ASPM: Fix pcie devices with non-pcie children

Since 3.2.12 and 3.3, some systems are failing to boot with a BUG_ON.
Some other systems using the pata_jmicron driver fail to boot because no
disks are detected.  Passing pcie_aspm=force on the kernel command line
works around it.

The cause: commit 4949be16822e ("PCI: ignore pre-1.1 ASPM quirking when
ASPM is disabled") changed the behaviour of pcie_aspm_sanity_check() to
always return 0 if aspm is disabled, in order to avoid cases where we
changed ASPM state on pre-PCIe 1.1 devices.

This skipped the secondary function of pcie_aspm_sanity_check which was
to avoid us enabling ASPM on devices that had non-PCIe children, causing
trouble later on.  Move the aspm_disabled check so we continue to honour
that scenario.

Addresses https://bugzilla.kernel.org/show_bug.cgi?id=42979 and
          http://bugs.debian.org/665420

Reported-by: Romain Francoise <romain@orebokech.com> # kernel panic
Reported-by: Chris Holland <bandidoirlandes@gmail.com> # disk detection trouble
Signed-off-by: Matthew Garrett <mjg@redhat.com>
Cc: stable@vger.kernel.org
Tested-by: Hatem Masmoudi <hatem.masmoudi@gmail.com> # Dell Latitude E5520
Tested-by: janek <jan0x6c@gmail.com> # pata_jmicron with JMB362/JMB363
[jn: with more symptoms in log message]
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/pci/pcie/aspm.c

@@ -508,9 +508,6 @@ static int pcie_aspm_sanity_check(struct pci_dev *pdev)
 	int pos;
 	u32 reg32;
 
-	if (aspm_disabled)
-		return 0;
-
 	/*
 	 * Some functions in a slot might not all be PCIe functions,
 	 * very strange. Disable ASPM for the whole slot
@@ -519,6 +516,16 @@ static int pcie_aspm_sanity_check(struct pci_dev *pdev)
 		pos = pci_pcie_cap(child);
 		if (!pos)
 			return -EINVAL;
+
+		/*
+		 * If ASPM is disabled then we're not going to change
+		 * the BIOS state. It's safe to continue even if it's a
+		 * pre-1.1 device
+		 */
+
+		if (aspm_disabled)
+			continue;
+
 		/*
 		 * Disable ASPM for pre-1.1 PCIe device, we follow MS to use
 		 * RBER bit to determine if a function is 1.1 version device