linux/arch/mips/kernel/cmpxchg.c
Thomas Gleixner 2874c5fd28 treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152
Based on 1 normalized pattern(s):

  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

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 3029 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070032.746973796@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-05-30 11:26:32 -07:00

105 lines
2.7 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright (C) 2017 Imagination Technologies
* Author: Paul Burton <paul.burton@mips.com>
*/
#include <linux/bitops.h>
#include <asm/cmpxchg.h>
unsigned long __xchg_small(volatile void *ptr, unsigned long val, unsigned int size)
{
u32 old32, new32, load32, mask;
volatile u32 *ptr32;
unsigned int shift;
/* Check that ptr is naturally aligned */
WARN_ON((unsigned long)ptr & (size - 1));
/* Mask value to the correct size. */
mask = GENMASK((size * BITS_PER_BYTE) - 1, 0);
val &= mask;
/*
* Calculate a shift & mask that correspond to the value we wish to
* exchange within the naturally aligned 4 byte integerthat includes
* it.
*/
shift = (unsigned long)ptr & 0x3;
if (IS_ENABLED(CONFIG_CPU_BIG_ENDIAN))
shift ^= sizeof(u32) - size;
shift *= BITS_PER_BYTE;
mask <<= shift;
/*
* Calculate a pointer to the naturally aligned 4 byte integer that
* includes our byte of interest, and load its value.
*/
ptr32 = (volatile u32 *)((unsigned long)ptr & ~0x3);
load32 = *ptr32;
do {
old32 = load32;
new32 = (load32 & ~mask) | (val << shift);
load32 = cmpxchg(ptr32, old32, new32);
} while (load32 != old32);
return (load32 & mask) >> shift;
}
unsigned long __cmpxchg_small(volatile void *ptr, unsigned long old,
unsigned long new, unsigned int size)
{
u32 mask, old32, new32, load32, load;
volatile u32 *ptr32;
unsigned int shift;
/* Check that ptr is naturally aligned */
WARN_ON((unsigned long)ptr & (size - 1));
/* Mask inputs to the correct size. */
mask = GENMASK((size * BITS_PER_BYTE) - 1, 0);
old &= mask;
new &= mask;
/*
* Calculate a shift & mask that correspond to the value we wish to
* compare & exchange within the naturally aligned 4 byte integer
* that includes it.
*/
shift = (unsigned long)ptr & 0x3;
if (IS_ENABLED(CONFIG_CPU_BIG_ENDIAN))
shift ^= sizeof(u32) - size;
shift *= BITS_PER_BYTE;
mask <<= shift;
/*
* Calculate a pointer to the naturally aligned 4 byte integer that
* includes our byte of interest, and load its value.
*/
ptr32 = (volatile u32 *)((unsigned long)ptr & ~0x3);
load32 = *ptr32;
while (true) {
/*
* Ensure the byte we want to exchange matches the expected
* old value, and if not then bail.
*/
load = (load32 & mask) >> shift;
if (load != old)
return load;
/*
* Calculate the old & new values of the naturally aligned
* 4 byte integer that include the byte we want to exchange.
* Attempt to exchange the old value for the new value, and
* return if we succeed.
*/
old32 = (load32 & ~mask) | (old << shift);
new32 = (load32 & ~mask) | (new << shift);
load32 = cmpxchg(ptr32, old32, new32);
if (load32 == old32)
return old;
}
}