tree 80922aa70a57cf99fb94df909beacfe56e6f2c0e
parent b9e44fe5ecda4158c22bc1ea4bffa378a4f83f65
author Sarah Sharp <sarah.a.sharp@linux.intel.com> 1328656306 -0800
committer Sarah Sharp <sarah.a.sharp@linux.intel.com> 1329867908 -0800

USB: Fix handoff when BIOS disables host PCI device.

On some systems with an Intel Panther Point xHCI host controller, the
BIOS disables the xHCI PCI device during boot, and switches the xHCI
ports over to EHCI.  This allows the BIOS to access USB devices without
having xHCI support.

The downside is that the xHCI BIOS handoff mechanism will fail because
memory mapped I/O is not enabled for the disabled PCI device.
Jesse Barnes says this is expected behavior.  The PCI core will enable
BARs before quirks run, but it will leave it in an undefined state, and
it may not have memory mapped I/O enabled.

Make the generic USB quirk handler call pci_enable_device() to re-enable
MMIO, and call pci_disable_device() once the host-specific BIOS handoff
is finished.  This will balance the ref counts in the PCI core.  When
the PCI probe function is called, usb_hcd_pci_probe() will call
pci_enable_device() again.

This should be back ported to kernels as old as 2.6.31.  That was the
first kernel with xHCI support, and no one has complained about BIOS
handoffs failing due to memory mapped I/O being disabled on other hosts
(EHCI, UHCI, or OHCI).

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Acked-by: Oliver Neukum <oneukum@suse.de>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: stable@vger.kernel.org