• John W. Linville's avatar
    [PATCH] PCI: restore BAR values after D3hot->D0 for devices that need it · fec59a71
    John W. Linville authored
    Some PCI devices (e.g. 3c905B, 3c556B) lose all configuration
    (including BARs) when transitioning from D3hot->D0.  This leaves such
    a device in an inaccessible state.  The patch below causes the BARs
    to be restored when enabling such a device, so that its driver will
    be able to access it.
    
    The patch also adds pci_restore_bars as a new global symbol, and adds a
    correpsonding EXPORT_SYMBOL_GPL for that.
    
    Some firmware (e.g. Thinkpad T21) leaves devices in D3hot after a
    (re)boot.  Most drivers call pci_enable_device very early, so devices
    left in D3hot that lose configuration during the D3hot->D0 transition
    will be inaccessible to their drivers.
    
    Drivers could be modified to account for this, but it would
    be difficult to know which drivers need modification.  This is
    especially true since often many devices are covered by the same
    driver.  It likely would be necessary to replicate code across dozens
    of drivers.
    
    The patch below should trigger only when transitioning from D3hot->D0
    (or at boot), and only for devices that have the "no soft reset" bit
    cleared in the PM control register.  I believe it is safe to include
    this patch as part of the PCI infrastructure.
    
    The cleanest implementation of pci_restore_bars was to call
    pci_update_resource.  Unfortunately, that does not currently exist
    for the sparc64 architecture.  The patch below includes a null
    implemenation of pci_update_resource for sparc64.
    
    Some have expressed interest in making general use of the the
    pci_restore_bars function, so that has been exported to GPL licensed
    modules.
    Signed-off-by: default avatarJohn W. Linville <linville@tuxdriver.com>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
    fec59a71
pci.h 45.9 KB