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/*
* xchg/cmpxchg operations for the Hexagon architecture
*
* Copyright (c) 2010-2011, The Linux Foundation. All rights reserved.
*
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 and
* only version 2 as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA.
*/
#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 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 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 */
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