[3.16.y-ckt stable] Patch "PCI: Mark Atheros AR93xx to avoid bus reset" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    PCI: Mark Atheros AR93xx to avoid bus reset

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt6.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 4585429b2a4a5689d1118c47323aa4a927528f5c Mon Sep 17 00:00:00 2001
From: Alex Williamson <alex.williamson at redhat.com>
Date: Thu, 15 Jan 2015 18:17:12 -0600
Subject: PCI: Mark Atheros AR93xx to avoid bus reset

commit c3e59ee4e76686b0c84ca8faa1011d10cd4ca1b8 upstream.

Reports against the TL-WDN4800 card indicate that PCI bus reset of this
Atheros device cause system lock-ups and resets.  I've also been able to
confirm this behavior on multiple systems.  The device never returns from
reset and attempts to access config space of the device after reset result
in hangs.  Blacklist bus reset for the device to avoid this issue.

[bhelgaas: This regression appeared in v3.14.  Andreas bisected it to
425c1b223dac ("PCI: Add Virtual Channel to save/restore support"), but we
don't understand the mechanism by which that commit affects the reset
path.]

[bhelgaas: changelog, references]
Link: http://lkml.kernel.org/r/20140923210318.498dacbd@dualc.maya.org
Reported-by: Andreas Hartmann <andihartmann at freenet.de>
Tested-by: Andreas Hartmann <andihartmann at freenet.de>
Signed-off-by: Alex Williamson <alex.williamson at redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas at google.com>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/pci/quirks.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index cc09b14b8ac1..293d2c2ccc55 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -3006,6 +3006,20 @@ DECLARE_PCI_FIXUP_HEADER(0x1814, 0x0601, /* Ralink RT2800 802.11n PCI */
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_REALTEK, 0x8169,
 			 quirk_broken_intx_masking);

+static void quirk_no_bus_reset(struct pci_dev *dev)
+{
+	dev->dev_flags |= PCI_DEV_FLAGS_NO_BUS_RESET;
+}
+
+/*
+ * Atheros AR93xx chips do not behave after a bus reset.  The device will
+ * throw a Link Down error on AER-capable systems and regardless of AER,
+ * config space of the device is never accessible again and typically
+ * causes the system to hang or reset when access is attempted.
+ * http://www.spinics.net/lists/linux-pci/msg34797.html
+ */
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x0030, quirk_no_bus_reset);
+
 static void pci_do_fixups(struct pci_dev *dev, struct pci_fixup *f,
 			  struct pci_fixup *end)
 {
--
2.1.4