From d2f54d9b3ee32bc006a7ff25d716b32feba4b522 Mon Sep 17 00:00:00 2001 From: Bjorn Helgaas Date: Wed, 27 Nov 2013 15:31:07 -0700 Subject: [PATCH] PCI: Prevent bus conflicts while checking for bridge apertures pci_bridge_check_ranges() determines whether the bridge supports an I/O aperture and a prefetchable memory aperture. Previously, if the I/O aperture was unsupported, disabled, or configured at [io 0x0000-0x0fff], we wrote 0xf0 to PCI_IO_BASE and PCI_IO_LIMIT, which, if the bridge supports it, enables the I/O aperture at [io 0xf000-0xffff]. The enabled aperture may conflict with other devices in the system. Similarly, we wrote 0xfff0 to PCI_PREF_MEMORY_BASE and PCI_PREF_MEMORY_LIMIT, which enables the prefetchable memory aperture at [mem 0xfff00000-0xffffffff], and that may also conflict with other devices. All we need to know is whether the base and limit registers are writable, so we can use values that leave the apertures disabled, e.g., PCI_IO_BASE = 0xf0, PCI_IO_LIMIT = 0xe0, PCI_PREF_MEMORY_BASE = 0xfff0, PCI_PREF_MEMORY_LIMIT = 0xffe0. Writing non-zero values to both the base and limit registers means we detect whether either or both are writable, as we did before. Reported-by: Jason Gunthorpe Based-on-patch-by: Jason Gunthorpe Signed-off-by: Bjorn Helgaas --- drivers/pci/setup-bus.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c index 219a4106480..80350299a6e 100644 --- a/drivers/pci/setup-bus.c +++ b/drivers/pci/setup-bus.c @@ -665,21 +665,23 @@ static void pci_bridge_check_ranges(struct pci_bus *bus) pci_read_config_word(bridge, PCI_IO_BASE, &io); if (!io) { - pci_write_config_word(bridge, PCI_IO_BASE, 0xf0f0); + 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) b_res[0].flags |= IORESOURCE_IO; + /* DECchip 21050 pass 2 errata: the bridge may miss an address disconnect boundary by one PCI data phase. Workaround: do not use prefetching on this device. */ if (bridge->vendor == PCI_VENDOR_ID_DEC && bridge->device == 0x0001) return; + pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem); if (!pmem) { pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE, - 0xfff0fff0); + 0xffe0fff0); pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem); pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE, 0x0); } -- 2.43.2