On Fri, 29 Aug 2008, Alan Stern wrote:
> > Does this sound at all logical and feasible?
>
> The first proposal is feasible; I can write a patch to implement it.
> How much it will end up helping anything isn't clear, though.
Here's the promised patch. Be warned, I haven't tested it at all.
Alan Stern
Index: usb-2.6/drivers/usb/core/hcd.h
===================================================================
--- usb-2.6.orig/drivers/usb/core/hcd.h
+++ usb-2.6/drivers/usb/core/hcd.h
@@ -486,4 +486,7 @@ static inline void usbmon_urb_complete(s
*/
extern struct rw_semaphore ehci_cf_port_reset_rwsem;
+/* This is also for use by khubd and ehci-hcd. */
+extern void usb_wait_for_khubd_idle(void);
+
#endif /* __KERNEL__ */
Index: usb-2.6/drivers/usb/core/hub.c
===================================================================
--- usb-2.6.orig/drivers/usb/core/hub.c
+++ usb-2.6/drivers/usb/core/hub.c
@@ -3097,6 +3097,16 @@ loop:
} /* end while (1) */
}
+/* Let ehci-hcd know when khubd is idle */
+static int khubd_active;
+static DECLARE_WAIT_QUEUE_HEAD(khubd_wqh);
+
+void usb_wait_for_khubd_idle(void)
+{
+ wait_event(khubd_wqh, !khubd_active);
+}
+EXPORT_SYMBOL_GPL(usb_wait_for_khubd_idle);
+
static int hub_thread(void *__unused)
{
/* khubd needs to be freezable to avoid intefering with USB-PERSIST
@@ -3107,7 +3117,11 @@ static int hub_thread(void *__unused)
set_freezable();
do {
+ khubd_active = 1;
hub_events();
+ khubd_active = 0;
+ wake_up_all(&khubd_wqh);
+
wait_event_freezable(khubd_wait,
!list_empty(&hub_event_list) ||
kthread_should_stop());
Index: usb-2.6/drivers/usb/host/ehci-hcd.c
===================================================================
--- usb-2.6.orig/drivers/usb/host/ehci-hcd.c
+++ usb-2.6/drivers/usb/host/ehci-hcd.c
@@ -604,7 +604,13 @@ static int ehci_run (struct usb_hcd *hcd
* guarantees that no resets are in progress. After we set CF,
* a short delay lets the hardware catch up; new resets shouldn't
* be started before the port switching actions could complete.
+ *
+ * In an attempt to avoid unwanted initialization error messages
+ * for devices attached to companion controllers, we will wait
+ * until khubd is idle before beginning. This isn't truly a
+ * general solution but it should help during system bootup.
*/
+ usb_wait_for_khubd_idle();
down_write(&ehci_cf_port_reset_rwsem);
hcd->state = HC_STATE_RUNNING;
ehci_writel(ehci, FLAG_CF, &ehci->regs->configured_flag);
--
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