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++; -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html