mirror of https://gitee.com/openkylin/linux.git
36 lines
1.5 KiB
C
36 lines
1.5 KiB
C
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#ifndef __PARISC_BARRIER_H
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#define __PARISC_BARRIER_H
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/*
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** This is simply the barrier() macro from linux/kernel.h but when serial.c
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** uses tqueue.h uses smp_mb() defined using barrier(), linux/kernel.h
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** hasn't yet been included yet so it fails, thus repeating the macro here.
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**
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** PA-RISC architecture allows for weakly ordered memory accesses although
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** none of the processors use it. There is a strong ordered bit that is
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** set in the O-bit of the page directory entry. Operating systems that
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** can not tolerate out of order accesses should set this bit when mapping
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** pages. The O-bit of the PSW should also be set to 1 (I don't believe any
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** of the processor implemented the PSW O-bit). The PCX-W ERS states that
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** the TLB O-bit is not implemented so the page directory does not need to
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** have the O-bit set when mapping pages (section 3.1). This section also
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** states that the PSW Y, Z, G, and O bits are not implemented.
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** So it looks like nothing needs to be done for parisc-linux (yet).
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** (thanks to chada for the above comment -ggg)
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**
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** The __asm__ op below simple prevents gcc/ld from reordering
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** instructions across the mb() "call".
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*/
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#define mb() __asm__ __volatile__("":::"memory") /* barrier() */
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#define rmb() mb()
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#define wmb() mb()
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#define smp_mb() mb()
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#define smp_rmb() mb()
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#define smp_wmb() mb()
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#define smp_read_barrier_depends() do { } while(0)
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#define read_barrier_depends() do { } while(0)
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#define set_mb(var, value) do { var = value; mb(); } while (0)
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#endif /* __PARISC_BARRIER_H */
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