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Annotation of XNU/pexpert/ppc/pe_clock_speed_asm.s, 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_asm.s - Uses the Via timer, decrementer, and counter
        !            24:  *                     to determine the clock and bus rates.
        !            25:  *
        !            26:  *  (c) Apple Computer, Inc. 1998-9
        !            27:  *
        !            28:  *  Writen by:  Josh de Cesare
        !            29:  *
        !            30:  */
        !            31: 
        !            32: #include <ppc/asm.h>
        !            33: 
        !            34: // constants for the via
        !            35: #define CountLow  0x800
        !            36: #define CountHigh 0xa00
        !            37: #define LatchLow  0xc00
        !            38: #define LatchHigh 0xe00
        !            39: 
        !            40: 
        !            41: // void pe_run_clock_test(clock_test_data *data)
        !            42: //
        !            43: // data points to the base address of the via and two longs
        !            44: // for storing the via and dec results.
        !            45: //
        !            46: // The basic idea is this...
        !            47: // Use the counter register to execute a loop that will take
        !            48: // 10,000,000 processor clocks.  Time it using both the via counter
        !            49: // and the time base.  Return the number of ticks for both so the
        !            50: // raw values for processor and bus speed can be calculated.
        !            51: ENTRY(pe_run_clock_test, TAG_NO_FRAME_USED)
        !            52: 
        !            53:        li      r4,     1               ; flag for cache load
        !            54:        li      r5,     1               ; Only once through this time
        !            55:        lwz     r9,     0(r3)           ; r9 is the via addr
        !            56: 
        !            57: L_again:
        !            58:        mtctr   r5                      ; set the count
        !            59:        li      r5,     0xff            ; Start the counter at 0xffff
        !            60:        stb     r5,     CountLow(r9)    ; clear the via counter
        !            61:        eieio
        !            62:        stb     r5,     CountHigh(r9)
        !            63:        eieio
        !            64:        mftb    r10                     ; save starting value of the time base
        !            65:        isync
        !            66: 
        !            67: L_loop:
        !            68:        addi    r5,     r5,     1       ; 8 adds for 8 cycles
        !            69:        addi    r5,     r5,     2       ; the bdnz should be 0 cycles
        !            70:        addi    r5,     r5,     3
        !            71:        addi    r5,     r5,     4
        !            72:        addi    r5,     r5,     5
        !            73:        addi    r5,     r5,     6
        !            74:        addi    r5,     r5,     7
        !            75:        addi    r5,     r5,     8
        !            76:        bdnz    L_loop
        !            77: 
        !            78:        sync
        !            79:        mftb    r5                      ; save the raw time base value
        !            80:        lbz     r6,     CountHigh(r9)   ; get the via counter values
        !            81:        eieio
        !            82:        lbz     r7,     CountLow(r9)
        !            83:        eieio
        !            84:        lbz     r8,     CountHigh(r9)
        !            85:        eieio
        !            86: 
        !            87:        cmpi    cr0,    r4,     1       ; see if the was the cache run
        !            88:        bne     L_finish_up             ; nope, we are done.
        !            89: 
        !            90:        li      r4,     0               ; set flag for the real test
        !            91:        li      r5,     0x12d0          ; set the initial count to 1.25e+6
        !            92:        oris    r5,     r5,     0x13
        !            93:        b       L_again
        !            94: 
        !            95: L_finish_up:
        !            96:        cmpi    cr0,    r7,     0       ; if L1 is zero then H1 is good. 
        !            97:        beq     L_use_H1                ; else H2 will be good.
        !            98: 
        !            99:        mr      r6,     r8              ; use H2 instead.
        !           100: 
        !           101: L_use_H1:
        !           102:        rlwimi  r7,     r6,     8, 16, 23
        !           103:        not     r6,     r7              ; neg - 1 is not
        !           104:        andi.   r6,     r6,     0xffff
        !           105:        stw     r6,     4(r3)           ; save via ticks
        !           106: 
        !           107:        sub     r5,     r5,     r10     ; r5 is the number of time base ticks
        !           108:        stw     r5,     8(r3)           ; save time base ticks
        !           109: 
        !           110:         blr

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