linux-kernel - Re: X-Gene: Unhandled fault: synchronous external abort in pci_generic_config

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Date:	Wed, 13 Apr 2016 08:21:01 -0500
From:	Bjorn Helgaas <helgaas@...nel.org>
To:	Sudeep Holla <sudeep.holla@....com>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>, Duc Dang <dhdang@....com>,
	Tanmay Inamdar <tinamdar@....com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	linux-arm <linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: X-Gene: Unhandled fault: synchronous external abort in
 pci_generic_config_read32

On Wed, Apr 13, 2016 at 10:58:18AM +0100, Sudeep Holla wrote:
> Hi,
> 
> (sorry for replying on the old thread, but I found it could be related
> to the issue
> I have now)
> 
> On Tue, Jul 28, 2015 at 10:29 PM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
> > On Tue, Jul 28, 2015 at 10:45:26AM -0700, Duc Dang wrote:
> >> On Tue, Jul 28, 2015 at 9:43 AM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
> >> > On Fri, Jul 24, 2015 at 7:05 PM, Duc Dang <dhdang@....com> wrote:
> >> >> Hi Bjorn,
> >> >>
> >> >> On Fri, Jul 24, 2015 at 3:42 PM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
> >> >>>
> >> >>> I regularly see faults like this on an APM X-Gene:
> >> >>>
> >> >>>   U-Boot 2013.04-mustang_sw_1.14.14 (Dec 16 2014 - 15:59:33)
> >> >>>   CPU0: APM ARM 64-bit Potenza Rev B0 2400MHz PCP 2400MHz
> >> >>>        32 KB ICACHE, 32 KB DCACHE
> >> >>>        SOC 2000MHz IOBAXI 400MHz AXI 250MHz AHB 200MHz GFC 125MHz
> >> >>>   ...
> >> >>>   Unhandled fault: synchronous external abort (0x96000010) at 0xffffff8000110034
> >> >>>   Internal error: : 96000010 [#1] SMP
> >> >>>   Modules linked in:
> >> >>>   CPU: 0 PID: 3723 Comm: ... 4.1.0-smp-DEV #3
> >> >>>   Hardware name: APM X-Gene Mustang board (DT)
> >> >>>   task: ffffffc7dc1a4140 ti: ffffffc7dc118000 task.ti: ffffffc7dc118000
> >> >>>   PC is at pci_generic_config_read32+0x4c/0xb8
> >> >>>   LR is at pci_generic_config_read32+0x40/0xb8
> >> >>>   pc : [<ffffffc00033b90c>] lr : [<ffffffc00033b900>] pstate: 600001c5
> >> >>>   ...
> >> >>>   Call trace:
> >> >>>   [<ffffffc00033b90c>] pci_generic_config_read32+0x4c/0xb8
> >> >>>   [<ffffffc00033bf58>] pci_user_read_config_byte+0x60/0xc4
> >> >>>   [<ffffffc0003496a8>] pci_read_config+0x15c/0x238
> >> >>>   [<ffffffc0002393b4>] sysfs_kf_bin_read+0x68/0xa0
> >> >>>   [<ffffffc00023896c>] kernfs_fop_read+0x9c/0x1ac
> >> >>>   [<ffffffc0001c361c>] __vfs_read+0x44/0x128
> >> >>>   [<ffffffc0001c3e28>] vfs_read+0x84/0x144
> >> >>>   [<ffffffc0001c4764>] SyS_read+0x50/0xb0
> >> >>
> >> >> The log shows kernel gets an exception when trying to access Mellanox
> >> >> card configuration space. This is usually due to suboptimal PCIe
> >> >> SerDes parameters are using in your board, which will cause bad link
> >> >> quality.
> >> >> The PCIe SerDes programming is done in U-Boot, so I suggest you do a
> >> >> U-Boot upgrade to our latest X-Gene U-Boot release.
> >> >
> >> > I installed U-Boot 1.15.12, which I thought was the latest.  I'm still
> >> > seeing this issue regularly, approx once/hour.
> >>
> >> Our latest U-Boot is 1.15.15, but U-Boot 1.15.12 is already a good
> >> version to use. Are you running any PCIe traffic test when the error
> >> happens?
> >
> > Nope, the machine was either idle or running a reboot test; no PCIe stress
> > test or anything.
> >
> 
> Was there any conclusion on this ?
> I am having similar issue[1] on my Juno with sky2 PCIe driver during reboot.

We found that the unhandled faults occurred when using an extender
card.  After removing the extender card, we didn't see the faults any
more.

> [1] http://marc.info/?l=linux-netdev&m=146046999701956&w=2