1 /* SPDX-License-Identifier: GPL-2.0-or-later */ 2 /* 3 * Copied from <file:arch/powerpc/kernel/misc_32.S> 4 * 5 * This file contains miscellaneous low-level functions. 6 * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org) 7 * 8 * Largely rewritten by Cort Dougan (cort@cs.nmt.edu) 9 * and Paul Mackerras. 10 * 11 * kexec bits: 12 * Copyright (C) 2002-2003 Eric Biederman <ebiederm@xmission.com> 13 * GameCube/ppc32 port Copyright (C) 2004 Albert Herranz 14 */ 15 #include "ppc_asm.h" 16 17 #define SPRN_PVR 0x11F /* Processor Version Register */ 18 19 .text 20 21 /* udelay needs to know the period of the 22 * timebase in nanoseconds. This used to be hardcoded to be 60ns 23 * (period of 66MHz/4). Now a variable is used that is initialized to 24 * 60 for backward compatibility, but it can be overridden as necessary 25 * with code something like this: 26 * extern unsigned long timebase_period_ns; 27 * timebase_period_ns = 1000000000 / bd->bi_tbfreq; 28 */ 29 .data 30 .globl timebase_period_ns 31 timebase_period_ns: 32 .long 60 33 34 .text 35 /* 36 * Delay for a number of microseconds 37 */ 38 .globl udelay 39 udelay: 40 mulli r4,r3,1000 /* nanoseconds */ 41 /* Change r4 to be the number of ticks using: 42 * (nanoseconds + (timebase_period_ns - 1 )) / timebase_period_ns 43 * timebase_period_ns defaults to 60 (16.6MHz) */ 44 mflr r5 45 bl 0f 46 0: mflr r6 47 mtlr r5 48 lis r5,0b@ha 49 addi r5,r5,0b@l 50 subf r5,r5,r6 /* In case we're relocated */ 51 addis r5,r5,timebase_period_ns@ha 52 lwz r5,timebase_period_ns@l(r5) 53 add r4,r4,r5 54 addi r4,r4,-1 55 divw r4,r4,r5 /* BUS ticks */ 56 1: MFTBU(r5) 57 MFTBL(r6) 58 MFTBU(r7) 59 cmpw 0,r5,r7 60 bne 1b /* Get [synced] base time */ 61 addc r9,r6,r4 /* Compute end time */ 62 addze r8,r5 63 2: MFTBU(r5) 64 cmpw 0,r5,r8 65 blt 2b 66 bgt 3f 67 MFTBL(r6) 68 cmpw 0,r6,r9 69 blt 2b 70 3: blr 71