Re: 2.5.69 Interrupt Latency

Greg KH (greg@kroah.com)
Tue, 13 May 2003 10:30:44 -0700


On Tue, May 13, 2003 at 10:35:07AM -0500, Paul Fulghum wrote:
> On Tue, 2003-05-13 at 10:26, Alan Stern wrote:
>
> > Putting in a sanity check for the global suspend state will be very easy.
> > But I would like to point out that this "global suspend" does not refer to
> > the entire system, only the USB bus.
>
> That is a problem then, because the delay can still
> occur during normal system operation.

Ok, can you try the attached patch and see if it causes your latency
problem to go away?

thanks,

greg k-h

--- a/drivers/usb/host/uhci-hcd.c Sun May 4 23:49:54 2003
+++ b/drivers/usb/host/uhci-hcd.c Tue May 13 10:26:02 2003
@@ -1947,6 +1947,11 @@

dbg("%x: wakeup_hc", io_addr);

+ /* Verify that we really should wake up the hc */
+ status = inw(io_addr + USBCMD);
+ if (!(status & USBCMD_EGSM))
+ return;
+
/* Global resume for 20ms */
outw(USBCMD_FGR | USBCMD_EGSM, io_addr + USBCMD);
wait_ms(20);
-
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