Broken PCI on Sequoia

[Geert Uytterhoeven]

	Hi Ben, Josh,

I did some background bisecting to find out when PCI stopped working on the
AMCC EV-440EPX `Sequoia' Reference Board.

With ppc44x_defconfig + CONFIG_USB=y + CONFIG_USB_EHCI_HCD=y and a USB 2.0 PCI
card in one of the PCI slots, I get:

| ehci_hcd: USB 2.0 'Enhanced' Host Controller (EHCI) Driver
| ehci_hcd 0000:00:0a.2: enabling device (0000 -> 0002)
| ehci_hcd 0000:00:0a.2: EHCI Host Controller
| ehci_hcd 0000:00:0a.2: new USB bus registered, assigned bus number 1
| Machine check in kernel mode.
| Data Read PLB Error
| Oops: Machine check, sig: 7 [#1]
| PowerPC 44x Platform
| Modules linked in:
| NIP: c01acf24 LR: c019a2e0 CTR: c01ace34
| REGS: cfff7f10 TRAP: 0214   Not tainted  (2.6.29-rc3)
| MSR: 00029000 <EE,ME,CE>  CR: 28002224  XER: 20000000
| TASK = cf818400[1] 'swapper' THREAD: cf828000
| GPR00: 00000000 cf829d80 cf818400 cf9a8a00 0000002f 00000000 c024dd9c fffffffd 
| GPR08: 00000000 d10a8000 00000000 d10a8000 48002242 1001b1cc 0ffb2400 00000001 
| GPR16: 007fff13 00400458 00800000 ffffffff 007fff00 0ffadd68 00000000 00000001 
| GPR24: 00000000 c0322a88 00000010 000000a0 cf9fd000 cf83a800 cf9a8ab8 cf9a8a00 
| NIP [c01acf24] ehci_pci_setup+0xf0/0x5f0
| LR [c019a2e0] usb_add_hcd+0x1a8/0x5e8
| Call Trace:
| [cf829d80] [cf9a8a00] 0xcf9a8a00 (unreliable)
| [cf829db0] [c019a2e0] usb_add_hcd+0x1a8/0x5e8
| [cf829de0] [c01a59c4] usb_hcd_pci_probe+0x158/0x2e4
| [cf829e10] [c015c0cc] local_pci_probe+0x24/0x34
| [cf829e20] [c015c2f4] pci_device_probe+0x84/0xa8
| [cf829e50] [c017b388] driver_probe_device+0xb4/0x1e8
| [cf829e70] [c017b560] __driver_attach+0xa4/0xa8
| [cf829e90] [c017ab2c] bus_for_each_dev+0x5c/0xb0
| [cf829ec0] [c017b1a4] driver_attach+0x24/0x34
| [cf829ed0] [c017a44c] bus_add_driver+0x1d0/0x244
| [cf829ef0] [c017b780] driver_register+0x70/0x160
| [cf829f10] [c015c59c] __pci_register_driver+0x4c/0xac
| [cf829f30] [c02fb514] ehci_hcd_init+0xb0/0xf0
| [cf829f50] [c00013d8] do_one_initcall+0x34/0x1b0
| [cf829fc0] [c02e1178] kernel_init+0x94/0x100
| [cf829ff0] [c000da64] kernel_thread+0x50/0x6c
| Instruction dump:
| 2f8001b5 409eff68 801e00e0 64002000 901e00e0 74082000 813f008c 7d2b4b78 
| 913f00b8 40a2ff60 7c0004ac 7c004c2c <0c000000> 4c00012c 5400063e 7c0b0214 
| ---[ end trace 1bac7a35c80d2df5 ]---

I get a similar crash with a Sym53c876 SCSI card.

PCI seems to have stopped working between 2.6.28 and 2.6.29-rc1, due to the
following commit:

| commit 84d727a109081684c2e01b811cb0d6dc3b9380ca
| Author: Benjamin Herrenschmidt <benh at kernel.crashing.org>
| Date:   Thu Oct 9 16:58:19 2008 +0000
| 
|     powerpc/4xx: Add support for ISA holes on 4xx PCI/X/E
|     
|     This adds support for ISA memory holes on the PCI, PCI-X and
|     PCI-E busses of the 4xx platforms. The patch includes changes
|     to the Bamboo and Canyonlands device-trees to add such a hole,
|     others can be updated separately.
|     
|     The ISA memory hole is an additional outbound window configured
|     in the bridge to generate PCI cycles in the low memory addresses,
|     thus allowing to access things such as the hard-decoded VGA
|     aperture at 0xa0000..0xbffff or other similar things. It's made
|     accessible to userspace via the new legacy_mem file in sysfs for
|     which support was added by a previous patch.
|     
|     Signed-off-by: Benjamin Herrenschmidt <benh at kernel.crashing.org>
|     Signed-off-by: Josh Boyer <jwboyer at linux.vnet.ibm.com>
| 
|  boot/dts/bamboo.dts      |    3 
|  boot/dts/canyonlands.dts |    3 
|  sysdev/ppc4xx_pci.c      |  306 ++++++++++++++++++++++++++++++---------------
|  3 files changed, 213 insertions(+), 99 deletions(-)

Git-reverting this commit on top of 2.6.29-rc3 makes the crash go away.

Perhaps sequoia.dts (and other 44x DTS files) had to be changed, too?

With kind regards,

Geert Uytterhoeven
Software Architect

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