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SubjectRe: 2.5.69 Interrupt Latency
Date
Paul Fulghum wrote:

> One machine (server) was using usb-uhci and
> the other (laptop) was using usb-ohci.
>
> So it looks like something with USB in 2.5.68-bk11

The change below was part of 2.5.68-bk11, and adds a 20ms
delay to the uhci interrupt handler. Could that be
the culprit?

Arnd <><

ChangeSet 1.1042.1.129 2003/04/29 15:30:31 stern@rowland.harvard.edu
[PATCH] USB: Minor patch for uhci-hcd.c
--- 1.32/drivers/usb/host/uhci-hcd.c Mon Apr 14 11:51:40 2003
+++ 1.33/drivers/usb/host/uhci-hcd.c Fri Apr 18 13:37:24 2003
@@ -1283,7 +1283,8 @@
}

if (last_urb) {
- *end = (last_urb->start_frame + last_urb->number_of_packets) & 1023;
+ *end = (last_urb->start_frame + last_urb->number_of_packets *
+ last_urb->interval) & (UHCI_NUMFRAMES-1);
ret = 0;
} else
ret = -1; /* no previous urb found */
@@ -1933,9 +1934,10 @@

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

- outw(USBCMD_EGSM, io_addr + USBCMD);
-
uhci->is_suspended = 1;
+ smp_wmb();
+
+ outw(USBCMD_EGSM, io_addr + USBCMD);
}

static void wakeup_hc(struct uhci_hcd *uhci)
@@ -1945,6 +1947,9 @@

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

+ /* Global resume for 20ms */
+ outw(USBCMD_FGR | USBCMD_EGSM, io_addr + USBCMD);
+ wait_ms(20);
outw(0, io_addr + USBCMD);

/* wait for EOP to be sent */
@@ -1965,7 +1970,7 @@
int i;

for (i = 0; i < uhci->rh_numports; i++)
- connection |= (inw(io_addr + USBPORTSC1 + i * 2) & 0x1);
+ connection |= (inw(io_addr + USBPORTSC1 + i * 2) & USBPORTSC_CCS);

return connection;
}
-
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