• Ivan Kokshaysky's avatar
    [PATCH] PCI: pci_enable_device vs bridges bugs · a5a278a6
    Ivan Kokshaysky authored
    Bug #1 (found by Jay Estabrook).
    On Alpha, under certain circumstances the firmware may close the IO
    window of PCI-to-PCI bridge even if there is IO behind.
    This wouldn't be a problem - linux PCI setup code does set up this
    window properly, but in addition the firmware clears the IO-enable
    bit in the PCI_COMMAND register of the bridge.
    Since we don't call pci_enable_* routines for bridges in non-hotplug
    path, we end up with disabled IO. Fixed by adding pci_enable_bridges()
    to pci_assign_unassigned_resources().
    Architectures which don't use the latter, but do use other setup-bus
    code (parisc?) also should call pci_enable_bridges() for each root bus.
    
    Bug #2 (closely related to #1).
    As it turns out, pci_enable_device() doesn't work for bridges at all,
    only for regular devices (header type 0) due to 0x3f mask passed to
    pci_enable_device_bars(). The mask should be (1 << PCI_NUM_RESOURCES) - 1.
    
    Bug #3 (quite a few archs, including i386).
    pcibios_enable_device() does only check first 6 resources (regardless
    of the mask) to decide whether or not to enable IO and MEM.
    Bridge resources start at 7.
    
    #2 and #3 affect hotplug. I wonder, has anybody ever tried *bridged*
    PCI card behind a hot-plug controller?
    a5a278a6
pci.c 20 KB