1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef __ASM_GENERIC_MMIOWB_H
3#define __ASM_GENERIC_MMIOWB_H
4
5/*
6 * Generic implementation of mmiowb() tracking for spinlocks.
7 *
8 * If your architecture doesn't ensure that writes to an I/O peripheral
9 * within two spinlocked sections on two different CPUs are seen by the
10 * peripheral in the order corresponding to the lock handover, then you
11 * need to follow these FIVE easy steps:
12 *
13 * 1. Implement mmiowb() (and arch_mmiowb_state() if you're fancy)
14 * in asm/mmiowb.h, then #include this file
15 * 2. Ensure your I/O write accessors call mmiowb_set_pending()
16 * 3. Select ARCH_HAS_MMIOWB
17 * 4. Untangle the resulting mess of header files
18 * 5. Complain to your architects
19 */
20#ifdef CONFIG_MMIOWB
21
22#include <linux/compiler.h>
23#include <asm-generic/mmiowb_types.h>
24
25#ifndef arch_mmiowb_state
26#include <asm/percpu.h>
27#include <asm/smp.h>
28
29DECLARE_PER_CPU(struct mmiowb_state, __mmiowb_state);
30#define __mmiowb_state() raw_cpu_ptr(&__mmiowb_state)
31#else
32#define __mmiowb_state() arch_mmiowb_state()
33#endif /* arch_mmiowb_state */
34
35static inline void mmiowb_set_pending(void)
36{
37 struct mmiowb_state *ms = __mmiowb_state();
38
39 if (likely(ms->nesting_count))
40 ms->mmiowb_pending = ms->nesting_count;
41}
42
43static inline void mmiowb_spin_lock(void)
44{
45 struct mmiowb_state *ms = __mmiowb_state();
46 ms->nesting_count++;
47}
48
49static inline void mmiowb_spin_unlock(void)
50{
51 struct mmiowb_state *ms = __mmiowb_state();
52
53 if (unlikely(ms->mmiowb_pending)) {
54 ms->mmiowb_pending = 0;
55 mmiowb();
56 }
57
58 ms->nesting_count--;
59}
60#else
61#define mmiowb_set_pending() do { } while (0)
62#define mmiowb_spin_lock() do { } while (0)
63#define mmiowb_spin_unlock() do { } while (0)
64#endif /* CONFIG_MMIOWB */
65#endif /* __ASM_GENERIC_MMIOWB_H */
66