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Annotation of XNU/pexpert/ppc/pe_clock_speed.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
        !             3:  *
        !             4:  * @APPLE_LICENSE_HEADER_START@
        !             5:  * 
        !             6:  * The contents of this file constitute Original Code as defined in and
        !             7:  * are subject to the Apple Public Source License Version 1.1 (the
        !             8:  * "License").  You may not use this file except in compliance with the
        !             9:  * License.  Please obtain a copy of the License at
        !            10:  * http://www.apple.com/publicsource and read it before using this file.
        !            11:  * 
        !            12:  * This Original Code and all software distributed under the License are
        !            13:  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
        !            14:  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
        !            15:  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
        !            16:  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
        !            17:  * License for the specific language governing rights and limitations
        !            18:  * under the License.
        !            19:  * 
        !            20:  * @APPLE_LICENSE_HEADER_END@
        !            21:  */
        !            22: /*
        !            23:  *  clock_speed.c - Determine the best guess for the processor and bus
        !            24:  *                  speed buy using the values returned by run_clock_test.
        !            25:  *
        !            26:  *  (c) Apple Computer, Inc. 1998-9
        !            27:  *
        !            28:  *  Writen by:   Josh de Cesare
        !            29:  *
        !            30:  */
        !            31: 
        !            32: 
        !            33: #include <ppc/machine_routines.h>
        !            34: 
        !            35: #include <pexpert/ppc/powermac.h>
        !            36: 
        !            37: // prototypes
        !            38: extern void pe_run_clock_test(void *tmp);
        !            39: void pe_do_clock_test(unsigned int via_addr,
        !            40:                      int num_speeds, unsigned long *speed_list);
        !            41: 
        !            42: // Threshold for bus speed matches.
        !            43: #define kMaxFreqDiff  (30000)
        !            44: 
        !            45: // This is the structure for the data that get passed to pe_run_clock_test.
        !            46: struct clock_test_data {
        !            47:   unsigned int via_addr;
        !            48:   unsigned int via_ticks;
        !            49:   unsigned int dec_ticks;
        !            50: };
        !            51: 
        !            52: // glocal variables to simplify some stuff.
        !            53: static long bus_freq_num, bus_freq_den, cpu_pll;
        !            54: 
        !            55: // PE_Determine_Clock_Speeds is called by the via driver in IOKit
        !            56: // It uses the numbers generated by pe_do_clock_test and reports
        !            57: // the cleaned up values to the rest of the OS.
        !            58: void PE_Determine_Clock_Speeds(unsigned int via_addr, int num_speeds,
        !            59:                               unsigned long *speed_list)
        !            60: {
        !            61:   boolean_t oldLevel;
        !            62:   
        !            63:   oldLevel = ml_set_interrupts_enabled(FALSE);
        !            64:   pe_do_clock_test(via_addr, num_speeds, speed_list);
        !            65:   ml_set_interrupts_enabled(oldLevel);
        !            66:   
        !            67:   // Report the bus clock rate as is.
        !            68:   powermac_info.bus_clock_rate_num = bus_freq_num;
        !            69:   powermac_info.bus_clock_rate_den = bus_freq_den;
        !            70:   
        !            71:   // pll multipliers are in halfs so set the denominator to 2.
        !            72:   powermac_info.bus_to_cpu_rate_num = cpu_pll;
        !            73:   powermac_info.bus_to_cpu_rate_den = 2;
        !            74:   
        !            75:   // The decrementer rate is one fourth the bus rate.
        !            76:   powermac_info.bus_to_dec_rate_num = 1;
        !            77:   powermac_info.bus_to_dec_rate_den = 4;
        !            78:   
        !            79:   PE_call_timebase_callback();
        !            80: }
        !            81: 
        !            82: // pe_do_clock_test uses the number from pe_run_clock_test to
        !            83: // find a best fit guess for the bus speed.
        !            84: void pe_do_clock_test(unsigned int via_addr,
        !            85:                      int num_speeds, unsigned long *speed_list)
        !            86: {
        !            87:   struct clock_test_data clock_test_data;
        !            88:   long cnt, diff, raw_cpu_freq, raw_bus_freq, tmp_bus_freq,
        !            89:     last_bus_freq, tries = 10;
        !            90:   
        !            91:   // Save the via addr so the asm part can use it.
        !            92:   clock_test_data.via_addr = via_addr;
        !            93:   
        !            94:   // Keep looping until it matches the last try.
        !            95:   bus_freq_num = 0;
        !            96:   do {
        !            97:     last_bus_freq = bus_freq_num;
        !            98:     
        !            99:     // The the asm part to do the real work.
        !           100:     pe_run_clock_test((void *)&clock_test_data);
        !           101:     
        !           102:     // First find the pll mode.  Allow any integer times two.
        !           103:     cpu_pll = 10000000 / clock_test_data.dec_ticks;
        !           104:     cpu_pll = (cpu_pll / 2) + (cpu_pll & 1);
        !           105:     
        !           106:     // Using 64 bit math figure out the raw bus speed.
        !           107:     // 0xBF401675E5DULL is 1 / 1.27655us times 2 ^ 24.
        !           108:     raw_bus_freq = ((0xBF401675E5DULL * clock_test_data.dec_ticks) /
        !           109:                    clock_test_data.via_ticks) >> 22;
        !           110:     
        !           111:     // use the pll mode and the raw bus speed to find the raw cpu speed.
        !           112:     raw_cpu_freq = raw_bus_freq * cpu_pll / 2;
        !           113:     
        !           114:     // Look to see if the bus speed is close to one of the
        !           115:     // speeds in the table.
        !           116:     for (cnt = 0; cnt < num_speeds; cnt++) {
        !           117:       bus_freq_num = speed_list[cnt * 2];
        !           118:       bus_freq_den = speed_list[cnt * 2 + 1];
        !           119:       diff = bus_freq_num - raw_bus_freq * bus_freq_den;
        !           120:       if (diff < 0) diff = -diff;
        !           121:       
        !           122:       if (diff < kMaxFreqDiff * bus_freq_den) break;
        !           123:     }
        !           124:     if (cnt != num_speeds) continue;
        !           125:     
        !           126:     // Look to see if the bus speed is close to n * 0.5 MHz
        !           127:     tmp_bus_freq = ((raw_bus_freq + 250000) / 500000) * 500000;
        !           128:     
        !           129:     diff = tmp_bus_freq - raw_bus_freq;
        !           130:     if (diff < 0) diff = -diff;
        !           131:     
        !           132:     if (diff < kMaxFreqDiff) {
        !           133:       bus_freq_num = tmp_bus_freq;
        !           134:       bus_freq_den = 1;
        !           135:       continue;
        !           136:     }
        !           137:     
        !           138:     // Look to see if the bus speed is close to n * 50/3 MHz
        !           139:     tmp_bus_freq = ((raw_bus_freq * 3 + 25000000) / 50000000) * 50000000;
        !           140:     
        !           141:     diff = tmp_bus_freq - raw_bus_freq * 3;
        !           142:     if (diff < 0) diff = -diff;
        !           143:     
        !           144:     if (diff < kMaxFreqDiff * 3) {
        !           145:       bus_freq_num = tmp_bus_freq;
        !           146:       bus_freq_den = 3;
        !           147:       continue;
        !           148:     }
        !           149:     
        !           150:     // Since all else failed return the raw bus speed
        !           151:     bus_freq_num = raw_bus_freq;
        !           152:     bus_freq_den = 1;
        !           153:   } while ((bus_freq_num != last_bus_freq) && tries--);
        !           154: }

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