PCI: work around Stratus ftServer broken PCIe hierarchy

A PCIe downstream port is a P2P bridge.  Its secondary interface is
a link that should lead only to device 0 (unless ARI is enabled)[1], so
we don't probe for non-zero device numbers.

Some Stratus ftServer systems have a PCIe downstream port (02:00.0) that
leads to both an upstream port (03:00.0) and a downstream port (03:01.0),
and 03:01.0 has important devices below it:

  [0000:02]-+-00.0-[03-3c]--+-00.0-[04-09]--...
                            \-01.0-[0a-0d]--+-[USB]
                                            +-[NIC]
                                            +-...

Previously, we didn't enumerate device 03:01.0, so USB and the network
didn't work.  This patch adds a DMI quirk to scan all device numbers,
not just 0, below a downstream port.

Based on a patch by Prarit Bhargava.

[1] PCIe spec r3.0, sec 7.3.1

CC: Myron Stowe <mstowe@redhat.com>
CC: Don Dutile <ddutile@redhat.com>
CC: James Paradis <james.paradis@stratus.com>
CC: Matthew Wilcox <matthew.r.wilcox@intel.com>
CC: Jesse Barnes <jbarnes@virtuousgeek.org>
CC: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/asm-generic/pci-bridge.h b/include/asm-generic/pci-bridge.h
index a5b5d5a89a4f..20db2e5a0a69 100644
--- a/include/asm-generic/pci-bridge.h
+++ b/include/asm-generic/pci-bridge.h
@@ -30,6 +30,12 @@ enum {
         PCI_ENABLE_PROC_DOMAINS = 0x00000010,
         /* ... except for domain 0 */
         PCI_COMPAT_DOMAIN_0     = 0x00000020,
+
+        /* PCIe downstream ports are bridges that normally lead to only a
+         * device 0, but if this is set, we scan all possible devices, not
+         * just device 0.
+         */
+        PCI_SCAN_ALL_PCIE_DEVS  = 0x00000040,
 };
 
 #ifdef CONFIG_PCI