[lkml]   [2009]   [Jun]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    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.


    | Advanced Micro Devices GmbH
    Operating | Karl-Hammerschmidt-Str. 34, 85609 Dornach bei München
    System |
    Research | Geschäftsführer: Thomas M. McCoy, Giuliano Meroni
    Center | Sitz: Dornach, Gemeinde Aschheim, Landkreis München
    | Registergericht München, HRB Nr. 43632

    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2009-06-29 17:47    [W:0.024 / U:8.884 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site