X-Gene: Unhandled fault: synchronous external abort in pci_generic_config_read32

[Bjorn Helgaas]

On Fri, Jul 24, 2015 at 7:05 PM, Duc Dang <dhdang at apm.com> wrote:
> Hi Bjorn,
>
> On Fri, Jul 24, 2015 at 3:42 PM, Bjorn Helgaas <bhelgaas at google.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.