This patch (as1638) makes several changes to the ehci-hcd driver, all
related to the qh_refresh() function. This function must be called
whenever an idle QH gets linked back into either the async or the
periodic schedule.
Change a BUG_ON() in the qh_update routine to a WARN_ON().
Since this code runs in atomic context, a BUG_ON() would
immediately freeze the whole system.
Remove two unneeded calls to qh_refresh(), one when a QH is
initialized and one when a QH becomes idle. Adjust the
adjacent comments accordingly.
Move the qh_refresh() and qh_link_periodic() calls for new
interrupt URBs to after the new TDs have been added.
As a result of the previous two changes, qh_refresh() is never
called when the qtd_list is empty. The corresponding check in
qh_refresh() can be removed, along with an indentation level.
These changes should not cause any alteration of behavior.
Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
---
drivers/usb/host/ehci-q.c | 52 ++++++++++++++++--------------------------
drivers/usb/host/ehci-sched.c | 9 ++++---
2 files changed, 26 insertions(+), 35 deletions(-)
Index: usb-3.8/drivers/usb/host/ehci-q.c
===================================================================
--- usb-3.8.orig/drivers/usb/host/ehci-q.c
+++ usb-3.8/drivers/usb/host/ehci-q.c
@@ -90,7 +90,7 @@ qh_update (struct ehci_hcd *ehci, struct
struct ehci_qh_hw *hw = qh->hw;
/* writes to an active overlay are unsafe */
- BUG_ON(qh->qh_state != QH_STATE_IDLE);
+ WARN_ON(qh->qh_state != QH_STATE_IDLE);
hw->hw_qtd_next = QTD_NEXT(ehci, qtd->qtd_dma);
hw->hw_alt_next = EHCI_LIST_END(ehci);
@@ -123,26 +123,19 @@ qh_refresh (struct ehci_hcd *ehci, struc
{
struct ehci_qtd *qtd;
- if (list_empty (&qh->qtd_list))
- qtd = qh->dummy;
- else {
- qtd = list_entry (qh->qtd_list.next,
- struct ehci_qtd, qtd_list);
- /*
- * first qtd may already be partially processed.
- * If we come here during unlink, the QH overlay region
- * might have reference to the just unlinked qtd. The
- * qtd is updated in qh_completions(). Update the QH
- * overlay here.
- */
- if (qh->hw->hw_token & ACTIVE_BIT(ehci)) {
- qh->hw->hw_qtd_next = qtd->hw_next;
- qtd = NULL;
- }
- }
+ qtd = list_entry(qh->qtd_list.next, struct ehci_qtd, qtd_list);
- if (qtd)
- qh_update (ehci, qh, qtd);
+ /*
+ * first qtd may already be partially processed.
+ * If we come here during unlink, the QH overlay region
+ * might have reference to the just unlinked qtd. The
+ * qtd is updated in qh_completions(). Update the QH
+ * overlay here.
+ */
+ if (qh->hw->hw_token & ACTIVE_BIT(ehci))
+ qh->hw->hw_qtd_next = qtd->hw_next;
+ else
+ qh_update(ehci, qh, qtd);
}
/*-------------------------------------------------------------------------*/
@@ -553,12 +546,9 @@ qh_completions (struct ehci_hcd *ehci, s
* overlaying the dummy qtd (which reduces DMA chatter).
*/
if (stopped != 0 || hw->hw_qtd_next == EHCI_LIST_END(ehci)) {
- switch (state) {
- case QH_STATE_IDLE:
- qh_refresh(ehci, qh);
- break;
- case QH_STATE_LINKED:
- /* We won't refresh a QH that's linked (after the HC
+ if (state == QH_STATE_LINKED) {
+ /*
+ * We won't refresh a QH that's linked (after the HC
* stopped the queue). That avoids a race:
* - HC reads first part of QH;
* - CPU updates that first part and the token;
@@ -568,13 +558,12 @@ qh_completions (struct ehci_hcd *ehci, s
*
* That should be rare for interrupt transfers,
* except maybe high bandwidth ...
+ *
+ * Therefore tell the caller to start an unlink.
*/
-
- /* Tell the caller to start an unlink */
qh->needs_rescan = 1;
- break;
- /* otherwise, unlink already started */
}
+ /* otherwise, unlink already started */
}
return count;
@@ -957,14 +946,13 @@ done:
/* NOTE: if (PIPE_INTERRUPT) { scheduler sets s-mask } */
- /* init as live, toggle clear, advance to dummy */
+ /* init as live, toggle clear */
qh->qh_state = QH_STATE_IDLE;
hw = qh->hw;
hw->hw_info1 = cpu_to_hc32(ehci, info1);
hw->hw_info2 = cpu_to_hc32(ehci, info2);
qh->is_out = !is_input;
usb_settoggle (urb->dev, usb_pipeendpoint (urb->pipe), !is_input, 1);
- qh_refresh (ehci, qh);
return qh;
}
Index: usb-3.8/drivers/usb/host/ehci-sched.c
===================================================================
--- usb-3.8.orig/drivers/usb/host/ehci-sched.c
+++ usb-3.8/drivers/usb/host/ehci-sched.c
@@ -792,7 +792,6 @@ static int qh_schedule(struct ehci_hcd *
unsigned frame; /* 0..(qh->period - 1), or NO_FRAME */
struct ehci_qh_hw *hw = qh->hw;
- qh_refresh(ehci, qh);
hw->hw_next = EHCI_LIST_END(ehci);
frame = qh->start;
@@ -844,8 +843,6 @@ static int qh_schedule(struct ehci_hcd *
} else
ehci_dbg (ehci, "reused qh %p schedule\n", qh);
- /* stuff into the periodic schedule */
- qh_link_periodic(ehci, qh);
done:
return status;
}
@@ -891,6 +888,12 @@ static int intr_submit (
qh = qh_append_tds(ehci, urb, qtd_list, epnum, &urb->ep->hcpriv);
BUG_ON (qh == NULL);
+ /* stuff into the periodic schedule */
+ if (qh->qh_state == QH_STATE_IDLE) {
+ qh_refresh(ehci, qh);
+ qh_link_periodic(ehci, qh);
+ }
+
/* ... update usbfs periodic stats */
ehci_to_hcd(ehci)->self.bandwidth_int_reqs++;
--
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