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); |
30 | #define __mmiowb_state() raw_cpu_ptr(&__mmiowb_state) |
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(); |
38 | |
39 | if (likely(ms->nesting_count)) |
40 | ms->mmiowb_pending = ms->nesting_count; |
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 */ |
66 | |