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- /* SPDX-License-Identifier: GPL-2.0 */
- #ifndef __ASM_GENERIC_MMIOWB_H
- #define __ASM_GENERIC_MMIOWB_H
- /*
- * Generic implementation of mmiowb() tracking for spinlocks.
- *
- * If your architecture doesn't ensure that writes to an I/O peripheral
- * within two spinlocked sections on two different CPUs are seen by the
- * peripheral in the order corresponding to the lock handover, then you
- * need to follow these FIVE easy steps:
- *
- * 1. Implement mmiowb() (and arch_mmiowb_state() if you're fancy)
- * in asm/mmiowb.h, then #include this file
- * 2. Ensure your I/O write accessors call mmiowb_set_pending()
- * 3. Select ARCH_HAS_MMIOWB
- * 4. Untangle the resulting mess of header files
- * 5. Complain to your architects
- */
- #ifdef CONFIG_MMIOWB
- #include <linux/compiler.h>
- #include <asm-generic/mmiowb_types.h>
- #ifndef arch_mmiowb_state
- #include <asm/percpu.h>
- #include <asm/smp.h>
- DECLARE_PER_CPU(struct mmiowb_state, __mmiowb_state);
- #define __mmiowb_state() raw_cpu_ptr(&__mmiowb_state)
- #else
- #define __mmiowb_state() arch_mmiowb_state()
- #endif /* arch_mmiowb_state */
- static inline void mmiowb_set_pending(void)
- {
- struct mmiowb_state *ms = __mmiowb_state();
- if (likely(ms->nesting_count))
- ms->mmiowb_pending = ms->nesting_count;
- }
- static inline void mmiowb_spin_lock(void)
- {
- struct mmiowb_state *ms = __mmiowb_state();
- ms->nesting_count++;
- }
- static inline void mmiowb_spin_unlock(void)
- {
- struct mmiowb_state *ms = __mmiowb_state();
- if (unlikely(ms->mmiowb_pending)) {
- ms->mmiowb_pending = 0;
- mmiowb();
- }
- ms->nesting_count--;
- }
- #else
- #define mmiowb_set_pending() do { } while (0)
- #define mmiowb_spin_lock() do { } while (0)
- #define mmiowb_spin_unlock() do { } while (0)
- #endif /* CONFIG_MMIOWB */
- #endif /* __ASM_GENERIC_MMIOWB_H */
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