PCI: add PCI-X/PCI-Express read control interfaces

This patch introduces an interface to read and write PCI-X / PCI-Express 
maximum read byte count values from PCI config space. There is a second 
function that returns the maximum _designed_ read byte count, which marks the 
maximum value for a device, since some drivers try to set MMRBC to the 
highest allowed value and rely on such a function.

Based on patch set by Stephen Hemminger <shemminger@linux-foundation.org>

Cc: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: Peter Oruba <peter.oruba@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 16 insertions, 0 deletions

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index 01d8f8a8843c..75bd6a8648f6 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -627,6 +627,22 @@ DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_8131_BRIDGE, quirk_
 DECLARE_PCI_FIXUP_RESUME(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_8131_BRIDGE, quirk_amd_8131_ioapic);
 #endif /* CONFIG_X86_IO_APIC */
 
+/*
+ * Some settings of MMRBC can lead to data corruption so block changes.
+ * See AMD 8131 HyperTransport PCI-X Tunnel Revision Guide
+ */
+static void __init quirk_amd_8131_mmrbc(struct pci_dev *dev)
+{
+        unsigned char revid;
+
+        pci_read_config_byte(dev, PCI_REVISION_ID, &revid);
+        if (dev->subordinate && revid <= 0x12) {
+                printk(KERN_INFO "AMD8131 rev %x detected, disabling PCI-X MMRBC\n",
+                        revid);
+                dev->subordinate->bus_flags |= PCI_BUS_FLAGS_NO_MMRBC;
+        }
+}
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_8131_BRIDGE, quirk_amd_8131_mmrbc);
 
 /*
  * FIXME: it is questionable that quirk_via_acpi