u-boot/arch/riscv/include/asm/barrier.h
Lukas Auer fc8c76f42e riscv: make use of the barrier functions from Linux
Replace the barrier functions in arch/riscv/include/asm/io.h with those
defined in barrier.h, which is imported from Linux. This version is
modified to remove the include statement of asm-generic/barrier.h, which
is not available in U-Boot or required.

Signed-off-by: Lukas Auer <lukas.auer@aisec.fraunhofer.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Rick Chen <rick@andestech.com>
2018-11-26 13:57:30 +08:00

67 lines
1.9 KiB
C

/* SPDX-License-Identifier: GPL-2.0 */
/*
* Copyright (C) 2012 ARM Ltd.
* Copyright (C) 2013 Regents of the University of California
* Copyright (C) 2017 SiFive
*
* Taken from Linux arch/riscv/include/asm/barrier.h, which is based on
* arch/arm/include/asm/barrier.h
*/
#ifndef _ASM_RISCV_BARRIER_H
#define _ASM_RISCV_BARRIER_H
#ifndef __ASSEMBLY__
#define nop() __asm__ __volatile__ ("nop")
#define RISCV_FENCE(p, s) \
__asm__ __volatile__ ("fence " #p "," #s : : : "memory")
/* These barriers need to enforce ordering on both devices or memory. */
#define mb() RISCV_FENCE(iorw,iorw)
#define rmb() RISCV_FENCE(ir,ir)
#define wmb() RISCV_FENCE(ow,ow)
/* These barriers do not need to enforce ordering on devices, just memory. */
#define __smp_mb() RISCV_FENCE(rw,rw)
#define __smp_rmb() RISCV_FENCE(r,r)
#define __smp_wmb() RISCV_FENCE(w,w)
#define __smp_store_release(p, v) \
do { \
compiletime_assert_atomic_type(*p); \
RISCV_FENCE(rw,w); \
WRITE_ONCE(*p, v); \
} while (0)
#define __smp_load_acquire(p) \
({ \
typeof(*p) ___p1 = READ_ONCE(*p); \
compiletime_assert_atomic_type(*p); \
RISCV_FENCE(r,rw); \
___p1; \
})
/*
* This is a very specific barrier: it's currently only used in two places in
* the kernel, both in the scheduler. See include/linux/spinlock.h for the two
* orderings it guarantees, but the "critical section is RCsc" guarantee
* mandates a barrier on RISC-V. The sequence looks like:
*
* lr.aq lock
* sc lock <= LOCKED
* smp_mb__after_spinlock()
* // critical section
* lr lock
* sc.rl lock <= UNLOCKED
*
* The AQ/RL pair provides a RCpc critical section, but there's not really any
* way we can take advantage of that here because the ordering is only enforced
* on that one lock. Thus, we're just doing a full fence.
*/
#define smp_mb__after_spinlock() RISCV_FENCE(rw,rw)
#endif /* __ASSEMBLY__ */
#endif /* _ASM_RISCV_BARRIER_H */