[PATCH] gx1fb: (try to) play nicer with various BIOSes

Seems that the CS5530A chip used in Geode GX1 systems has some crazy feature
that causes SMI traps when accessing the PCI configuration space of the video
device.  Various GX1 BIOSes seem to use this 'feature' to hide the real BARs
of the device.  This patch disables these traps (in an early PCI fixup) so
that Linux sees the real, physical BARs and not the virtual ones provided by
the BIOS.

This should allow the GX1 framebuffer driver to work on more systems that have
different BIOSes as the driver no longer guesses at what the virtual BARs
mean.

I'm not entirely sure it the correct solution as I can neither test regular
VGA console nor the X's 'cyrix' video driver so there might be some breakage
there -- probably best to get some more testers before applying it.

Signed-off-by: Antonino Daplas <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/arch/i386/pci/fixup.c b/arch/i386/pci/fixup.c
index 65f67070db64..83c3645ccc43 100644
--- a/arch/i386/pci/fixup.c
+++ b/arch/i386/pci/fixup.c
@@ -449,3 +449,19 @@ static void __devinit pci_post_fixup_toshiba_ohci1394(struct pci_dev *dev)
 }
 DECLARE_PCI_FIXUP_ENABLE(PCI_VENDOR_ID_TI, 0x8032,
                          pci_post_fixup_toshiba_ohci1394);
+
+
+/*
+ * Prevent the BIOS trapping accesses to the Cyrix CS5530A video device
+ * configuration space.
+ */
+static void __devinit pci_early_fixup_cyrix_5530(struct pci_dev *dev)
+{
+        u8 r;
+        /* clear 'F4 Video Configuration Trap' bit */
+        pci_read_config_byte(dev, 0x42, &r);
+        r &= 0xfd;
+        pci_write_config_byte(dev, 0x42, r);
+}
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_CYRIX, PCI_DEVICE_ID_CYRIX_5530_LEGACY,
+                        pci_early_fixup_cyrix_5530);