it was zero; leave it as is otherwise |
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50 | cmp [.interval], 1 |
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51 | adc [.interval], 0 |
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52 | ; 1b. Divide ecx by two while it is strictly greater than [.interval]. |
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53 | @@: |
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54 | shr ecx, 1 |
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55 | cmp [.interval], ecx |
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56 | jb @b |
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57 | ; ecx = the actual interval |
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58 | ; |
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59 | ; For example, let ecx = 8, eax = 64. |
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60 | ; The scheduler space is 32 milliseconds, |
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61 | ; we need to schedule something every 8 ms; |
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62 | ; there are 8 variants: schedule at times 0,8,16,24, |
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63 | ; schedule at times 1,9,17,25,..., schedule at times 7,15,23,31. |
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64 | ; Now concentrate: there are three nested loops, |
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65 | ; * the innermost loop calculates the total periodic bandwidth scheduled |
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66 | ; in the given millisecond, |
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67 | ; * the intermediate loop calculates the maximum over all milliseconds |
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68 | ; in the given variant, that is the quantity we're trying to minimize, |
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69 | ; * the outermost loop checks all variants. |
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70 | ; 2. Calculate offset between the first list and the first list for the |
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71 | ; selected interval, in bytes; save in the stack for step 4. |
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72 | sub eax, ecx |
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73 | sub eax, ecx |
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4418 | clevermous | 74 | imul eax, sizeof._hci_static_ep |
3520 | clevermous | 75 | push eax |
4418 | clevermous | 76 | imul ebx, ecx, sizeof._hci_static_ep |
3520 | clevermous | 77 | ; 3. Select the best variant. |
78 | ; 3a. The outermost loop. |
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79 | ; Prepare for the loop: set the current optimal bandwidth to maximum |
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80 | ; possible value (so that any variant will pass the first comparison), |
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81 | ; calculate delta for the intermediate loop. |
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82 | or [.bandwidth], -1 |
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83 | .varloop: |
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84 | ; 3b. The intermediate loop. |
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85 | ; Prepare for the loop: set the maximum to be calculated to zero, |
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86 | ; save counter of the outermost loop. |
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87 | xor edi, edi |
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88 | push edx |
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89 | virtual at esp |
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90 | .cur_variant dd ? ; step 3b |
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91 | .result_delta dd ? ; step 2 |
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92 | .group1_limit dd ? ; function prolog |
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93 | end virtual |
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94 | .calc_max_bandwidth: |
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95 | ; 3c. The innermost loop. Sum over all lists. |
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96 | xor eax, eax |
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97 | push edx |
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98 | .calc_bandwidth: |
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4418 | clevermous | 99 | add eax, [edx+_hci_static_ep.SoftwarePart+usb_static_ep.Bandwidth] |
100 | mov edx, [edx+_hci_static_ep.NextList] |
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3520 | clevermous | 101 | test edx, edx |
102 | jnz .calc_bandwidth |
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103 | pop edx |
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104 | ; 3d. The intermediate loop continued: update maximum. |
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105 | cmp eax, edi |
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106 | jb @f |
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107 | mov edi, eax |
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108 | @@: |
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109 | ; 3e. The intermediate loop continued: advance counter. |
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110 | add edx, ebx |
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111 | cmp edx, [.group1_limit] |
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112 | jb .calc_max_bandwidth |
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113 | ; 3e. The intermediate loop done: restore counter of the outermost loop. |
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114 | pop edx |
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115 | ; 3f. The outermost loop continued: if the current variant is |
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116 | ; better (maybe not strictly) then the previous optimum, update |
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117 | ; the optimal bandwidth and resulting list. |
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118 | cmp edi, [.bandwidth] |
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119 | ja @f |
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120 | mov [.bandwidth], edi |
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121 | mov [.target], edx |
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122 | @@: |
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123 | ; 3g. The outermost loop continued: advance counter. |
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4418 | clevermous | 124 | add edx, sizeof._hci_static_ep |
3520 | clevermous | 125 | dec ecx |
126 | jnz .varloop |
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3816 | clevermous | 127 | ; 4. Calculate bandwidth for the new pipe. |
128 | mov eax, [.maxpacket] |
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129 | mov cl, [.speed] |
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130 | mov ch, byte [.endpoint] |
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131 | and ch, 80h |
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132 | call calc_usb1_bandwidth |
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133 | ; 5. Get the pointer to the best list. |
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3520 | clevermous | 134 | pop edx ; restore value from step 2 |
3816 | clevermous | 135 | pop ecx ; purge stack var from prolog |
3520 | clevermous | 136 | add edx, [.target] |
3816 | clevermous | 137 | ; 6. Check that bandwidth for the new pipe plus old bandwidth |
138 | ; still fits to maximum allowed by the core specification, 90% of 12000 bits. |
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139 | mov ecx, eax |
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140 | add ecx, [.bandwidth] |
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141 | cmp ecx, 10800 |
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142 | ja .no_bandwidth |
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3520 | clevermous | 143 | ; 7. Convert {o|u}hci_static_ep to usb_static_ep, update bandwidth and return. |
4418 | clevermous | 144 | add edx, _hci_static_ep.SoftwarePart |
3520 | clevermous | 145 | add [edx+usb_static_ep.Bandwidth], eax |
146 | pop edi ebx ; restore used registers to be stdcall |
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147 | ret |
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3816 | clevermous | 148 | .no_bandwidth: |
149 | dbgstr 'Periodic bandwidth limit reached' |
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150 | xor edx, edx |
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151 | pop edi ebx |
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152 | ret |
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3520 | clevermous | 153 | endp |
154 | |||
155 | ; Pipe is removing, update the corresponding lists. |
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156 | ; We do not reorder anything, so just update book-keeping variable |
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157 | ; in the list header. |
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158 | proc usb1_interrupt_list_unlink |
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159 | virtual at esp |
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160 | dd ? ; return address |
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161 | .maxpacket dd ? |
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162 | .lowspeed db ? |
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163 | .direction db ? |
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164 | rb 2 |
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165 | end virtual |
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3816 | clevermous | 166 | ; calculate bandwidth on the bus |
167 | mov eax, [.maxpacket] |
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168 | mov ecx, dword [.lowspeed] |
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169 | call calc_usb1_bandwidth |
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4547 | clevermous | 170 | mov edx, [ebx+usb_pipe.BaseList] |
3520 | clevermous | 171 | ; subtract pipe bandwidth |
172 | sub [edx+usb_static_ep.Bandwidth], eax |
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173 | ret 8 |
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174 | endp |
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175 | |||
3816 | clevermous | 176 | ; Helper procedure for USB1 scheduler: calculate bandwidth on the bus. |
177 | ; in: low 11 bits of eax = payload size in bytes |
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178 | ; in: cl = 0 - full-speed, nonzero - high-speed |
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179 | ; in: ch = 0 - OUT, nonzero - IN |
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180 | ; out: eax = maximal bandwidth in FS-bits |
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181 | proc calc_usb1_bandwidth |
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182 | and eax, (1 shl 11) - 1 ; get payload for one transaction |
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183 | add eax, 3 ; add 3 bytes for other fields in data packet, PID+CRC16 |
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184 | test cl, cl |
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185 | jnz .low_speed |
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186 | ; Multiply by 8 for bytes -> bits, by 7/6 to accomodate bit stuffing |
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187 | ; and by 401/400 for IN transfers to accomodate timers difference |
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188 | ; 9+107/300 for IN transfers, 9+1/3 for OUT transfers |
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189 | ; For 0 <= eax < 09249355h, floor(eax * 107/300) = floor(eax * 5B4E81B5h / 2^32). |
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190 | ; For 0 <= eax < 80000000h, floor(eax / 3) = floor(eax * 55555556h / 2^32). |
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191 | mov edx, 55555556h |
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192 | test ch, ch |
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193 | jz @f |
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194 | mov edx, 5B4E81B5h |
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195 | @@: |
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196 | lea ecx, [eax*9] |
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197 | mul edx |
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198 | ; Add 93 extra bits: 39 bits for Token packet (8 for SYNC, 24 for token+address, |
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199 | ; 4 extra bits for possible bit stuffing in token+address, 3 for EOP), |
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200 | ; 18 bits for bus turn-around, 11 bits for SYNC+EOP in Data packet plus 1 bit |
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201 | ; for possible timers difference, 2 bits for inter-packet delay, 20 bits for |
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202 | ; Handshake packet, 2 bits for another inter-packet delay. |
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203 | lea eax, [ecx+edx+93] |
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204 | ret |
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205 | .low_speed: |
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206 | ; Multiply by 8 for bytes -> bits, by 7/6 to accomodate bit stuffing, |
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207 | ; by 8 for LS -> FS and by 406/50 for IN transfers to accomodate timers difference. |
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208 | ; 75+59/75 for IN transfers, 74+2/3 for OUT transfers. |
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209 | mov edx, 0AAAAAABh |
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210 | test ch, ch |
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211 | mov ecx, 74 |
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212 | jz @f |
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213 | mov edx, 0C962FC97h |
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214 | inc ecx |
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215 | @@: |
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216 | imul ecx, eax |
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217 | mul edx |
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218 | ; Add 778 extra bits: |
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219 | ; 16 bits for PRE packet, 4 bits for hub delay, 8*39 bits for Token packet |
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220 | ; 8*18 bits for bus turn-around |
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221 | ; (406/50)*11 bits for SYNC+EOP in Data packet, |
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222 | ; 8*2 bits for inter-packet delay, |
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223 | ; 16 bits for PRE packet, 4 bits for hub delay, 8*20 bits for Handshake packet, |
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224 | ; 8*2 bits for another inter-packet delay. |
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225 | lea eax, [ecx+edx+778] |
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226 | ret |
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227 | endp>=>>=> |