/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * 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
 */
#include "ppc_asm.h"

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

        .text

/* udelay 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:
        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
        bcl     20,31,0f
0:      mflr    r6
        mtlr    r5
        addis   r5,r6,(timebase_period_ns-0b)@ha
        lwz     r5,(timebase_period_ns-0b)@l(r5)
        add     r4,r4,r5
        addi    r4,r4,-1
        divw    r4,r4,r5        /* BUS ticks */
1:      MFTBU(r5)
        MFTBL(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
        MFTBL(r6)
        cmpw    0,r6,r9
        blt     2b
3:      blr