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d1be6a28b1
In preparation for removing all explicit mmiowb() calls from driver code, implement a tracking system in asm-generic based loosely on the PowerPC implementation. This allows architectures with a non-empty mmiowb() definition to have the barrier automatically inserted in spin_unlock() following a critical section containing an I/O write. Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Will Deacon <will.deacon@arm.com>
64 lines
1.7 KiB
C
64 lines
1.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __ASM_GENERIC_MMIOWB_H
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#define __ASM_GENERIC_MMIOWB_H
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/*
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* Generic implementation of mmiowb() tracking for spinlocks.
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*
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* If your architecture doesn't ensure that writes to an I/O peripheral
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* within two spinlocked sections on two different CPUs are seen by the
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* peripheral in the order corresponding to the lock handover, then you
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* need to follow these FIVE easy steps:
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*
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* 1. Implement mmiowb() (and arch_mmiowb_state() if you're fancy)
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* in asm/mmiowb.h, then #include this file
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* 2. Ensure your I/O write accessors call mmiowb_set_pending()
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* 3. Select ARCH_HAS_MMIOWB
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* 4. Untangle the resulting mess of header files
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* 5. Complain to your architects
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*/
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#ifdef CONFIG_MMIOWB
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#include <linux/compiler.h>
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#include <asm-generic/mmiowb_types.h>
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#ifndef arch_mmiowb_state
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#include <asm/percpu.h>
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#include <asm/smp.h>
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DECLARE_PER_CPU(struct mmiowb_state, __mmiowb_state);
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#define __mmiowb_state() this_cpu_ptr(&__mmiowb_state)
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#else
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#define __mmiowb_state() arch_mmiowb_state()
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#endif /* arch_mmiowb_state */
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static inline void mmiowb_set_pending(void)
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{
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struct mmiowb_state *ms = __mmiowb_state();
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ms->mmiowb_pending = ms->nesting_count;
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}
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static inline void mmiowb_spin_lock(void)
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{
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struct mmiowb_state *ms = __mmiowb_state();
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ms->nesting_count++;
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}
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static inline void mmiowb_spin_unlock(void)
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{
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struct mmiowb_state *ms = __mmiowb_state();
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if (unlikely(ms->mmiowb_pending)) {
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ms->mmiowb_pending = 0;
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mmiowb();
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}
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ms->nesting_count--;
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}
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#else
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#define mmiowb_set_pending() do { } while (0)
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#define mmiowb_spin_lock() do { } while (0)
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#define mmiowb_spin_unlock() do { } while (0)
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#endif /* CONFIG_MMIOWB */
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#endif /* __ASM_GENERIC_MMIOWB_H */
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