1/*
2 * xchg/cmpxchg operations for the Hexagon architecture
3 *
4 * Copyright (c) 2010-2011, The Linux Foundation. All rights reserved.
5 *
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 and
9 * only version 2 as published by the Free Software Foundation.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14 * GNU General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
19 * 02110-1301, USA.
20 */
21
22#ifndef _ASM_CMPXCHG_H
23#define _ASM_CMPXCHG_H
24
25/*
26 * __xchg - atomically exchange a register and a memory location
27 * @x: value to swap
28 * @ptr: pointer to memory
29 * @size:  size of the value
30 *
31 * Only 4 bytes supported currently.
32 *
33 * Note:  there was an errata for V2 about .new's and memw_locked.
34 *
35 */
36static inline unsigned long __xchg(unsigned long x, volatile void *ptr,
37				   int size)
38{
39	unsigned long retval;
40
41	/*  Can't seem to use printk or panic here, so just stop  */
42	if (size != 4) do { asm volatile("brkpt;\n"); } while (1);
43
44	__asm__ __volatile__ (
45	"1:	%0 = memw_locked(%1);\n"    /*  load into retval */
46	"	memw_locked(%1,P0) = %2;\n" /*  store into memory */
47	"	if !P0 jump 1b;\n"
48	: "=&r" (retval)
49	: "r" (ptr), "r" (x)
50	: "memory", "p0"
51	);
52	return retval;
53}
54
55/*
56 * Atomically swap the contents of a register with memory.  Should be atomic
57 * between multiple CPU's and within interrupts on the same CPU.
58 */
59#define xchg(ptr, v) ((__typeof__(*(ptr)))__xchg((unsigned long)(v), (ptr), \
60	sizeof(*(ptr))))
61
62/*
63 *  see rt-mutex-design.txt; cmpxchg supposedly checks if *ptr == A and swaps.
64 *  looks just like atomic_cmpxchg on our arch currently with a bunch of
65 *  variable casting.
66 */
67#define __HAVE_ARCH_CMPXCHG 1
68
69#define cmpxchg(ptr, old, new)					\
70({								\
71	__typeof__(ptr) __ptr = (ptr);				\
72	__typeof__(*(ptr)) __old = (old);			\
73	__typeof__(*(ptr)) __new = (new);			\
74	__typeof__(*(ptr)) __oldval = 0;			\
75								\
76	asm volatile(						\
77		"1:	%0 = memw_locked(%1);\n"		\
78		"	{ P0 = cmp.eq(%0,%2);\n"		\
79		"	  if (!P0.new) jump:nt 2f; }\n"		\
80		"	memw_locked(%1,p0) = %3;\n"		\
81		"	if (!P0) jump 1b;\n"			\
82		"2:\n"						\
83		: "=&r" (__oldval)				\
84		: "r" (__ptr), "r" (__old), "r" (__new)		\
85		: "memory", "p0"				\
86	);							\
87	__oldval;						\
88})
89
90#endif /* _ASM_CMPXCHG_H */
91