90a3ccb0be
sh variant of smp_store_mb() calls xchg() on !SMP which is stronger than implied by both the name and the documentation. define __smp_store_mb instead: code in asm-generic/barrier.h will then define smp_store_mb correctly depending on CONFIG_SMP. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Acked-by: Arnd Bergmann <arnd@arndb.de> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
41 lines
1.3 KiB
C
41 lines
1.3 KiB
C
/*
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* Copyright (C) 1999, 2000 Niibe Yutaka & Kaz Kojima
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* Copyright (C) 2002 Paul Mundt
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*/
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#ifndef __ASM_SH_BARRIER_H
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#define __ASM_SH_BARRIER_H
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#if defined(CONFIG_CPU_SH4A) || defined(CONFIG_CPU_SH5)
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#include <asm/cache_insns.h>
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#endif
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/*
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* A brief note on ctrl_barrier(), the control register write barrier.
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*
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* Legacy SH cores typically require a sequence of 8 nops after
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* modification of a control register in order for the changes to take
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* effect. On newer cores (like the sh4a and sh5) this is accomplished
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* with icbi.
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*
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* Also note that on sh4a in the icbi case we can forego a synco for the
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* write barrier, as it's not necessary for control registers.
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*
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* Historically we have only done this type of barrier for the MMUCR, but
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* it's also necessary for the CCR, so we make it generic here instead.
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*/
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#if defined(CONFIG_CPU_SH4A) || defined(CONFIG_CPU_SH5)
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#define mb() __asm__ __volatile__ ("synco": : :"memory")
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#define rmb() mb()
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#define wmb() mb()
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#define ctrl_barrier() __icbi(PAGE_OFFSET)
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#else
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#define ctrl_barrier() __asm__ __volatile__ ("nop;nop;nop;nop;nop;nop;nop;nop")
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#endif
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#define __smp_store_mb(var, value) do { (void)xchg(&var, value); } while (0)
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#define smp_store_mb(var, value) __smp_store_mb(var, value)
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#include <asm-generic/barrier.h>
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#endif /* __ASM_SH_BARRIER_H */
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