From fc8c76f42e5231c215433fa5c5c4be951fd5eb56 Mon Sep 17 00:00:00 2001 From: Lukas Auer Date: Thu, 22 Nov 2018 11:26:18 +0100 Subject: 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 Reviewed-by: Bin Meng Reviewed-by: Rick Chen --- arch/riscv/include/asm/barrier.h | 67 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 67 insertions(+) create mode 100644 arch/riscv/include/asm/barrier.h (limited to 'arch/riscv/include/asm/barrier.h') diff --git a/arch/riscv/include/asm/barrier.h b/arch/riscv/include/asm/barrier.h new file mode 100644 index 0000000000..a3f60a8458 --- /dev/null +++ b/arch/riscv/include/asm/barrier.h @@ -0,0 +1,67 @@ +/* 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 */ -- cgit v1.2.3