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    SubjectRe: [patch 2/3] s3cmci - call pio_tasklet from IRQ
    Ben Dooks wrote:
    > On Mon, Sep 08, 2008 at 02:48:50PM +0200, Christer Weinigel wrote:
    >> Scheduling a tasklet to perform the pio transfer introduces a bit of
    >> extra processing, just call pio_tasklet directly from the interrupt
    >> instead. Writing up to 64 bytes to a FIFO is probably uses less CPU
    >> than scheduling a tasklet anyway.
    >
    > Hmm, i'd be interested to find out how long these are taking... I might
    > try and rig up something to test the time being taken via an SMDK.
    >
    > If the fifo read/writes are taking significant amounts of time, then the
    > pio tasklet will at least improve the interrupt latencies invloved, as
    > iirc we're currently running the main irq handler in IRQ_DISABLED mode
    > to stop any problems with re-enternancy.... I'll check this and see what
    > is going on.

    It should be possible to set a flag and then call the pio_task after the
    spin_unlock_irqrestore instead. I didn't want to do that to change as
    little of the logic as possible, but it's probably better to do that.

    I'm also thinking of changing send_request to do a busy wait for
    commands without data, that will probably need a bit larger changes.

    /Christer


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