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 */