Re: [PATCH 1/3] powerpc/mpc85xx: remove the unneeded pci init functions for corenet ds board

Tue, 23 Jul 2013 15:33:40 -0700 

On 06/06/2013 09:00:20 PM, Kevin Hao wrote:

On Mon, Jun 03, 2013 at 11:42:03AM -0500, Scott Wood wrote:
> On 06/01/2013 07:07:20 PM, Kevin Hao wrote:
> >On Sat, Jun 01, 2013 at 09:47:16PM +1000, Benjamin Herrenschmidt
> >wrote:
> >> On Sat, 2013-06-01 at 18:59 +0800, Kevin Hao wrote:
> >>
> >> > The effect of this change is that the isa_io_base will be 0
> >and the IO
> >> > resource are equal to the virtual address of the IO space. But
> >the IO
> >> > functions such as outx/inx should work as well. This is why I
> >ask the
> >> > above question. What do you think about this? Are there any
> >subtle bugs
> >> > that will be triggered by this?
> >>
> >> I don't see any obvious reason why that wouldn't work but like
> >anything
> >> in that area, it needs a bit of testing & hammering to be sure ;-) 
> >
> >Agreed.
>
> Please include QEMU in your testing, as that was where breakage was
> observed that caused us to add the default primary.

I tested this on a qemu with the following command:
  ./qemu-system-ppc -m 1024 -nographic -M ppce500 -kernel ./uImage \
  -initrd /root/initrd.gz \
-append "root=/dev/ram rw console=ttyS0,115200 ramdisk_size=0x60000" \ 
  -cpu e500mc -machine dt_compatible=fsl,,P4080DS

Before applying my patch:
  PCI: Probing PCI hardware
  fsl-pci e0008000.pci: PCI host bridge to bus 0000:00
  pci_bus 0000:00: root bus resource [io  0x0000-0xffff]
  pci_bus 0000:00: root bus resource [mem 0xc0000000-0xdfffffff]
  pci_bus 0000:00: root bus resource [bus 00-ff]
  pci_bus 0000:00: busn_res: [bus 00-ff] end is updated to ff
  pci 0000:00:00.0: [1957:0030] type 01 class 0x060400
  pci 0000:00:00.0: reg 10: [mem 0xfff00000-0xffffffff]
  pci 0000:00:01.0: [1af4:1000] type 00 class 0x020000
  pci 0000:00:01.0: reg 10: [io  0x0000-0x001f]
  pci 0000:00:01.0: reg 14: [mem 0x00000000-0x00000fff]
pci 0000:00:00.0: bridge configuration invalid ([bus 00-00]), reconfiguring 
  pci 0000:00:00.0: PCI bridge to [bus 01-ff]
  pci 0000:00:00.0:   bridge window [io  0x0000-0x0fff]
  pci 0000:00:00.0:   bridge window [mem 0x00000000-0x000fffff]
  pci 0000:00:00.0:   bridge window [mem 0x00000000-0x000fffff pref]
  pci_bus 0000:01: busn_res: [bus 01-ff] end is updated to 01
  pci_bus 0000:00: busn_res: [bus 00-ff] end is updated to 01
PCI: Cannot allocate resource region 0 of device 0000:00:00.0, will remap 
  PCI 0000:00 Cannot reserve Legacy IO [io  0x0000-0x0fff]
  pci 0000:00:00.0: BAR 0: assigned [mem 0xc0000000-0xc00fffff]
  pci 0000:00:00.0: BAR 8: assigned [mem 0xc0100000-0xc01fffff]
  pci 0000:00:01.0: BAR 1: assigned [mem 0xc0200000-0xc0200fff]
  pci 0000:00:01.0: BAR 0: assigned [io  0x1000-0x101f]
  pci 0000:00:00.0: PCI bridge to [bus 01]
  pci 0000:00:00.0:   bridge window [io  0x0000-0x0fff]
  pci 0000:00:00.0:   bridge window [mem 0xc0100000-0xc01fffff]
  pci_bus 0000:00: resource 4 [io  0x0000-0xffff]
  pci_bus 0000:00: resource 5 [mem 0xc0000000-0xdfffffff]
  pci_bus 0000:01: resource 0 [io  0x0000-0x0fff]
  pci_bus 0000:01: resource 1 [mem 0xc0100000-0xc01fffff]

  # lspci -vvv
00:00.0 PCI bridge: Freescale Semiconductor Inc MPC8533E (prog-if 00 [Normal decode]) Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx- Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx- 
          Latency: 0
Region 0: Memory at c0000000 (32-bit, non-prefetchable) [size=1M] 
          Bus: primary=00, secondary=00, subordinate=00, sec-latency=0
          I/O behind bridge: 00000000-00000fff
          Memory behind bridge: 00000000-000fffff
          Prefetchable memory behind bridge: 00000000-000fffff
Secondary status: 66MHz- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- <SERR- <PERR- BridgeCtl: Parity- SERR- NoISA- VGA- MAbort- >Reset- FastB2B- 
                  PriDiscTmr- SecDiscTmr- DiscTmrStat- DiscTmrSERREn-

  00:01.0 Ethernet controller: Red Hat, Inc Virtio network device
          Subsystem: Red Hat, Inc Device 0001
Control: I/O- Mem- BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx- Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx- 
          Interrupt: pin A routed to IRQ 17
          Region 0: I/O ports at 1000 [disabled] [size=32]
Region 1: Memory at c0200000 (32-bit, non-prefetchable) [disabled] [size=4K] 
          Capabilities: [40] MSI-X: Enable- Count=3 Masked-
                  Vector table: BAR=1 offset=00000000
                  PBA: BAR=1 offset=00000800

After applying my patch:
  PCI: Probing PCI hardware
  fsl-pci e0008000.pci: PCI host bridge to bus 0000:00
pci_bus 0000:00: root bus resource [io 0xf1020000-0xf102ffff] (bus address [0x0000-0xffff]) 
  pci_bus 0000:00: root bus resource [mem 0xc0000000-0xdfffffff]
  pci_bus 0000:00: root bus resource [bus 00-ff]
  pci_bus 0000:00: busn_res: [bus 00-ff] end is updated to ff
  pci 0000:00:00.0: [1957:0030] type 01 class 0x060400
  pci 0000:00:00.0: reg 10: [mem 0xfff00000-0xffffffff]
  pci 0000:00:01.0: [1af4:1000] type 00 class 0x020000
  pci 0000:00:01.0: reg 10: [io  0xf1020000-0xf102001f]
  pci 0000:00:01.0: reg 14: [mem 0x00000000-0x00000fff]
pci 0000:00:00.0: bridge configuration invalid ([bus 00-00]), reconfiguring 
  pci 0000:00:00.0: PCI bridge to [bus 01-ff]
  pci 0000:00:00.0:   bridge window [io  0xf1020000-0xf1020fff]
  pci 0000:00:00.0:   bridge window [mem 0x00000000-0x000fffff]
  pci 0000:00:00.0:   bridge window [mem 0x00000000-0x000fffff pref]
  pci_bus 0000:01: busn_res: [bus 01-ff] end is updated to 01
  pci_bus 0000:00: busn_res: [bus 00-ff] end is updated to 01
PCI: Cannot allocate resource region 0 of device 0000:00:00.0, will remap PCI: Cannot allocate resource region 0 of device 0000:00:01.0, will remap 
  PCI 0000:00 Cannot reserve Legacy IO [io  0xf1020000-0xf1020fff]
  pci 0000:00:00.0: BAR 0: assigned [mem 0xc0000000-0xc00fffff]
  pci 0000:00:00.0: BAR 8: assigned [mem 0xc0100000-0xc01fffff]
  pci 0000:00:01.0: BAR 1: assigned [mem 0xc0200000-0xc0200fff]
  pci 0000:00:01.0: BAR 0: assigned [io  0xf1021000-0xf102101f]
  pci 0000:00:00.0: PCI bridge to [bus 01]
  pci 0000:00:00.0:   bridge window [io  0xf1020000-0xf1020fff]
  pci 0000:00:00.0:   bridge window [mem 0xc0100000-0xc01fffff]
  pci_bus 0000:00: resource 4 [io  0xf1020000-0xf102ffff]
  pci_bus 0000:00: resource 5 [mem 0xc0000000-0xdfffffff]
  pci_bus 0000:01: resource 0 [io  0xf1020000-0xf1020fff]
  pci_bus 0000:01: resource 1 [mem 0xc0100000-0xc01fffff]

  # lspci -vvv
00:00.0 PCI bridge: Freescale Semiconductor Inc MPC8533E (prog-if 00 [Normal decode]) Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx- Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx- 
          Latency: 0
Region 0: Memory at c0000000 (32-bit, non-prefetchable) [size=1M] 
          Bus: primary=00, secondary=00, subordinate=00, sec-latency=0
          I/O behind bridge: 00000000-00000fff
          Memory behind bridge: 00000000-000fffff
          Prefetchable memory behind bridge: 00000000-000fffff
Secondary status: 66MHz- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- <SERR- <PERR- BridgeCtl: Parity- SERR- NoISA- VGA- MAbort- >Reset- FastB2B- 
                  PriDiscTmr- SecDiscTmr- DiscTmrStat- DiscTmrSERREn-

  00:01.0 Ethernet controller: Red Hat, Inc Virtio network device
          Subsystem: Red Hat, Inc Device 0001
Control: I/O- Mem- BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx- Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx- 
          Interrupt: pin A routed to IRQ 17
          Region 0: I/O ports at 1000 [disabled] [size=32]
Region 1: Memory at c0200000 (32-bit, non-prefetchable) [disabled] [size=4K] 
          Capabilities: [40] MSI-X: Enable- Count=3 Masked-
                  Vector table: BAR=1 offset=00000000
                  PBA: BAR=1 offset=00000800


As you can see, the only difference between these two logs is the
io resource address and all the mem and bus address are still the
same.
I dug a bit deeper into this, and it's making by head hurt. It seems that we're now getting saved by the host bridge (that for some reason has the class code of a PCI-to-PCI bridge rather than a host bridge) having I/O space of 0x1000 bytes[1], which gets allocated at zero. There have been some changes in the QEMU PCI code since I saw the problem, including changing the class code of the bridge, so that's probably why it sort-of works now.
What QEMU is doing does not match what real hardware does, though. At least on mpc8536 which is similar to mpc8544 (I wasn't able to quickly get access to a working mpc8544 to test on), the PCI bridge has class code Processor, rather than bridge of any sort. Thus, on real hardware we would not get the 0x1000 reservation. What hardware does seems broken to me (when PCI is configured as a host rather than as an endpoint), but so does calling a host bridge a PCI-to-PCI bridge, and so does relying on this mess (not that the primary-bus hack is much better...).
Note that in the case of PCIe -- but not PCI -- Linux has a quirk that relabels the "Processor" on FSL chips as a PCI-to-PCI bridge. Despite the "Processor" labelling, Freescale PCIe (but not PCI) devices appear to have a type 1 config space layout in host mode. I guess this is considered to be the virtual root port. 

-Scott
[1] Really, it's the bridge not having any I/O, but this is how an I/O base/limit of zero are interpreted. 
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