On Fri, Jul 24, 2015 at 05:05:19PM -0700, Duc Dang wrote:

On Fri, Jul 24, 2015 at 3:42 PM, Bjorn Helgaas [off-list ref] wrote:

quoted

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

That's generated by an external device (PCIe root complex, card etc.)
and some mis-configured CPU setting.

quoted

  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.

I would have hoped that "suboptimal" means that it still works, albeit
not fully optimal ;).

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.

In order to access latest X-Gene U-Boot release, please use APM
official support channel:
https://myapm.apm.com

Please register an account at myapm.apm.com if you don't have one
using following link:
https://myapm.apm.com/user/register

Isn't the latest U-Boot source for X-Gene publicly available anywhere?
It's GPL code anyway, so it shouldn't have proprietary code to require
registration, click-through agreements.

-- 
Catalin