This patch (as1658) cleans up the usage of qh_completions() in
ehci-hcd. Currently the function's return value indicates whether any
URBs were given back; the idea was that the caller can scan the QH
over again to handle any URBs that were dequeued by a completion
handler. This is not necessary; when qh_completions() is ready to
give back dequeued URBs, it does its own rescanning.
Therefore the new return value will be a flag indicating whether the
caller needs to unlink the QH. This is more convenient than forcing
the caller to check qh->needs_rescan, and it makes a lot more sense --
why should "needs_rescan" imply that an unlink is needed? The callers
are also changed to remove the unneeded rescans.
Lastly, the check for whether qh->qtd_list is non-empty is removed
from the start of qh_completions(). Two of the callers have to make
this test anyway, so the same test can simply be added to the other
two callers.
Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
---
drivers/usb/host/ehci-q.c | 22 ++++++++--------------
drivers/usb/host/ehci-sched.c | 12 +++++-------
2 files changed, 13 insertions(+), 21 deletions(-)
Index: usb-3.9/drivers/usb/host/ehci-q.c
===================================================================
--- usb-3.9.orig/drivers/usb/host/ehci-q.c
+++ usb-3.9/drivers/usb/host/ehci-q.c
@@ -292,8 +292,8 @@ static int qh_schedule (struct ehci_hcd
/*
* Process and free completed qtds for a qh, returning URBs to drivers.
- * Chases up to qh->hw_current. Returns number of completions called,
- * indicating how much "real" work we did.
+ * Chases up to qh->hw_current. Returns nonzero if the caller should
+ * unlink qh.
*/
static unsigned
qh_completions (struct ehci_hcd *ehci, struct ehci_qh *qh)
@@ -302,13 +302,9 @@ qh_completions (struct ehci_hcd *ehci, s
struct list_head *entry, *tmp;
int last_status;
int stopped;
- unsigned count = 0;
u8 state;
struct ehci_qh_hw *hw = qh->hw;
- if (unlikely (list_empty (&qh->qtd_list)))
- return count;
-
/* completions (or tasks on other cpus) must never clobber HALT
* till we've gone through and cleaned everything up, even when
* they add urbs to this qh's queue or mark them for unlinking.
@@ -345,7 +341,6 @@ qh_completions (struct ehci_hcd *ehci, s
if (last) {
if (likely (last->urb != urb)) {
ehci_urb_done(ehci, last->urb, last_status);
- count++;
last_status = -EINPROGRESS;
}
ehci_qtd_free (ehci, last);
@@ -519,7 +514,6 @@ qh_completions (struct ehci_hcd *ehci, s
/* last urb's completion might still need calling */
if (likely (last != NULL)) {
ehci_urb_done(ehci, last->urb, last_status);
- count++;
ehci_qtd_free (ehci, last);
}
@@ -566,7 +560,7 @@ qh_completions (struct ehci_hcd *ehci, s
/* otherwise, unlink already started */
}
- return count;
+ return qh->needs_rescan;
}
/*-------------------------------------------------------------------------*/
@@ -1254,7 +1248,8 @@ static void end_unlink_async(struct ehci
qh->qh_state = QH_STATE_IDLE;
qh->qh_next.qh = NULL;
- qh_completions(ehci, qh);
+ if (!list_empty(&qh->qtd_list))
+ qh_completions(ehci, qh);
if (!list_empty(&qh->qtd_list) &&
ehci->rh_state == EHCI_RH_RUNNING)
qh_link_async(ehci, qh);
@@ -1348,7 +1343,7 @@ static void scan_async (struct ehci_hcd
while (ehci->qh_scan_next) {
qh = ehci->qh_scan_next;
ehci->qh_scan_next = qh->qh_next.qh;
- rescan:
+
/* clean any finished work for this qh */
if (!list_empty(&qh->qtd_list)) {
int temp;
@@ -1361,14 +1356,13 @@ static void scan_async (struct ehci_hcd
* in single_unlink_async().
*/
temp = qh_completions(ehci, qh);
- if (qh->needs_rescan) {
+ if (unlikely(temp)) {
start_unlink_async(ehci, qh);
} else if (list_empty(&qh->qtd_list)
&& qh->qh_state == QH_STATE_LINKED) {
qh->unlink_cycle = ehci->async_unlink_cycle;
check_unlinks_later = true;
- } else if (temp != 0)
- goto rescan;
+ }
}
}
Index: usb-3.9/drivers/usb/host/ehci-sched.c
===================================================================
--- usb-3.9.orig/drivers/usb/host/ehci-sched.c
+++ usb-3.9/drivers/usb/host/ehci-sched.c
@@ -649,7 +649,8 @@ static void end_unlink_intr(struct ehci_
qh->qh_state = QH_STATE_IDLE;
hw->hw_next = EHCI_LIST_END(ehci);
- qh_completions(ehci, qh);
+ if (!list_empty(&qh->qtd_list))
+ qh_completions(ehci, qh);
/* reschedule QH iff another request is queued */
if (!list_empty(&qh->qtd_list) && ehci->rh_state == EHCI_RH_RUNNING) {
@@ -914,7 +915,7 @@ static void scan_intr(struct ehci_hcd *e
list_for_each_entry_safe(qh, ehci->qh_scan_next, &ehci->intr_qh_list,
intr_node) {
- rescan:
+
/* clean any finished work for this qh */
if (!list_empty(&qh->qtd_list)) {
int temp;
@@ -927,12 +928,9 @@ static void scan_intr(struct ehci_hcd *e
* in qh_unlink_periodic().
*/
temp = qh_completions(ehci, qh);
- if (unlikely(qh->needs_rescan ||
- (list_empty(&qh->qtd_list) &&
- qh->qh_state == QH_STATE_LINKED)))
+ if (unlikely(temp || (list_empty(&qh->qtd_list) &&
+ qh->qh_state == QH_STATE_LINKED)))
start_unlink_intr(ehci, qh);
- else if (temp != 0)
- goto rescan;
}
}
}
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