1 /* SPDX-License-Identifier: GPL-2.0-only */ 2 /* 3 * xchg/cmpxchg operations for the Hexagon architecture 4 * 5 * Copyright (c) 2010-2011, The Linux Foundation. All rights reserved. 6 */ 7 8 #ifndef _ASM_CMPXCHG_H 9 #define _ASM_CMPXCHG_H 10 11 /* 12 * __xchg - atomically exchange a register and a memory location 13 * @x: value to swap 14 * @ptr: pointer to memory 15 * @size: size of the value 16 * 17 * Only 4 bytes supported currently. 18 * 19 * Note: there was an errata for V2 about .new's and memw_locked. 20 * 21 */ 22 static inline unsigned long __xchg(unsigned long x, volatile void *ptr, 23 int size) 24 { 25 unsigned long retval; 26 27 /* Can't seem to use printk or panic here, so just stop */ 28 if (size != 4) do { asm volatile("brkpt;\n"); } while (1); 29 30 __asm__ __volatile__ ( 31 "1: %0 = memw_locked(%1);\n" /* load into retval */ 32 " memw_locked(%1,P0) = %2;\n" /* store into memory */ 33 " if (!P0) jump 1b;\n" 34 : "=&r" (retval) 35 : "r" (ptr), "r" (x) 36 : "memory", "p0" 37 ); 38 return retval; 39 } 40 41 /* 42 * Atomically swap the contents of a register with memory. Should be atomic 43 * between multiple CPU's and within interrupts on the same CPU. 44 */ 45 #define xchg(ptr, v) ((__typeof__(*(ptr)))__xchg((unsigned long)(v), (ptr), \ 46 sizeof(*(ptr)))) 47 48 /* 49 * see rt-mutex-design.txt; cmpxchg supposedly checks if *ptr == A and swaps. 50 * looks just like atomic_cmpxchg on our arch currently with a bunch of 51 * variable casting. 52 */ 53 54 #define cmpxchg(ptr, old, new) \ 55 ({ \ 56 __typeof__(ptr) __ptr = (ptr); \ 57 __typeof__(*(ptr)) __old = (old); \ 58 __typeof__(*(ptr)) __new = (new); \ 59 __typeof__(*(ptr)) __oldval = 0; \ 60 \ 61 asm volatile( \ 62 "1: %0 = memw_locked(%1);\n" \ 63 " { P0 = cmp.eq(%0,%2);\n" \ 64 " if (!P0.new) jump:nt 2f; }\n" \ 65 " memw_locked(%1,p0) = %3;\n" \ 66 " if (!P0) jump 1b;\n" \ 67 "2:\n" \ 68 : "=&r" (__oldval) \ 69 : "r" (__ptr), "r" (__old), "r" (__new) \ 70 : "memory", "p0" \ 71 ); \ 72 __oldval; \ 73 }) 74 75 #endif /* _ASM_CMPXCHG_H */ 76