The PCI subsystem always assumes that I/O is supported on PCIe bridges
and tries to assign an I/O window to each port even if that is not
the case.
This may result in messages such as
pcieport 0000:02:00.0: res[7]=[io 0x1000-0x0fff]
get_res_add_size add_size 1000
pcieport 0000:02:00.0: BAR 7: no space for [io size 0x1000]
pcieport 0000:02:00.0: BAR 7: failed to assign [io size 0x1000]
for each bridge port, even if a port or its parent does not support
I/O in the first place.
To avoid this message, check if a port supports I/O before trying to
enable it. Also check if port's parent supports I/O, and only modify
a port's I/O resource size if both the port and its parent support I/O.
If IO is disabled after the initial port scan, the IO base and size
registers are set to 0x00f0 to indicate that IO is disabled. A later
rescan interprets this as "IO supported" and enables the IO range,
even if the parent does not support IO. Handle this situation as well.
Signed-off-by: Guenter Roeck <li...@roeck-us.net>
---
drivers/pci/probe.c | 14 ++++++++++++++
drivers/pci/setup-bus.c | 4 ++--
include/linux/pci.h | 9 +++++++++
3 files changed, 25 insertions(+), 2 deletions(-)
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 6675a7a1b9fc..f4944ef45148 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -354,6 +354,20 @@ static void pci_read_bridge_io(struct pci_bus *child)
base = (io_base_lo & io_mask) << 8;
limit = (io_limit_lo & io_mask) << 8;
+ /* If necessary, check if the bridge supports an I/O aperture */
+ if (!io_base_lo && !io_limit_lo) {
+ u16 io;
+
+ if (!pci_parent_supports_io(child))
+ return;
+
+ pci_write_config_word(dev, PCI_IO_BASE, 0xe0f0);
+ pci_read_config_word(dev, PCI_IO_BASE, &io);
+ pci_write_config_word(dev, PCI_IO_BASE, 0x0);
+ if (!io)
+ return;
+ }
+
if ((io_base_lo & PCI_IO_RANGE_TYPE_MASK) == PCI_IO_RANGE_TYPE_32) {
u16 io_base_hi, io_limit_hi;
diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index 4fd0cacf7ca0..963b31a109a9 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -750,12 +750,12 @@ static void pci_bridge_check_ranges(struct pci_bus *bus)
b_res[1].flags |= IORESOURCE_MEM;
pci_read_config_word(bridge, PCI_IO_BASE, &io);
- if (!io) {
+ if (!io && pci_parent_supports_io(bus)) {
pci_write_config_word(bridge, PCI_IO_BASE, 0xe0f0);
pci_read_config_word(bridge, PCI_IO_BASE, &io);
pci_write_config_word(bridge, PCI_IO_BASE, 0x0);
}
- if (io)
+ if (io && (io != 0x00f0 || pci_parent_supports_io(bus)))
b_res[0].flags |= IORESOURCE_IO;
/* DECchip 21050 pass 2 errata: the bridge may miss an address
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 353db8dc4c6e..f3de9e24aab1 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -489,6 +489,15 @@ static inline bool pci_is_root_bus(struct pci_bus *pbus)
return !(pbus->parent);
}
+/*
+ * Returns true if the parent bus supports an I/O aperture.
+ */
+static inline bool pci_parent_supports_io(struct pci_bus *pbus)
+{
+ return pci_is_root_bus(pbus) || pci_is_root_bus(pbus->parent) ||
+ (pbus->parent->resource[0]->flags & IORESOURCE_IO);
+}
+
/**
* pci_is_bridge - check if the PCI device is a bridge
* @dev: PCI device
--
2.1.0
--
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