This is a note to let you know that I've just added the patch titled
PCI: Enumerate switches below PCI-to-PCIe bridges
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
pci-enumerate-switches-below-pci-to-pcie-bridges.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 51ebfc92b72b4f7dac1ab45683bf56741e454b8c Mon Sep 17 00:00:00 2001
From: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Date: Wed, 11 Jan 2017 09:11:53 -0600
Subject: PCI: Enumerate switches below PCI-to-PCIe bridges
From: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
commit 51ebfc92b72b4f7dac1ab45683bf56741e454b8c upstream.
A PCI-to-PCIe bridge (a "reverse bridge") has a PCI or PCI-X primary
interface and a PCI Express secondary interface. The PCIe interface is a
Downstream Port that originates a Link. See the "PCI Express to PCI/PCI-X
Bridge Specification", rev 1.0, sections 1.2 and A.6.
The bug report below involves a PCI-to-PCIe bridge and a PCIe switch below
the bridge:
00:1e.0 Intel 82801 PCI Bridge to [bus 01-0a]
01:00.0 Pericom PI7C9X111SL PCIe-to-PCI Reversible Bridge to [bus 02-0a]
02:00.0 Pericom Device 8608 [PCIe Upstream Port] to [bus 03-0a]
03:01.0 Pericom Device 8608 [PCIe Downstream Port] to [bus 0a]
01:00.0 is configured as a PCI-to-PCIe bridge (despite the name printed by
lspci). As we traverse a PCIe hierarchy, device connections alternate
between PCIe Links and internal Switch logic. Previously we did not
recognize that 01:00.0 had a secondary link, so we thought the 02:00.0
Upstream Port *did* have a secondary link. In fact, it's the other way
around: 01:00.0 has a secondary link, and 02:00.0 has internal Switch logic
on its secondary side.
When we thought 02:00.0 had a secondary link, the pci_scan_slot() ->
only_one_child() path assumed 02:00.0 could have only one child, so 03:00.0
was the only possible downstream device. But 03:00.0 doesn't exist, so we
didn't look for any other devices on bus 03.
Booting with "pci=pcie_scan_all" is a workaround, but we don't want users
to have to do that.
Recognize that PCI-to-PCIe bridges originate links on their secondary
interfaces.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=189361
Fixes: d0751b98dfa3 ("PCI: Add dev->has_secondary_link to track downstream PCIe links")
Tested-by: Blake Moore <blake.moore@xxxxxx>
Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/pci/probe.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1050,6 +1050,7 @@ void set_pcie_port_type(struct pci_dev *
pos = pci_find_capability(pdev, PCI_CAP_ID_EXP);
if (!pos)
return;
+
pdev->pcie_cap = pos;
pci_read_config_word(pdev, pos + PCI_EXP_FLAGS, ®16);
pdev->pcie_flags_reg = reg16;
@@ -1057,13 +1058,14 @@ void set_pcie_port_type(struct pci_dev *
pdev->pcie_mpss = reg16 & PCI_EXP_DEVCAP_PAYLOAD;
/*
- * A Root Port is always the upstream end of a Link. No PCIe
- * component has two Links. Two Links are connected by a Switch
- * that has a Port on each Link and internal logic to connect the
- * two Ports.
+ * A Root Port or a PCI-to-PCIe bridge is always the upstream end
+ * of a Link. No PCIe component has two Links. Two Links are
+ * connected by a Switch that has a Port on each Link and internal
+ * logic to connect the two Ports.
*/
type = pci_pcie_type(pdev);
- if (type == PCI_EXP_TYPE_ROOT_PORT)
+ if (type == PCI_EXP_TYPE_ROOT_PORT ||
+ type == PCI_EXP_TYPE_PCIE_BRIDGE)
pdev->has_secondary_link = 1;
else if (type == PCI_EXP_TYPE_UPSTREAM ||
type == PCI_EXP_TYPE_DOWNSTREAM) {
Patches currently in stable-queue which might be from bhelgaas@xxxxxxxxxx are
queue-4.9/x86-pci-ignore-_crs-on-supermicro-x8dth-i-6-if-6f.patch
queue-4.9/pci-designware-check-for-iatu-unroll-only-on-platforms-that-use-atu.patch
queue-4.9/pci-enumerate-switches-below-pci-to-pcie-bridges.patch
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