3 files changed, 25 insertions, 0 deletions

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index f4adba2d1dd3..12625d90f8b5 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -163,9 +163,16 @@ int __pci_read_base(struct pci_dev *dev, enum pci_bar_type type,
                         struct resource *res, unsigned int pos)
 {
         u32 l, sz, mask;
+        u16 orig_cmd;
 
         mask = type ? PCI_ROM_ADDRESS_MASK : ~0;
 
+        if (!dev->mmio_always_on) {
+                pci_read_config_word(dev, PCI_COMMAND, &orig_cmd);
+                pci_write_config_word(dev, PCI_COMMAND,
+                        orig_cmd & ~(PCI_COMMAND_MEMORY | PCI_COMMAND_IO));
+        }
+
         res->name = pci_name(dev);
 
         pci_read_config_dword(dev, pos, &l);
@@ -173,6 +180,9 @@ int __pci_read_base(struct pci_dev *dev, enum pci_bar_type type,
         pci_read_config_dword(dev, pos, &sz);
         pci_write_config_dword(dev, pos, l);
 
+        if (!dev->mmio_always_on)
+                pci_write_config_word(dev, PCI_COMMAND, orig_cmd);
+
         /*
          * All bits set in sz means the device isn't working properly.
          * If the BAR isn't implemented, all bits must be 0.  If it's a
diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index 3a81d9d44019..202efa6f57c4 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -91,6 +91,19 @@ static void __devinit quirk_resource_alignment(struct pci_dev *dev)
 }
 DECLARE_PCI_FIXUP_HEADER(PCI_ANY_ID, PCI_ANY_ID, quirk_resource_alignment);
 
+/*
+ * Decoding should be disabled for a PCI device during BAR sizing to avoid
+ * conflict. But doing so may cause problems on host bridge and perhaps other
+ * key system devices. For devices that need to have mmio decoding always-on,
+ * we need to set the dev->mmio_always_on bit.
+ */
+static void __devinit quirk_mmio_always_on(struct pci_dev *dev)
+{
+        if ((dev->class >> 8) == PCI_CLASS_BRIDGE_HOST)
+                dev->mmio_always_on = 1;
+}
+DECLARE_PCI_FIXUP_EARLY(PCI_ANY_ID, PCI_ANY_ID, quirk_mmio_always_on);
+
 /* The Mellanox Tavor device gives false positive parity errors
  * Mark this device with a broken_parity_status, to allow
  * PCI scanning code to "skip" this now blacklisted device.
diff --git a/include/linux/pci.h b/include/linux/pci.h
index f26fda76b87f..b1d17956a153 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -270,6 +270,8 @@ struct pci_dev {
         unsigned int    d1_support:1;   /* Low power state D1 is supported */
         unsigned int    d2_support:1;   /* Low power state D2 is supported */
         unsigned int    no_d1d2:1;      /* Only allow D0 and D3 */
+        unsigned int    mmio_always_on:1;       /* disallow turning off io/mem
+                                                   decoding during bar sizing */
         unsigned int    wakeup_prepared:1;
         unsigned int    d3_delay;       /* D3->D0 transition time in ms */