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Subject[PATCH] PCI: Do not restore firmware BAR assignments behind a PCI-PCI bridge
Fix an issue with the Tyan Tomcat IV S1564D system, the BIOS of which 
does not assign PCI buses beyond #2, where our resource reallocation
code preserves the reset default of an I/O BAR assignment outside its
upstream PCI-to-PCI bridge's I/O forwarding range for device 06:08.0 in
this log:

pci_bus 0000:00: max bus depth: 4 pci_try_num: 5
[...]
pci 0000:06:08.0: BAR 4: no space for [io size 0x0020]
pci 0000:06:08.0: BAR 4: trying firmware assignment [io 0xfce0-0xfcff]
pci 0000:06:08.0: BAR 4: assigned [io 0xfce0-0xfcff]
pci 0000:06:08.1: BAR 4: no space for [io size 0x0020]
pci 0000:06:08.1: BAR 4: trying firmware assignment [io 0xfce0-0xfcff]
pci 0000:06:08.1: BAR 4: [io 0xfce0-0xfcff] conflicts with 0000:06:08.0 [io 0xfce0-0xfcff]
pci 0000:06:08.1: BAR 4: failed to assign [io size 0x0020]
pci 0000:05:00.0: PCI bridge to [bus 06]
pci 0000:05:00.0: bridge window [mem 0xd8000000-0xd85fffff]
[...]
pci 0000:00:11.0: PCI bridge to [bus 01-06]
pci 0000:00:11.0: bridge window [io 0xe000-0xefff]
pci 0000:00:11.0: bridge window [mem 0xd8000000-0xdfffffff]
pci 0000:00:11.0: bridge window [mem 0xa8000000-0xafffffff 64bit pref]
pci_bus 0000:00: No. 2 try to assign unassigned res
[...]
pci 0000:06:08.1: BAR 4: no space for [io size 0x0020]
pci 0000:06:08.1: BAR 4: trying firmware assignment [io 0xfce0-0xfcff]
pci 0000:06:08.1: BAR 4: [io 0xfce0-0xfcff] conflicts with 0000:06:08.0 [io 0xfce0-0xfcff]
pci 0000:06:08.1: BAR 4: failed to assign [io size 0x0020]
pci 0000:05:00.0: PCI bridge to [bus 06]
pci 0000:05:00.0: bridge window [mem 0xd8000000-0xd85fffff]
[...]
pci 0000:00:11.0: PCI bridge to [bus 01-06]
pci 0000:00:11.0: bridge window [io 0xe000-0xefff]
pci 0000:00:11.0: bridge window [mem 0xd8000000-0xdfffffff]
pci 0000:00:11.0: bridge window [mem 0xa8000000-0xafffffff 64bit pref]
pci_bus 0000:00: No. 3 try to assign unassigned res
pci 0000:00:11.0: resource 7 [io 0xe000-0xefff] released
[...]
pci 0000:06:08.1: BAR 4: assigned [io 0x2000-0x201f]
pci 0000:05:00.0: PCI bridge to [bus 06]
pci 0000:05:00.0: bridge window [io 0x2000-0x2fff]
pci 0000:05:00.0: bridge window [mem 0xd8000000-0xd85fffff]
[...]
pci 0000:00:11.0: PCI bridge to [bus 01-06]
pci 0000:00:11.0: bridge window [io 0x1000-0x2fff]
pci 0000:00:11.0: bridge window [mem 0xd8000000-0xdfffffff]
pci 0000:00:11.0: bridge window [mem 0xa8000000-0xafffffff 64bit pref]
pci_bus 0000:00: resource 4 [io 0x0000-0xffff]
pci_bus 0000:00: resource 5 [mem 0x00000000-0xffffffff]
pci_bus 0000:01: resource 0 [io 0x1000-0x2fff]
pci_bus 0000:01: resource 1 [mem 0xd8000000-0xdfffffff]
pci_bus 0000:01: resource 2 [mem 0xa8000000-0xafffffff 64bit pref]
pci_bus 0000:02: resource 0 [io 0x1000-0x2fff]
pci_bus 0000:02: resource 1 [mem 0xd8000000-0xd8bfffff]
pci_bus 0000:04: resource 0 [io 0x1000-0x1fff]
pci_bus 0000:04: resource 1 [mem 0xd8600000-0xd8afffff]
pci_bus 0000:05: resource 0 [io 0x2000-0x2fff]
pci_bus 0000:05: resource 1 [mem 0xd8000000-0xd85fffff]
pci_bus 0000:06: resource 0 [io 0x2000-0x2fff]
pci_bus 0000:06: resource 1 [mem 0xd8000000-0xd85fffff]

-- note that the assignment of 0xfce0-0xfcff is outside the range of
0x2000-0x2fff assigned to bus #6:

05:00.0 PCI bridge: Texas Instruments XIO2000(A)/XIO2200A PCI Express-to-PCI Bridge (rev 03) (prog-if 00 [Normal decode])
Flags: bus master, fast devsel, latency 0
Bus: primary=05, secondary=06, subordinate=06, sec-latency=0
I/O behind bridge: 00002000-00002fff
Memory behind bridge: d8000000-d85fffff
Capabilities: [50] Power Management version 2
Capabilities: [60] Message Signalled Interrupts: 64bit+ Queue=0/4 Enable-
Capabilities: [80] #0d [0000]
Capabilities: [90] Express PCI/PCI-X Bridge IRQ 0

06:08.0 USB controller: VIA Technologies, Inc. VT82xx/62xx/VX700/8x0/900 UHCI USB 1.1 Controller (rev 61) (prog-if 00 [UHCI])
Subsystem: VIA Technologies, Inc. VT82xx/62xx/VX700/8x0/900 UHCI USB 1.1 Controller
Flags: bus master, medium devsel, latency 22, IRQ 5
I/O ports at fce0 [size=32]
Capabilities: [80] Power Management version 2

06:08.1 USB controller: VIA Technologies, Inc. VT82xx/62xx/VX700/8x0/900 UHCI USB 1.1 Controller (rev 61) (prog-if 00 [UHCI])
Subsystem: VIA Technologies, Inc. VT82xx/62xx/VX700/8x0/900 UHCI USB 1.1 Controller
Flags: bus master, medium devsel, latency 22, IRQ 5
I/O ports at 2000 [size=32]
Capabilities: [80] Power Management version 2

Since both 06:08.0 and 06:08.1 have the same reset defaults the latter
device escapes its fate and gets a good assignment owing to an address
conflict with the former device.

Consequently when the device driver tries to access 06:08.0 according to
its designated address range it pokes at an unassigned I/O location,
likely subtractively decoded by the southbridge and forwarded to ISA,
causing the driver to become confused and bail out:

uhci_hcd 0000:06:08.0: host system error, PCI problems?
uhci_hcd 0000:06:08.0: host controller process error, something bad happened!
uhci_hcd 0000:06:08.0: host controller halted, very bad!
uhci_hcd 0000:06:08.0: HCRESET not completed yet!
uhci_hcd 0000:06:08.0: HC died; cleaning up

if good luck happens or if bad luck does, an infinite flood of messages:

uhci_hcd 0000:06:08.0: host system error, PCI problems?
uhci_hcd 0000:06:08.0: host controller process error, something bad happened!
uhci_hcd 0000:06:08.0: host system error, PCI problems?
uhci_hcd 0000:06:08.0: host controller process error, something bad happened!
uhci_hcd 0000:06:08.0: host system error, PCI problems?
uhci_hcd 0000:06:08.0: host controller process error, something bad happened!
[...]

making the system virtually unusuable.

This is because we have code to deal with a situation from PR #16263,
where broken ACPI firmware reports the wrong address range for the host
bridge's decoding window and trying to adjust to the window causes more
breakage than leaving the BIOS assignments intact.

This may work for a device directly on the root bus decoded by the host
bridge only, but for a device behind one or more PCI-to-PCI (or CardBus)
bridges those bridges' forwarding windows have been standardised and
need to be respected, or leaving whatever has been there in a downstream
device's BAR will have no effect as cycles for the addresses recorded
there will have no chance to appear on the bus the device has been
immediately attached to.

Do not restore the firmware assignment for a device behind a PCI-to-PCI
bridge then, fixing the system concerned as follows:

pci_bus 0000:00: max bus depth: 4 pci_try_num: 5
[...]
pci 0000:06:08.0: BAR 4: no space for [io size 0x0020]
pci 0000:06:08.0: BAR 4: failed to assign [io size 0x0020]
pci 0000:06:08.1: BAR 4: no space for [io size 0x0020]
pci 0000:06:08.1: BAR 4: failed to assign [io size 0x0020]
[...]
pci_bus 0000:00: No. 2 try to assign unassigned res
[...]
pci 0000:06:08.0: BAR 4: no space for [io size 0x0020]
pci 0000:06:08.0: BAR 4: failed to assign [io size 0x0020]
pci 0000:06:08.1: BAR 4: no space for [io size 0x0020]
pci 0000:06:08.1: BAR 4: failed to assign [io size 0x0020]
[...]
pci_bus 0000:00: No. 3 try to assign unassigned res
[...]
pci 0000:06:08.0: BAR 4: assigned [io 0x2000-0x201f]
pci 0000:06:08.1: BAR 4: assigned [io 0x2020-0x203f]

and making device 06:08.0 work correctly.

Cf. <https://bugzilla.kernel.org/show_bug.cgi?id=16263>

Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk>
Fixes: 58c84eda0756 ("PCI: fall back to original BIOS BAR addresses")
Cc: stable@vger.kernel.org # v2.6.35+
---
For the record the system's bus topology is as follows:

-[0000:00]-+-00.0
+-07.0
+-07.1
+-07.2
+-11.0-[0000:01-06]----00.0-[0000:02-06]--+-00.0-[0000:03]--
| +-01.0-[0000:04]--+-00.0
| | \-00.3
| \-02.0-[0000:05-06]----00.0-[0000:06]--+-05.0
| +-08.0
| +-08.1
| \-08.2
+-12.0
+-13.0
\-14.0
---
drivers/pci/setup-res.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

linux-pci-setup-res-fw-address-nobridge.diff
Index: linux-macro-ide-tty/drivers/pci/setup-res.c
===================================================================
--- linux-macro-ide-tty.orig/drivers/pci/setup-res.c
+++ linux-macro-ide-tty/drivers/pci/setup-res.c
@@ -328,13 +328,15 @@ int pci_assign_resource(struct pci_dev *
ret = _pci_assign_resource(dev, resno, size, align);

/*
- * If we failed to assign anything, let's try the address
- * where firmware left it. That at least has a chance of
- * working, which is better than just leaving it disabled.
+ * If we failed to assign anything and we're not behind a P2P
+ * or CardBus bridge, let's try the address where firmware
+ * left it. That at least has a chance of working, which is
+ * better than just leaving it disabled.
*/
if (ret < 0) {
pci_info(dev, "BAR %d: no space for %pR\n", resno, res);
- ret = pci_revert_fw_address(res, dev, resno, size);
+ if (!dev->bus->parent)
+ ret = pci_revert_fw_address(res, dev, resno, size);
}

if (ret < 0) {
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