forked from Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
104 lines
2.7 KiB
104 lines
2.7 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
|
/* |
|
* Copyright (C) 2017 Imagination Technologies |
|
* Author: Paul Burton <[email protected]> |
|
*/ |
|
|
|
#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 = arch_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 = arch_cmpxchg(ptr32, old32, new32); |
|
if (load32 == old32) |
|
return old; |
|
} |
|
}
|
|
|