linux-kernel - Re: USB Serial device disconnect causes IRQ disable after using ehci controller halted

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Message-Id: <200808261443.47064.david-b@pacbell.net>
Date:	Tue, 26 Aug 2008 14:43:46 -0700
From:	David Brownell <david-b@...bell.net>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Karsten Wiese <fzu@...gehoertderstaat.de>,
	amruth <amruth_pv@...oo.com>, Oliver Neukum <oliver@...kum.org>,
	USB list <linux-usb@...r.kernel.org>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Greg KH <greg@...ah.com>
Subject: Re: USB Serial device disconnect causes IRQ disable after using ehci controller halted

On Tuesday 26 August 2008, Alan Stern wrote:
> While it certainly would be a good idea to prevent the handshake 
> failures from occurring in the first place -- Dave, aren't you working 
> on a patch for that? -- we should also make sure that when they do 
> occur, the controller gets reset properly.  And an error message should 
> be printed in the log.

Like this?

Greg, please queue for 2.6.27 unless someone finds a
problem with this patch.


=========	SNIP!  SNIP!  SNIPPITY SNIP!
From: David Brownell <dbrownell@...rs.sourceforge.net>

I noticed that the "Refactor "if (handshake()) state = HC_STATE_HALT"
patch from earlier this year perpetuated a potential problem:  it can
mark the controller as halted when it's still running (but not acting
as, perhaps wrongly, expected).

That caused some hangs and crashes, rather than more polite failure
modes of a truly halted controller.  This patch forces a true halt,
and emits a (previously missing) diagnostic.

Signed-off-by: David Brownell <dbrownell@...rs.sourceforge.net>
---
 drivers/usb/host/ehci-hcd.c |   26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

--- a/drivers/usb/host/ehci-hcd.c	2008-08-15 14:04:27.000000000 -0700
+++ b/drivers/usb/host/ehci-hcd.c	2008-08-15 14:04:36.000000000 -0700
@@ -145,16 +145,6 @@ static int handshake (struct ehci_hcd *e
 	return -ETIMEDOUT;
 }
 
-static int handshake_on_error_set_halt(struct ehci_hcd *ehci, void __iomem *ptr,
-				       u32 mask, u32 done, int usec)
-{
-	int error = handshake(ehci, ptr, mask, done, usec);
-	if (error)
-		ehci_to_hcd(ehci)->state = HC_STATE_HALT;
-
-	return error;
-}
-
 /* force HC to halt state from unknown (EHCI spec section 2.3) */
 static int ehci_halt (struct ehci_hcd *ehci)
 {
@@ -173,6 +163,22 @@ static int ehci_halt (struct ehci_hcd *e
 			  STS_HALT, STS_HALT, 16 * 125);
 }
 
+static int handshake_on_error_set_halt(struct ehci_hcd *ehci, void __iomem *ptr,
+				       u32 mask, u32 done, int usec)
+{
+	int error;
+
+	error = handshake(ehci, ptr, mask, done, usec);
+	if (error) {
+		ehci_halt(ehci);
+		ehci_to_hcd(ehci)->state = HC_STATE_HALT;
+		ehci_err(ehci, "force halt; handhake %p %08x %08x -> %d\n",
+			ptr, mask, done, error);
+	}
+
+	return error;
+}
+
 /* put TDI/ARC silicon into EHCI mode */
 static void tdi_reset (struct ehci_hcd *ehci)
 {


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