USB: EHCI: use hrtimer for interrupt QH unlink
This patch (as1577) adds hrtimer support for unlinking interrupt QHs
in ehci-hcd. The current code relies on a fixed delay of either 2 or
55 us, which is not always adequate and in any case is totally bogus.
Thanks to internal caching, the EHCI hardware may continue to access
an interrupt QH for more than a millisecond after it has been unlinked.
In fact, the EHCI spec doesn't say how long to wait before using an
unlinked interrupt QH. The patch sets the delay to 9 microframes
minimum, which ought to be adequate.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/usb/host/ehci-timer.c b/drivers/usb/host/ehci-timer.c
index 1e907dd..bd8b591 100644
--- a/drivers/usb/host/ehci-timer.c
+++ b/drivers/usb/host/ehci-timer.c
@@ -69,6 +69,7 @@
static unsigned event_delays_ns[] = {
1 * NSEC_PER_MSEC, /* EHCI_HRTIMER_POLL_ASS */
1 * NSEC_PER_MSEC, /* EHCI_HRTIMER_POLL_PSS */
+ 1125 * NSEC_PER_USEC, /* EHCI_HRTIMER_UNLINK_INTR */
10 * NSEC_PER_MSEC, /* EHCI_HRTIMER_DISABLE_PERIODIC */
15 * NSEC_PER_MSEC, /* EHCI_HRTIMER_DISABLE_ASYNC */
};
@@ -192,6 +193,38 @@
}
+/* Handle unlinked interrupt QHs once they are gone from the hardware */
+static void ehci_handle_intr_unlinks(struct ehci_hcd *ehci)
+{
+ bool stopped = (ehci->rh_state < EHCI_RH_RUNNING);
+
+ /*
+ * Process all the QHs on the intr_unlink list that were added
+ * before the current unlink cycle began. The list is in
+ * temporal order, so stop when we reach the first entry in the
+ * current cycle. But if the root hub isn't running then
+ * process all the QHs on the list.
+ */
+ ehci->intr_unlinking = true;
+ while (ehci->intr_unlink) {
+ struct ehci_qh *qh = ehci->intr_unlink;
+
+ if (!stopped && qh->unlink_cycle == ehci->intr_unlink_cycle)
+ break;
+ ehci->intr_unlink = qh->unlink_next;
+ qh->unlink_next = NULL;
+ end_unlink_intr(ehci, qh);
+ }
+
+ /* Handle remaining entries later */
+ if (ehci->intr_unlink) {
+ ehci_enable_event(ehci, EHCI_HRTIMER_UNLINK_INTR, true);
+ ++ehci->intr_unlink_cycle;
+ }
+ ehci->intr_unlinking = false;
+}
+
+
/*
* Handler functions for the hrtimer event types.
* Keep this array in the same order as the event types indexed by
@@ -200,6 +233,7 @@
static void (*event_handlers[])(struct ehci_hcd *) = {
ehci_poll_ASS, /* EHCI_HRTIMER_POLL_ASS */
ehci_poll_PSS, /* EHCI_HRTIMER_POLL_PSS */
+ ehci_handle_intr_unlinks, /* EHCI_HRTIMER_UNLINK_INTR */
ehci_disable_PSE, /* EHCI_HRTIMER_DISABLE_PERIODIC */
ehci_disable_ASE, /* EHCI_HRTIMER_DISABLE_ASYNC */
};