PCI/MSI: Let pci_msi_get_domain use struct device::msi_domain

Now that we can easily find which MSI domain a PCI device is
using, use dev_get_msi_domain as a way to retrieve the information.

The original code is still used as a fallback.
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Hanjun Guo <hanjun.guo@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: <linux-arm-kernel@lists.infradead.org>
Cc: Yijing Wang <wangyijing@huawei.com>
Cc: Ma Jun <majun258@huawei.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Duc Dang <dhdang@apm.com>
Cc: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Jason Cooper <jason@lakedaemon.net>
Link: http://lkml.kernel.org/r/1438091186-10244-8-git-send-email-marc.zyngier@arm.comSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

drivers/pci/msi.c

@@ -39,14 +39,16 @@ struct irq_domain * __weak arch_get_pci_msi_domain(struct pci_dev *dev)
 
 static struct irq_domain *pci_msi_get_domain(struct pci_dev *dev)
 {
-	struct irq_domain *domain = NULL;
+	struct irq_domain *domain;
 
-	if (dev->bus->msi)
-		domain = dev->bus->msi->domain;
-	if (!domain)
-		domain = arch_get_pci_msi_domain(dev);
+	domain = dev_get_msi_domain(&dev->dev);
+	if (domain)
+		return domain;
 
+	if (dev->bus->msi && (domain = dev->bus->msi->domain))
 		return domain;
+
+	return arch_get_pci_msi_domain(dev);
 }
 
 static int pci_msi_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)