PCI: Handle read-only BARs on AMD CS553x devices

Some AMD CS553x devices have read-only BARs because of a firmware or
hardware defect.  There's a workaround in quirk_cs5536_vsa(), but it no
longer works after 36e8164882ca ("PCI: Restore detection of read-only
BARs").  Prior to 36e8164882ca, we filled in res->start; afterwards we
leave it zeroed out.  The quirk only updated the size, so the driver tried
to use a region starting at zero, which didn't work.

Expand quirk_cs5536_vsa() to read the base addresses from the BARs and
hard-code the sizes.

On Nix's system BAR 2's read-only value is 0x6200.  Prior to 36e8164882ca,
we interpret that as a 512-byte BAR based on the lowest-order bit set.  Per
datasheet sec 5.6.1, that BAR (MFGPT) requires only 64 bytes; use that to
avoid clearing any address bits if a platform uses only 64-byte alignment.

[bhelgaas: changelog, reduce BAR 2 size to 64]
Fixes: 36e8164882ca ("PCI: Restore detection of read-only BARs")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=85991#c4
Link: http://support.amd.com/TechDocs/31506_cs5535_databook.pdf
Link: http://support.amd.com/TechDocs/33238G_cs5536_db.pdf
Reported-and-tested-by: Nix <nix@esperi.org.uk>
Signed-off-by: Myron Stowe <myron.stowe@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: stable@vger.kernel.org	# v.2.6.27+

1 files changed, 37 insertions, 3 deletions

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index e52356aa09b8..903d5078b5ed 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -324,18 +324,52 @@ static void quirk_s3_64M(struct pci_dev *dev)
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_S3,      PCI_DEVICE_ID_S3_868,           quirk_s3_64M);
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_S3,      PCI_DEVICE_ID_S3_968,           quirk_s3_64M);
 
+static void quirk_io(struct pci_dev *dev, int pos, unsigned size,
+                     const char *name)
+{
+        u32 region;
+        struct pci_bus_region bus_region;
+        struct resource *res = dev->resource + pos;
+
+        pci_read_config_dword(dev, PCI_BASE_ADDRESS_0 + (pos << 2), &region);
+
+        if (!region)
+                return;
+
+        res->name = pci_name(dev);
+        res->flags = region & ~PCI_BASE_ADDRESS_IO_MASK;
+        res->flags |=
+                (IORESOURCE_IO | IORESOURCE_PCI_FIXED | IORESOURCE_SIZEALIGN);
+        region &= ~(size - 1);
+
+        /* Convert from PCI bus to resource space */
+        bus_region.start = region;
+        bus_region.end = region + size - 1;
+        pcibios_bus_to_resource(dev->bus, res, &bus_region);
+
+        dev_info(&dev->dev, FW_BUG "%s quirk: reg 0x%x: %pR\n",
+                 name, PCI_BASE_ADDRESS_0 + (pos << 2), res);
+}
+
 /*
  * Some CS5536 BIOSes (for example, the Soekris NET5501 board w/ comBIOS
  * ver. 1.33  20070103) don't set the correct ISA PCI region header info.
  * BAR0 should be 8 bytes; instead, it may be set to something like 8k
  * (which conflicts w/ BAR1's memory range).
+ *
+ * CS553x's ISA PCI BARs may also be read-only (ref:
+ * https://bugzilla.kernel.org/show_bug.cgi?id=85991 - Comment #4 forward).
  */
 static void quirk_cs5536_vsa(struct pci_dev *dev)
 {
+        static char *name = "CS5536 ISA bridge";
+
         if (pci_resource_len(dev, 0) != 8) {
-                struct resource *res = &dev->resource[0];
-                res->end = res->start + 8 - 1;
-                dev_info(&dev->dev, "CS5536 ISA bridge bug detected (incorrect header); workaround applied\n");
+                quirk_io(dev, 0,   8, name);    /* SMB */
+                quirk_io(dev, 1, 256, name);    /* GPIO */
+                quirk_io(dev, 2,  64, name);    /* MFGPT */
+                dev_info(&dev->dev, "%s bug detected (incorrect header); workaround applied\n",
+                         name);
         }
 }
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_CS5536_ISA, quirk_cs5536_vsa);