[Bugfix] PCI, x86: Correctly allocate IRQs for PCI devices managed by non-PCI drivers

[Jiang Liu <jiang.liu@linux.intel.com>]

Commit 991de2e59090 ("PCI, x86: Implement pcibios_alloc_irq() and
pcibios_free_irq()") changes the way to allocate PCI legacy IRQ
for PCI devices on x86 platforms. Instead of allocating PCI legacy
IRQs when pcibios_enable_device() gets called, now pcibios_alloc_irq()
will be called by pci_device_probe() to allocate PCI legacy IRQs
when binding PCI drivers to PCI devices.

But some device drivers, such as eata, directly access PCI devices
without implementing corresponding PCI drivers, so pcibios_alloc_irq()
won't be called for those PCI devices and wrong IRQ number may be
used to manage the PCI device.

So detect such a case in pcibios_enable_device() by checking
pci_dev->driver is NULL and call pcibios_alloc_irq() to allocate PCI
legacy IRQs.

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
---
 arch/x86/pci/common.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/x86/pci/common.c b/arch/x86/pci/common.c
index 09d3afc0a181..60b237783582 100644
--- a/arch/x86/pci/common.c
+++ b/arch/x86/pci/common.c
@@ -685,6 +685,16 @@ void pcibios_free_irq(struct pci_dev *dev)
 
 int pcibios_enable_device(struct pci_dev *dev, int mask)
 {
+	/*
+	 * By design, pcibios_alloc_irq() will be called by pci_device_probe()
+	 * when binding a PCI device to a PCI driver. But some device drivers,
+	 * such as eata, directly make use of PCI devices without implementing
+	 * PCI device drivers, so pcibios_alloc_irq() won't be called for those
+	 * PCI devices.
+	 */
+	if (!dev->driver)
+		pcibios_alloc_irq(dev);
+
 	return pci_enable_resources(dev, mask);
 }
 
-- 
1.7.10.4