text: /* SPDX-License-Identifier: GPL-2.0-only */
  /*
   * xchg/cmpxchg operations for the Hexagon architecture
   *
   * Copyright (c) 2010-2011, The Linux Foundation. All rights reserved.
   */
  
  #ifndef _ASM_CMPXCHG_H
  #define _ASM_CMPXCHG_H
  
  /*
   * __xchg - atomically exchange a register and a memory location
   * @x: value to swap
   * @ptr: pointer to memory
   * @size:  size of the value
   *
   * Only 4 bytes supported currently.
   *
   * Note:  there was an errata for V2 about .new's and memw_locked.
   *
   */
  static inline unsigned long __xchg(unsigned long x, volatile void *ptr,
  				   int size)
  {
  	unsigned long retval;
  
  	/*  Can't seem to use printk or panic here, so just stop  */
  	if (size != 4) do { asm volatile("brkpt;\n"); } while (1);
  
  	__asm__ __volatile__ (
  	"1:	%0 = memw_locked(%1);\n"    /*  load into retval */
  	"	memw_locked(%1,P0) = %2;\n" /*  store into memory */
  	"	if (!P0) jump 1b;\n"
  	: "=&r" (retval)
  	: "r" (ptr), "r" (x)
  	: "memory", "p0"
  	);
  	return retval;
  }
  
  /*
   * Atomically swap the contents of a register with memory.  Should be atomic
   * between multiple CPU's and within interrupts on the same CPU.
   */
  #define arch_xchg(ptr, v) ((__typeof__(*(ptr)))__xchg((unsigned long)(v), (ptr), \
  	sizeof(*(ptr))))
  
  /*
   *  see rt-mutex-design.txt; cmpxchg supposedly checks if *ptr == A and swaps.
   *  looks just like atomic_cmpxchg on our arch currently with a bunch of
   *  variable casting.
   */
  
  #define arch_cmpxchg(ptr, old, new)				\
  ({								\
  	__typeof__(ptr) __ptr = (ptr);				\
  	__typeof__(*(ptr)) __old = (old);			\
  	__typeof__(*(ptr)) __new = (new);			\
  	__typeof__(*(ptr)) __oldval = 0;			\
  								\
  	asm volatile(						\
  		"1:	%0 = memw_locked(%1);\n"		\
  		"	{ P0 = cmp.eq(%0,%2);\n"		\
  		"	  if (!P0.new) jump:nt 2f; }\n"		\
  		"	memw_locked(%1,p0) = %3;\n"		\
  		"	if (!P0) jump 1b;\n"			\
  		"2:\n"						\
  		: "=&r" (__oldval)				\
  		: "r" (__ptr), "r" (__old), "r" (__new)		\
  		: "memory", "p0"				\
  	);							\
  	__oldval;						\
  })
  
  #endif /* _ASM_CMPXCHG_H */
  