On Wed, 2009-01-14 at 11:48 -0800, Andrew Klossner wrote:
> When I moved from 2.6.27 to 2.6.28, one of my devices didn't work
> until I devised the attached patch. The kernel disallowed PCI I/O
> space resources behind the pseudo-bridge in the Freescale MPC8545
> because that bridge's config-space registers incorrectly report that
> it doesn't forward I/O space transactions.
>
> Checking for a specific vendor ID is hacky, but it got my system going
> again with only a few perturbed lines. Is there a more correct way to
> achieve this?
A few things yes.
First, can't you just set the PCI_COMMAND_IO bit from a quirk or at init
time rather than adding to code to cope with it being cleared later on ?
Also, the fact that it's detected as uninitialized shouldn't have broken
access to your device. If there is need for some IO space, for example
because a device requests some, the kernel should have re-opened that
window of the bridge.
Thus if that failed, it would be useful to track it down a bit more. You
can try enabling DEBUG in pci-common.c and pci-64.c, boot with "debug"
on the kernel command line and and send the resulting dmesg log
Ben.
> diff --git a/arch/powerpc/kernel/pci-common.c
> b/arch/powerpc/kernel/pci-common.c
> index f36936d..f9f0048 100644
> --- a/arch/powerpc/kernel/pci-common.c
> +++ b/arch/powerpc/kernel/pci-common.c
> @@ -985,6 +985,7 @@ static int __devinit
> pcibios_uninitialized_bridge_resource(struct pci_bus *bus,
> struct pci_dev *dev = bus->self;
> resource_size_t offset;
> u16 command;
> + u16 vendor;
> int i;
>
> /* We don't do anything if PCI_PROBE_ONLY is set */
> @@ -1030,7 +1031,16 @@ static int __devinit
> pcibios_uninitialized_bridge_resource(struct pci_bus *bus,
> * starting at low addresses -is- valid. What we do instead if
> that
> * we consider as unassigned anything that doesn't have IO
> enabled
> * in the PCI command register, and that's it.
> + * However, we don't do that if the bridge is internal to a
> Freescale
> + * CPU, as such bridges break the rules by, for example, not
> populating
> + * the PCI_COMMAND_IO bit.
> */
> + pci_read_config_word(dev, PCI_VENDOR_ID, &vendor);
> + if (vendor == PCI_VENDOR_ID_MOTOROLA ||
> + vendor == PCI_VENDOR_ID_FREESCALE) {
> + return 0;
> + }
> +
> pci_read_config_word(dev, PCI_COMMAND, &command);
> if (command & PCI_COMMAND_IO)
> return 0;
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