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d1be6a28 WD |
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 | ||
29 | DECLARE_PER_CPU(struct mmiowb_state, __mmiowb_state); | |
bd024e82 | 30 | #define __mmiowb_state() raw_cpu_ptr(&__mmiowb_state) |
d1be6a28 WD |
31 | #else |
32 | #define __mmiowb_state() arch_mmiowb_state() | |
33 | #endif /* arch_mmiowb_state */ | |
34 | ||
35 | static inline void mmiowb_set_pending(void) | |
36 | { | |
37 | struct mmiowb_state *ms = __mmiowb_state(); | |
bd024e82 WD |
38 | |
39 | if (likely(ms->nesting_count)) | |
40 | ms->mmiowb_pending = ms->nesting_count; | |
d1be6a28 WD |
41 | } |
42 | ||
43 | static inline void mmiowb_spin_lock(void) | |
44 | { | |
45 | struct mmiowb_state *ms = __mmiowb_state(); | |
46 | ms->nesting_count++; | |
47 | } | |
48 | ||
49 | static 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 */ |