The PCI subsystem always assumes that I/O is supported on PCIe bridges
and tries to assign an I/O window to each child bus 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 bus or its parent does not support
I/O in the first place.
To avoid this message, check if a bus supports I/O before trying to
enable it. Also check if the root bus has an IO window assigned;
if not, it does not make sense to try to assign one to any of its
child busses.
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
---
v2: Use a new bus flag to indicate if IO is supported on a bus or not.
Using IORESOURCE_DISABLED in resource flags turned out to be futile,
since the term "!res->flags" is widely used to detect if a resource
window is enabled or not, and setting IORESOURCE_DISABLED would
affect all this code.
This patch depends on 'PCI: move pci_read_bridge_bases to the generic
PCI layer' by Lorenzo Pieralisi; without it, pci_read_bridge_io()
is not always called.
With this version of the patch, pci_bridge_check_ranges() still sets
IORESOURCE_IO. Moving this into pci_read_bridge_io() had undesirable
side effects and resulted in missing IO window assignments on one of
the x86 platforms I tested with. I'll have to explore this further.
drivers/pci/probe.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
drivers/pci/setup-bus.c | 9 +--------
include/linux/pci.h | 1 +
3 files changed, 48 insertions(+), 8 deletions(-)
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index cefd636681b6..b21cba7aeb79 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -332,6 +332,35 @@ static void pci_read_bases(struct pci_dev *dev, unsigned int howmany, int rom)
}
}
+static bool pci_bus_supports_io(struct pci_bus *bus)
+{
+ struct pci_dev *dev = bus->self;
+ u16 io;
+
+ pci_read_config_word(dev, PCI_IO_BASE, &io);
+ if (!io) {
+ 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);
+ }
+ return !!io;
+}
+
+static bool pci_root_has_io_resource(struct pci_bus *bus)
+{
+ struct resource *res;
+ int i;
+
+ while (bus->parent)
+ bus = bus->parent;
+
+ pci_bus_for_each_resource(bus, res, i) {
+ if (res && (res->flags & IORESOURCE_IO))
+ return true;
+ }
+ return false;
+}
+
static void pci_read_bridge_io(struct pci_bus *child)
{
struct pci_dev *dev = child->self;
@@ -340,6 +369,23 @@ static void pci_read_bridge_io(struct pci_bus *child)
struct pci_bus_region region;
struct resource *res;
+ if (child->bus_flags & PCI_BUS_FLAGS_NO_IO)
+ return;
+
+ if (!pci_bus_supports_io(child)) {
+ dev_printk(KERN_DEBUG, &dev->dev,
+ " bus does not support IO\n");
+ child->bus_flags |= PCI_BUS_FLAGS_NO_IO;
+ return;
+ }
+
+ if (!pci_root_has_io_resource(child)) {
+ dev_printk(KERN_DEBUG, &dev->dev,
+ " no IO window on root bus\n");
+ child->bus_flags |= PCI_BUS_FLAGS_NO_IO;
+ return;
+ }
+
io_mask = PCI_IO_RANGE_MASK;
io_granularity = 0x1000;
if (dev->io_window_1k) {
diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index 508cc56130e3..c8c7eecadbfe 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -744,7 +744,6 @@ int pci_claim_bridge_resource(struct pci_dev *bridge, int i)
base/limit registers must be read-only and read as 0. */
static void pci_bridge_check_ranges(struct pci_bus *bus)
{
- u16 io;
u32 pmem;
struct pci_dev *bridge = bus->self;
struct resource *b_res;
@@ -752,13 +751,7 @@ static void pci_bridge_check_ranges(struct pci_bus *bus)
b_res = &bridge->resource[PCI_BRIDGE_RESOURCES];
b_res[1].flags |= IORESOURCE_MEM;
- pci_read_config_word(bridge, PCI_IO_BASE, &io);
- if (!io) {
- 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 (!(bus->bus_flags & PCI_BUS_FLAGS_NO_IO))
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 8a0321a8fb59..b910ed04aa0b 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -191,6 +191,7 @@ typedef unsigned short __bitwise pci_bus_flags_t;
enum pci_bus_flags {
PCI_BUS_FLAGS_NO_MSI = (__force pci_bus_flags_t) 1,
PCI_BUS_FLAGS_NO_MMRBC = (__force pci_bus_flags_t) 2,
+ PCI_BUS_FLAGS_NO_IO = (__force pci_bus_flags_t) 4,
};
/* These values come from the PCI Express Spec */
--
2.1.0
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