Subversion Repositories or1k_soc_on_altera_embedded_dev_kit

/*
 * Copied from <file:arch/powerpc/kernel/misc_32.S>
 *
 * This file contains miscellaneous low-level functions.
 *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
 *
 * Largely rewritten by Cort Dougan (cort@cs.nmt.edu)
 * and Paul Mackerras.
 *
 * kexec bits:
 * Copyright (C) 2002-2003 Eric Biederman  <ebiederm@xmission.com>
 * GameCube/ppc32 port Copyright (C) 2004 Albert Herranz
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 *
 */
#include "ppc_asm.h"

#define SPRN_PVR        0x11F   /* Processor Version Register */

        .text

/* udelay (on non-601 processors) needs to know the period of the
 * timebase in nanoseconds.  This used to be hardcoded to be 60ns
 * (period of 66MHz/4).  Now a variable is used that is initialized to
 * 60 for backward compatibility, but it can be overridden as necessary
 * with code something like this:
 *    extern unsigned long timebase_period_ns;
 *    timebase_period_ns = 1000000000 / bd->bi_tbfreq;
 */
        .data
        .globl timebase_period_ns
timebase_period_ns:
        .long   60

        .text
/*
 * Delay for a number of microseconds
 */
        .globl  udelay
udelay:
        mfspr   r4,SPRN_PVR
        srwi    r4,r4,16
        cmpwi   0,r4,1          /* 601 ? */
        bne     .udelay_not_601
00:     li      r0,86   /* Instructions / microsecond? */
        mtctr   r0
10:     addi    r0,r0,0 /* NOP */
        bdnz    10b
        subic.  r3,r3,1
        bne     00b
        blr

.udelay_not_601:
        mulli   r4,r3,1000      /* nanoseconds */
        /*  Change r4 to be the number of ticks using:
         *      (nanoseconds + (timebase_period_ns - 1 )) / timebase_period_ns
         *  timebase_period_ns defaults to 60 (16.6MHz) */
        mflr    r5
        bl      0f
0:      mflr    r6
        mtlr    r5
        lis     r5,0b@ha
        addi    r5,r5,0b@l
        subf    r5,r5,r6        /* In case we're relocated */
        addis   r5,r5,timebase_period_ns@ha
        lwz     r5,timebase_period_ns@l(r5)
        add     r4,r4,r5
        addi    r4,r4,-1
        divw    r4,r4,r5        /* BUS ticks */
1:      mftbu   r5
        mftb    r6
        mftbu   r7
        cmpw    0,r5,r7
        bne     1b              /* Get [synced] base time */
        addc    r9,r6,r4        /* Compute end time */
        addze   r8,r5
2:      mftbu   r5
        cmpw    0,r5,r8
        blt     2b
        bgt     3f
        mftb    r6
        cmpw    0,r6,r9
        blt     2b
3:      blr