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    SubjectRe: [PATCH][RFC] asm-generic:remove calling flush_write_buffers() in dma_sync_*_for_cpu
    On Mon, Jun 29, 2009 at 10:54:51PM +0800, Ming Lei wrote:
    > 2009/6/29 Joerg Roedel <>:
    > >>
    > >> IMHO, even we do not call flush_write_buffer(), CPU can read correct
    > >> data from the
    > >> dma buffer since write buffer can't affect cache, right?
    > >
    > > flush_write_buffer is not about cache flushing. It is about read/write
    > > reordering in the CPU. Think of it as a memory barrier. On most x86
    > You mean we may need a memory barrier between writing data from bouncing buffer
    > to dma buffer and reading data from dma buffer, do you?

    CONFIG_X86_OOSTORE (when set flush_write_buffers is a memory barrier and not a
    nop on x86) is defined for WINCHIP. So it seems necessary on some chips.


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