REGRESSION with pcim_intx()

[Damien Le Moal <dlemoal@kernel.org>]

Commit 25216afc9db5 ("PCI: Add managed pcim_intx()") is causing a regression,
which is easy to see using qemu with an AHCI device and the ahci driver
compiled as a module.

1) Boot qemu: the AHCI controller is initialized and the drive(s) attached to
it visible.
2) Run "rmmod ahci": the drives go away, all normal
3) Re-initialize the AHCI adapter and rescan the drives by running "modprobe
ahci". That fails with the message "pci 0000:00:1f.2: Resources present before
probing"

The reason is that before commit 25216afc9db5, pci_intx(dev, 0) was called to
disable INTX as MSI are used for the adapter, and for that case, pci_intx()
would NOT allocate a device resource if the INTX enable/disable state was not
being changed:

	if (new != pci_command) {
		struct pci_devres *dr;

		pci_write_config_word(pdev, PCI_COMMAND, new);

		dr = find_pci_dr(pdev);
		if (dr && !dr->restore_intx) {
			dr->restore_intx = 1;
			dr->orig_intx = !enable;
		}
	}

The former code was only looking for the resource and not allocating it.

Now, with pcim_intx() being used, the intx resource is *always* allocated,
including when INTX is disabled when the device is being disabled on rmmod.
This leads to the device resource list to always have the intx resource
remaining and thus causes the modprobe error.

Reverting Commit 25216afc9db5 is one solution to fix this, and I can send a
patch for that, unless someone has an idea how to fix this ? I tried but I do
not see a clean way of fixing this...
Thoughts ?

-- 
Damien Le Moal
Western Digital Research