Subversion Repositories or1k_soc_on_altera_embedded_dev_kit

/*

 * Copied from 

 *

 * 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  

 * 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