From 6402c796d3b4205d3d7296157956c5100a05d7d6 Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Fri, 1 Mar 2013 10:50:08 -0500 Subject: USB: EHCI: work around silicon bug in Intel's EHCI controllers This patch (as1660) works around a hardware problem present in some (if not all) Intel EHCI controllers. After a QH has been unlinked from the async schedule and the corresponding IAA interrupt has occurred, the controller is not supposed access the QH and its qTDs. There certainly shouldn't be any more DMA writes to those structures. Nevertheless, Intel's controllers have been observed to perform a final writeback to the QH's overlay region and to the most recent qTD. For more information and a test program to determine whether this problem is present in a particular controller, see http://marc.info/?l=linux-usb&m=135492071812265&w=2 http://marc.info/?l=linux-usb&m=136182570800963&w=2 This patch works around the problem by always waiting for two IAA cycles when unlinking an async QH. The extra IAA delay gives the controller time to perform its final writeback. Surprisingly enough, the effects of this silicon bug have gone undetected until quite recently. More through luck than anything else, it hasn't caused any apparent problems. However, it does interact badly with the path that follows this one, so it needs to be addressed. This is the first part of a fix for the regression reported at: https://bugs.launchpad.net/bugs/1088733 Signed-off-by: Alan Stern Tested-by: Stephen Thirlwall CC: Signed-off-by: Greg Kroah-Hartman --- drivers/usb/host/ehci-hcd.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) (limited to 'drivers/usb/host/ehci-hcd.c') diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c index b416a3fc9959..5726cb144abf 100644 --- a/drivers/usb/host/ehci-hcd.c +++ b/drivers/usb/host/ehci-hcd.c @@ -748,11 +748,9 @@ static irqreturn_t ehci_irq (struct usb_hcd *hcd) /* guard against (alleged) silicon errata */ if (cmd & CMD_IAAD) ehci_dbg(ehci, "IAA with IAAD still set?\n"); - if (ehci->async_iaa) { + if (ehci->async_iaa) COUNT(ehci->stats.iaa); - end_unlink_async(ehci); - } else - ehci_dbg(ehci, "IAA with nothing unlinked?\n"); + end_unlink_async(ehci); } /* remote wakeup [4.3.1] */ -- cgit v1.2.3 From 2a40f324541ee61c22146214349c2ce9f5c30bcf Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Fri, 15 Mar 2013 14:40:26 -0400 Subject: USB: EHCI: fix regression during bus resume This patch (as1663) fixes a regression caused by commit 6e0c3339a6f19d748f16091d0a05adeb1e1f822b (USB: EHCI: unlink one async QH at a time). In order to avoid keeping multiple QHs in an unusable intermediate state, that commit changed unlink_empty_async() so that it unlinks only one empty QH at a time. However, when the EHCI root hub is suspended, _all_ async QHs need to be unlinked. ehci_bus_suspend() used to do this by calling unlink_empty_async(), but now this only unlinks one of the QHs, not all of them. The symptom is that when the root hub is resumed, USB communications don't work for some period of time. This is because ehci-hcd doesn't realize it needs to restart the async schedule; it assumes that because some QHs are already on the schedule, the schedule must be running. The easiest way to fix the problem is add a new function that unlinks all the async QHs when the root hub is suspended. This patch should be applied to all kernels that have the 6e0c3339a6f1 commit. Signed-off-by: Alan Stern Reported-and-tested-by: Adrian Bassett Cc: stable Signed-off-by: Greg Kroah-Hartman --- drivers/usb/host/ehci-hcd.c | 1 + drivers/usb/host/ehci-hub.c | 2 +- drivers/usb/host/ehci-q.c | 13 +++++++++++++ 3 files changed, 15 insertions(+), 1 deletion(-) (limited to 'drivers/usb/host/ehci-hcd.c') diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c index 5726cb144abf..416a6dce5e11 100644 --- a/drivers/usb/host/ehci-hcd.c +++ b/drivers/usb/host/ehci-hcd.c @@ -302,6 +302,7 @@ static void ehci_quiesce (struct ehci_hcd *ehci) static void end_unlink_async(struct ehci_hcd *ehci); static void unlink_empty_async(struct ehci_hcd *ehci); +static void unlink_empty_async_suspended(struct ehci_hcd *ehci); static void ehci_work(struct ehci_hcd *ehci); static void start_unlink_intr(struct ehci_hcd *ehci, struct ehci_qh *qh); static void end_unlink_intr(struct ehci_hcd *ehci, struct ehci_qh *qh); diff --git a/drivers/usb/host/ehci-hub.c b/drivers/usb/host/ehci-hub.c index 4d3b294f203e..7d06e77f6c4f 100644 --- a/drivers/usb/host/ehci-hub.c +++ b/drivers/usb/host/ehci-hub.c @@ -328,7 +328,7 @@ static int ehci_bus_suspend (struct usb_hcd *hcd) ehci->rh_state = EHCI_RH_SUSPENDED; end_unlink_async(ehci); - unlink_empty_async(ehci); + unlink_empty_async_suspended(ehci); ehci_handle_intr_unlinks(ehci); end_free_itds(ehci); diff --git a/drivers/usb/host/ehci-q.c b/drivers/usb/host/ehci-q.c index 5464665f0b6a..23d136904285 100644 --- a/drivers/usb/host/ehci-q.c +++ b/drivers/usb/host/ehci-q.c @@ -1316,6 +1316,19 @@ static void unlink_empty_async(struct ehci_hcd *ehci) } } +/* The root hub is suspended; unlink all the async QHs */ +static void unlink_empty_async_suspended(struct ehci_hcd *ehci) +{ + struct ehci_qh *qh; + + while (ehci->async->qh_next.qh) { + qh = ehci->async->qh_next.qh; + WARN_ON(!list_empty(&qh->qtd_list)); + single_unlink_async(ehci, qh); + } + start_iaa_cycle(ehci, false); +} + /* makes sure the async qh will become idle */ /* caller must own ehci->lock */ -- cgit v1.2.3