PCI: Revert "PCI: Call pci_read_bridge_bases() from core instead of arch code"
Revert dff22d20 ("PCI: Call pci_read_bridge_bases() from core instead of arch code"). Reading PCI bridge windows is not arch-specific in itself, but there is PCI core code that doesn't work correctly if we read them too early. For example, Hannes found this case on an ARM Freescale i.mx6 board: pci_bus 0000:00: root bus resource [mem 0x01000000-0x01efffff] pci 0000:00:00.0: PCI bridge to [bus 01-ff] pci 0000:00:00.0: BAR 8: no space for [mem size 0x01000000] (mem window) pci 0000:01:00.0: BAR 2: failed to assign [mem size 0x00200000] pci 0000:01:00.0: BAR 1: failed to assign [mem size 0x00004000] pci 0000:01:00.0: BAR 0: failed to assign [mem size 0x00000100] The 00:00.0 mem window needs to be at least 3MB: the 01:00.0 device needs 0x204100 of space, and mem windows are megabyte-aligned. Bus sizing can increase a bridge window size, but never *decrease* it (see d65245c3 ("PCI: don't shrink bridge resources")). Prior to dff22d20, ARM didn't read bridge windows at all, so the "original size" was zero, and we assigned a 3MB window. After dff22d20, we read the bridge windows before sizing the bus. The firmware programmed a 16MB window (size 0x01000000) in 00:00.0, and since we never decrease the size, we kept 16MB even though we only needed 3MB. But 16MB doesn't fit in the host bridge aperture, so we failed to assign space for the window and the downstream devices. I think this is a defect in the PCI core: we shouldn't rely on the firmware to assign sensible windows. Ray reported a similar problem, also on ARM, with Broadcom iProc. Issues like this are too hard to fix right now, so revert dff22d20 . Reported-by: Hannes <email@example.com> Reported-by: Ray Jui <firstname.lastname@example.org> Link: http://lkml.kernel.org/r/CAAa04yFQEUJm7Jj1qMT57-LG7ZGtnhNDBe=PpSRa70Mj+XhW-A@mail.gmail.com Link: http://lkml.kernel.org/r/55F75BB8.email@example.com Signed-off-by: Bjorn Helgaas <firstname.lastname@example.org> Acked-by: Yinghai Lu <email@example.com> Acked-by: Lorenzo Pieralisi <firstname.lastname@example.org>