PCI device BARs are guaranteed to start and end on at least a four-byte
(I/O) or a sixteen-byte (MMIO) boundary because they're aligned on their
size and the low BAR bits are reserved. PCI-to-PCI bridge apertures
have even larger alignment restrictions.
However, some BIOSes (e.g., HP DL360 BIOS P31) report host bridge windows
like "[io 0x0000-0x2cfe]". This is wrong because it excludes the last
port at 0x2cff: it's impossible for a downstream device to claim 0x2cfe
without also claiming 0x2cff. In fact, this BIOS configures a device
behind the bridge to "[io 0x2c00-0x2cff]", so we know the window actually
does include 0x2cff.
This patch rounds the start and end of apertures to the appropriate
boundary. I experimentally determined that Windows contains a similar
workaround; details here:
http://bugzilla.kernel.org/show_bug.cgi?id=14337
Signed-off-by: Bjorn Helgaas <bjorn.helgaas@xxxxxx>
---
arch/x86/pci/acpi.c | 25 +++++++++++++++++++++++++
1 files changed, 25 insertions(+), 0 deletions(-)
diff --git a/arch/x86/pci/acpi.c b/arch/x86/pci/acpi.c
index 54db5a0..8ddf4f4 100644
--- a/arch/x86/pci/acpi.c
+++ b/arch/x86/pci/acpi.c
@@ -59,6 +59,30 @@ bus_has_transparent_bridge(struct pci_bus *bus)
return false;
}
+static void
+align_resource(struct acpi_device *bridge, struct resource *res)
+{
+ int align = (res->flags & IORESOURCE_MEM) ? 16 : 4;
+
+ /*
+ * Host bridge windows are not BARs, but the decoders on the PCI side
+ * that claim this address space have starting alignment and length
+ * constraints, so fix any obvious BIOS goofs.
+ */
+ if (res->start & (align - 1)) {
+ dev_printk(KERN_DEBUG, &bridge->dev,
+ "host bridge window %pR invalid; "
+ "aligning start to %d-byte boundary\n", res, align);
+ res->start &= ~(align - 1);
+ }
+ if ((res->end + 1) & (align - 1)) {
+ dev_printk(KERN_DEBUG, &bridge->dev,
+ "host bridge window %pR invalid; "
+ "aligning end to %d-byte boundary\n", res, align);
+ res->end = roundup(res->end, align) - 1;
+ }
+}
+
static acpi_status
setup_resource(struct acpi_resource *acpi_res, void *data)
{
@@ -107,6 +131,7 @@ setup_resource(struct acpi_resource *acpi_res, void *data)
res->start = start;
res->end = end;
res->child = NULL;
+ align_resource(info->bridge, res);
if (!(pci_probe & PCI_USE__CRS)) {
dev_printk(KERN_DEBUG, &info->bridge->dev,
--
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