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    SubjectRe: [RFC] Relaxed PIO read vs. DMA write ordering
    On Wed, Jan 07, 2004 at 03:27:54PM -0800, Greg KH wrote:
    > On Wed, Jan 07, 2004 at 03:07:12PM -0800, Jesse Barnes wrote:
    > >
    > > 1) add pcix_enable_relaxed() and read_relaxed() (read() would always be
    > > ordered)
    > This probably preserves the current situation best, enabling driver
    > writers to be explicit in knowing what is happening.
    > thanks,
    > greg k-h

    I like this best too. That way, a driver can enable a relaxed read
    in the performance path and not have to audit the other reads.

    So in a generic PCI driver, you'd call pcix_enable_relaxed() and
    then use read() for initialization, error recovery, etc., and
    use read_relaxed() in the main execution path where it is determined
    to be safe.

    The default would be the standard behavior that we have.

    One question I have is what the need for pcix_enable_relaxed() is.
    Are we thinking that this sets some bit in one or more registers?
    What happens if you use read_relaxed() and you didn't call
    pcix_enable_relaxed() previously?

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