Messages in this thread | | | Subject | Re: 2.5.69 Interrupt Latency | From | Paul Fulghum <> | Date | 12 May 2003 09:06:09 -0500 |
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On Mon, 2003-05-12 at 08:57, Paul Fulghum wrote: > On Fri, 2003-05-09 at 16:28, Andrew Morton wrote: > > > This code was added to wakeup_hc(). It is called from uhci_irq(): > > > > + /* Global resume for 20ms */ > > + outw(USBCMD_FGR | USBCMD_EGSM, io_addr + USBCMD); > > + wait_ms(20); > > > > The changelog just says "Minor patch for uhci-hcd.c" > > > > Can you delete the wait_ms() and see if that is our culprit? > > This is the culprit. > > Removing this line corrects the latency problems on > the server. A 20ms delay seems pretty excessive for an > interrupt handler. I'm not sure what it is supposed to > accomplish, but this seems like something that should > be scheduled to run outside of the ISR. > > I must have messed up a test on the laptop that is > also showing latency problems. On the laptop the > problem *is* in both 2.5.68/2.5.69 and *is not* > eliminated by turning off USB. The laptop uses the > ohci driver anyways which is not effected by this patch. > The laptop does not show latency problems on 2.4.20. > > So the patch above is definately a problem, > but the problem I am seeing on the laptop > is something unrelated, but part of 2.5.x > (which I will investigate further). > > Thanks, > Paul
I forgot to add this snippet from the /var/log/messages file of the server in case it helps the USB maintainer in evaluating what to do about the above patch.
kernel: drivers/usb/host/uhci-hcd.c: USB Universal Host Controller Interface driver v2.0 kernel: uhci-hcd 00:04.2: Intel Corp. 82371AB/EB/MB PIIX4 kernel: uhci-hcd 00:04.2: irq 19, io base 0000fce0 kernel: Please use the 'usbfs' filetype instead, the 'usbdevfs' name is deprecated. kernel: uhci-hcd 00:04.2: new USB bus registered, assigned bus number 1 kernel: hub 1-0:0: USB hub found kernel: hub 1-0:0: 2 ports detected
-- Paul Fulghum, paulkf@microgate.com Microgate Corporation, http://www.microgate.com
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