linux/arch/tile/include/asm/barrier.h

/*
 * Copyright 2010 Tilera Corporation. 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
 *   as published by the Free Software Foundation, version 2.
 *
 *   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, GOOD TITLE or
 *   NON INFRINGEMENT.  See the GNU General Public License for
 *   more details.
 */

#ifndef _ASM_TILE_BARRIER_H
#define _ASM_TILE_BARRIER_H

#ifndef __ASSEMBLY__

#include <linux/types.h>
#include <arch/chip.h>
#include <arch/spr_def.h>
#include <asm/timex.h>

#define __sync()	__insn_mf()

#include <hv/syscall_public.h>
/*
 * Issue an uncacheable load to each memory controller, then
 * wait until those loads have completed.
 */
static inline void __mb_incoherent(void)
{
	long clobber_r10;
	asm volatile("swint2"
		     : "=R10" (clobber_r10)
		     : "R10" (HV_SYS_fence_incoherent)
		     : "r0", "r1", "r2", "r3", "r4",
		       "r5", "r6", "r7", "r8", "r9",
		       "r11", "r12", "r13", "r14",
		       "r15", "r16", "r17", "r18", "r19",
		       "r20", "r21", "r22", "r23", "r24",
		       "r25", "r26", "r27", "r28", "r29");
}

/* Fence to guarantee visibility of stores to incoherent memory. */
static inline void
mb_incoherent(void)
{
	__insn_mf();

	{
#if CHIP_HAS_TILE_WRITE_PENDING()
		const unsigned long WRITE_TIMEOUT_CYCLES = 400;
		unsigned long start = get_cycles_low();
		do {
			if (__insn_mfspr(SPR_TILE_WRITE_PENDING) == 0)
				return;
		} while ((get_cycles_low() - start) < WRITE_TIMEOUT_CYCLES);
#endif /* CHIP_HAS_TILE_WRITE_PENDING() */
		(void) __mb_incoherent();
	}
}

#define fast_wmb()	__sync()
#define fast_rmb()	__sync()
#define fast_mb()	__sync()
#define fast_iob()	mb_incoherent()

#define wmb()		fast_wmb()
#define rmb()		fast_rmb()
#define mb()		fast_mb()
#define iob()		fast_iob()

#ifndef __tilegx__ /* 32 bit */
/*
 * We need to barrier before modifying the word, since the _atomic_xxx()
 * routines just tns the lock and then read/modify/write of the word.
 * But after the word is updated, the routine issues an "mf" before returning,
 * and since it's a function call, we don't even need a compiler barrier.
 */
#define __smp_mb__before_atomic()	__smp_mb()
#define __smp_mb__after_atomic()	do { } while (0)
#define smp_mb__after_atomic()	__smp_mb__after_atomic()
#else /* 64 bit */
#define __smp_mb__before_atomic()	__smp_mb()
#define __smp_mb__after_atomic()	__smp_mb()
#endif

/*
 * The TILE architecture does not do speculative reads; this ensures
 * that a control dependency also orders against loads and already provides
 * a LOAD->{LOAD,STORE} order and can forgo the additional RMB.
 */
#define smp_acquire__after_ctrl_dep()	barrier()

#include <asm-generic/barrier.h>

#endif /* !__ASSEMBLY__ */
#endif /* _ASM_TILE_BARRIER_H */