// 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 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; 	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;	}}EXPORT_SYMBOL(__cmpxchg_small);