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P2041 : PCIe devices' driver causing BUS Error

Question asked by madhur wani on Mar 8, 2016

We're using Pericom's 608GP extender. Using the same, we're able to read the configuration space of the every PCIe device. However, we're not able to access the BAR regions of any device.

Whenever we try to read/write to this BAR regions the same through the kernel driver, we're getting following bus error:


Machine check in kernel mode.

Caused by (from MCSR=a000): Load Error Report

Guarded Load Error Report

Oops: Machine check, sig: 7 [#1]

SMP NR_CPUS=8 CoreNet Generic

Modules linked in: emapci(PO) nfsd exportfs

CPU: 3 PID: 1625 Comm: ddccm Tainted: P           O 3.12.37-rt51+g43cecda #2

task: e911ca30 ti: effd8000 task.ti: e9af8000

NIP: f94bc410 LR: f94ba430 CTR: 00000000

REGS: effd9f10 TRAP: 0204   Tainted: P           O  (3.12.37-rt51+g43cecda)

MSR: 00029002 <CE,EE,ME>  CR: 28002422  XER: 00000000

GPR00: f94ba320 e9af9d10 e911ca30 f94bfc70 00000000 f91fe804 e011f000 00000e01

GPR08: 00020000 00000100 f91fe000 1f541215 c0018350 10024a5c 10100000 00000000

GPR16: 00000001 e96d60f0 00000000 00000000 00000000 00000000 00000000 e9af9e38

GPR24: 00000000 00000000 f94bfc70 00000000 00000000 00000000 00000000 00000000

NIP [f94bc410] ddcReadReg32+0x40/0x80 [emapci]

LR [f94ba430] emapci_open+0x430/0x560 [emapci]

Call Trace:

[e9af9d10] [f94ba320] emapci_open+0x320/0x560 [emapci] (unreliable)

[e9af9d50] [c0101b9c] chrdev_open+0xbc/0x1b0

[e9af9d80] [c00fa9e0] do_dentry_open.isra.15+0x1c0/0x2c0

[e9af9da0] [c00fab0c] finish_open+0x2c/0x60

[e9af9db0] [c010c32c] do_last.isra.46+0x3fc/0xc60

[e9af9e20] [c010cc44] path_openat+0xb4/0x660

[e9af9e80] [c010e160] do_filp_open+0x30/0xb0

[e9af9f00] [c00fbf70] do_sys_open+0x150/0x290

[e9af9f40] [c000fe24] ret_from_syscall+0x0/0x3c

--- Exception: c01 at 0xfef43d0

    LR = 0x100023fc

Instruction dump:

3929fc70 7c691a14 812307f0 752a4000 812300b4 8143001c 40c20028 7c8449d6

54a5103a 7ca52214 7ca55214 7c0004ac <7c602c2c> 0c030000 4c00012c 4e800020

---[ end trace 2a777fae257abea4 ]---


Bus error


We've written the driver in following way:

res = pci_enable_device(pdev);
if (res) {
PERR("pci device enable failed\n");
return -EFAULT;
basePhys = pci_resource_start(pdev,0);
baseLength = pci_resource_len(pdev,0);
if(pci_request_region(pdev,0,DRIVER_NAME)==0) {
PINFO("GOT The Resource\n");
if((pci_resource_flags(pdev,0) & IORESOURCE_MEM) != IORESOURCE_MEM) {
else {
actVirtAddr = (unsigned long) bus_to_virt(basePhys); //for PowerPC p2041 architecture we have to do this function call
//because p2041 supports 36Byte addressing
virtAddress = (unsigned long) ioremap(actVirtAddr,baseLength);
elpc_adc_comm_address = virtAddress;


The PCI Configuration dump is in attachments: