From 2456b97f0c9411d0bc2637ba1033a910c8b4b971 Mon Sep 17 00:00:00 2001 From: Stephen Warren <swarren@nvidia.com> Date: Fri, 7 Feb 2014 09:53:50 -0700 Subject: [PATCH] ush: ehci: initialize altnext pointers in QH MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Section 4.10.2 "Advance Queue" of ehci-specification-for-usb.pdf specifies how an EHCI controller loads a new QTD for processing if the QH is not already marked as active. It states: ===== If the field Bytes to Transfer is not zero and the T-bit in the Alternate Next qTD Pointer is set to zero, then the host controller uses the Alternate Next qTD Pointer. Otherwise, the host controller uses the Next qTD Pointer. If Next qTD Pointerâs T-bit is set to a one, then the host controller exits this state and uses the horizontal pointer to the next schedule data structure. ===== Hence, we must ensure that the alternate next QTD pointer's T-bit (TERMINATE) is set, so the EHCI controller knows to use the next QTD pointer. Signed-off-by: Stephen Warren <swarren@nvidia.com> --- drivers/usb/host/ehci-hcd.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c index 17187caed4..7068b762d8 100644 --- a/drivers/usb/host/ehci-hcd.c +++ b/drivers/usb/host/ehci-hcd.c @@ -395,6 +395,7 @@ ehci_submit_async(struct usb_device *dev, unsigned long pipe, void *buffer, QH_ENDPT2_UFCMASK(0) | QH_ENDPT2_UFSMASK(0); qh->qh_endpt2 = cpu_to_hc32(endpt); qh->qh_overlay.qt_next = cpu_to_hc32(QT_NEXT_TERMINATE); + qh->qh_overlay.qt_altnext = cpu_to_hc32(QT_NEXT_TERMINATE); tdp = &qh->qh_overlay.qt_next; @@ -1186,6 +1187,7 @@ create_int_queue(struct usb_device *dev, unsigned long pipe, int queuesize, qh->qh_link = QH_LINK_TERMINATE; qh->qh_overlay.qt_next = (uint32_t)td; + qh->qh_overlay.qt_altnext = QT_NEXT_TERMINATE; qh->qh_endpt1 = (0 << 28) | /* No NAK reload (ehci 4.9) */ (usb_maxpacket(dev, pipe) << 16) | /* MPS */ (1 << 14) | -- 2.39.5