pci: Workaround Stratus broken PCIE hierarchy
Stratus systems have a hierarchy that includes a PCIE Downstream bridge
connected to a PCIE Upstream bridge and a PCI Downstream bridge. The system
boots with this wrong hierarchy into a crippled mode (USB doesn't work,
network doesn't work ...). Avoiding the Downstream bridge check in
only_one_child() causes all the bridges to be enumerated and the system
to function properly.
Unfortunately this hardware is currently available so we should at least
keep it functional.
[v2]
- ddutile@xxxxxxxxxx requested drivers/pci/quirks.c code
- matthew@xxxxxx requested that dmi_name_in_vendors() be called only once with a static var check
- added a kernel parameter to enable scanning of all PCIE devices.
[v3]
- matthew@xxxxxx requested a clean up of is_broken_pcie_port(
- eike-kernel@xxxxxxxxx requested a clean up of the printk level and message
Signed-off-by: Prarit Bhargava <prarit@xxxxxxxxxx>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index a0c5c5f..7af458f 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2069,6 +2069,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
on: Turn ECRC on.
realloc reallocate PCI resources if allocations done by BIOS
are erroneous.
+ pcie_scan_all Scan all possible PCIE devices.
pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
Management.
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 6f45a73..8c96fff 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -3589,6 +3589,9 @@ static int __init pci_setup(char *str)
pcie_bus_config = PCIE_BUS_PERFORMANCE;
} else if (!strncmp(str, "pcie_bus_peer2peer", 18)) {
pcie_bus_config = PCIE_BUS_PEER2PEER;
+ } else if (!strncmp(str, "pcie_scan_all", 13)) {
+ printk(KERN_INFO HW_ERR "PCIE: User request scan of all PCIE devices. Your PCIE hardware is broken if you require this to boot.\n");
+ pcie_scan_all = 1;
} else {
printk(KERN_ERR "PCI: Unknown option `%s'\n",
str);
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index b74084e..5a07895 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -309,11 +309,16 @@ struct pci_dev_reset_methods {
#ifdef CONFIG_PCI_QUIRKS
extern int pci_dev_specific_reset(struct pci_dev *dev, int probe);
+extern int is_broken_pcie_port(void);
#else
static inline int pci_dev_specific_reset(struct pci_dev *dev, int probe)
{
return -ENOTTY;
}
+static inline int is_broken_pcie_port(void)
+{
+ return 0;
+}
#endif
#endif /* DRIVERS_PCI_H */
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 04e74f4..fc88a9b 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1270,13 +1270,18 @@ static unsigned no_next_fn(struct pci_dev *dev, unsigned fn)
return 0;
}
+int pcie_scan_all = 0; /* set via pci=pcie_scan_all */
static int only_one_child(struct pci_bus *bus)
{
struct pci_dev *parent = bus->self;
+ if (pcie_scan_all)
+ return 0;
if (!parent || !pci_is_pcie(parent))
return 0;
- if (parent->pcie_type == PCI_EXP_TYPE_ROOT_PORT ||
- parent->pcie_type == PCI_EXP_TYPE_DOWNSTREAM)
+ if (parent->pcie_type == PCI_EXP_TYPE_ROOT_PORT)
+ return 1;
+ if (parent->pcie_type == PCI_EXP_TYPE_DOWNSTREAM &&
+ !is_broken_pcie_port())
return 1;
return 0;
}
diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index 7285145..704e66d 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -3092,3 +3092,17 @@ int pci_dev_specific_reset(struct pci_dev *dev, int probe)
return -ENOTTY;
}
+
+int is_broken_pcie_port(void)
+{
+ /*
+ * Stratus/NEC ftServer systems have a broken PCIE hierarchy in which
+ * one upstream and one downstream port are plugged into a downstream
+ * port. Avoiding the downstream port check in only_one_child() results
+ * in a functional system.
+ */
+ if (dmi_name_in_vendors("ftServer"))
+ pcie_scan_all = 1;
+
+ return pcie_scan_all;
+}
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 337df0d..745b98e 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1647,5 +1647,7 @@ static inline void pci_release_bus_of_node(struct pci_bus *bus) { }
*/
struct pci_dev *pci_find_upstream_pcie_bridge(struct pci_dev *pdev);
+/* set via pci=pcie_scan_all in order to enumerate all possible PCIE busses */
+extern int pcie_scan_all;
#endif /* __KERNEL__ */
#endif /* LINUX_PCI_H */
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