| David Brazdil | 0f672f6 | 2019-12-10 10:32:29 +0000 | [diff] [blame] | 1 | /* SPDX-License-Identifier: GPL-2.0-or-later */ |
| Andrew Scull | b4b6d4a | 2019-01-02 15:54:55 +0000 | [diff] [blame] | 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 |
| Andrew Scull | b4b6d4a | 2019-01-02 15:54:55 +0000 | [diff] [blame] | 14 | */ |
| 15 | #include "ppc_asm.h" |
| 16 | |
| 17 | #define SPRN_PVR 0x11F /* Processor Version Register */ |
| 18 | |
| 19 | .text |
| 20 | |
| Olivier Deprez | 157378f | 2022-04-04 15:47:50 +0200 | [diff] [blame^] | 21 | /* udelay needs to know the period of the |
| Andrew Scull | b4b6d4a | 2019-01-02 15:54:55 +0000 | [diff] [blame] | 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: |
| Andrew Scull | b4b6d4a | 2019-01-02 15:54:55 +0000 | [diff] [blame] | 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 |