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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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