From fc0855f2747a0e21d86b7e63c50bf234fa766184 Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Fri, 20 Nov 2015 13:53:58 -0500 Subject: [PATCH] USB: EHCI: warn on unexpectedly active QH This patch adds a new warning message to ehci-hcd. The warning is triggered whenever the driver finds that the hardware has set the Active bit in a QH at a time when the driver expects the QH to be completely idle. Such bugs have been observed by users in the past, and since they can lead to serious problems (such as inability to unlink an URB that never completes), it would be good to know about them when they occur. This won't fix these bugs; that's a bigger job for a later patch. But success isn't guaranteed, since this depends on aspects of the hardware which are not documented in the EHCI spec or for which the spec's recommendations are clearly unworkable. It therefore seems worthwhile to check for these bugs proactively. Signed-off-by: Alan Stern Reported-by: Michael Reutman Signed-off-by: Greg Kroah-Hartman --- drivers/usb/host/ehci-q.c | 9 +++++++-- drivers/usb/host/ehci.h | 1 + 2 files changed, 8 insertions(+), 2 deletions(-) diff --git a/drivers/usb/host/ehci-q.c b/drivers/usb/host/ehci-q.c index 54f5332f814d..aad0777240d3 100644 --- a/drivers/usb/host/ehci-q.c +++ b/drivers/usb/host/ehci-q.c @@ -132,10 +132,14 @@ qh_refresh (struct ehci_hcd *ehci, struct ehci_qh *qh) * qtd is updated in qh_completions(). Update the QH * overlay here. */ - if (qh->hw->hw_token & ACTIVE_BIT(ehci)) + if (qh->hw->hw_token & ACTIVE_BIT(ehci)) { qh->hw->hw_qtd_next = qtd->hw_next; - else + if (qh->should_be_inactive) + ehci_warn(ehci, "qh %p should be inactive!\n", qh); + } else { qh_update(ehci, qh, qtd); + } + qh->should_be_inactive = 0; } /*-------------------------------------------------------------------------*/ @@ -438,6 +442,7 @@ qh_completions (struct ehci_hcd *ehci, struct ehci_qh *qh) (hw->hw_token & ACTIVE_BIT(ehci))) { token = hc32_to_cpu(ehci, hw->hw_token); hw->hw_token &= ~ACTIVE_BIT(ehci); + qh->should_be_inactive = 1; /* An unlink may leave an incomplete * async transaction in the TT buffer. diff --git a/drivers/usb/host/ehci.h b/drivers/usb/host/ehci.h index 46f62e41bcde..ec61aedb0067 100644 --- a/drivers/usb/host/ehci.h +++ b/drivers/usb/host/ehci.h @@ -439,6 +439,7 @@ struct ehci_qh { unsigned dequeue_during_giveback:1; unsigned exception:1; /* got a fault, or an unlink was requested */ + unsigned should_be_inactive:1; }; /*-------------------------------------------------------------------------*/ -- 2.39.2