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    SubjectRe: Test Patch: 2.5.69 Interrupt Latency
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    On Fri, 2003-05-16 at 10:33, Alan Stern wrote:
    > Paul:
    >
    > On 15 May 2003, Paul Fulghum wrote:
    > > Con: you would be generating a lot of spurious interrupts
    > > as the global USBSTS_RD is set (incorrectly) by the OC ports.
    > > Even though you would not actually do the wake, you still
    > > burn cycles servicing the false interrupts.
    >
    > I'm not sure about that. For ports in a permanent OC state, the RD bit
    > would get set just once, so a single interrupt would be generated. When
    > the host clears the Resume Detect bit in the USBSTS register, it shouldn't
    > get set again (not until a different port signals a resume). Otherwise a
    > properly working system would generate continuous interrupts during the
    > global resume sequence.

    Your interpretation checks out. The global RD interrupt does not
    reoccur once the individual RD bit is set. So we get a max of
    once extra interrupt per OC port.

    --
    Paul Fulghum
    paulkf@microgate.com

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