Introduce weak arch_find_msi_chip() to find the match msi_chip.
Currently, MSI chip associates pci bus to msi_chip. Because in
ARM platform, there may be more than one MSI controller in system.
Associate pci bus to msi_chip help pci device to find the match
msi_chip and setup MSI/MSI-X irq correctly. But in other platform,
like in x86. we only need one MSI chip, because all device use
the same MSI address/data and irq etc. So it's no need to associate
pci bus to MSI chip, just use a arch function, arch_find_msi_chip()
to return the MSI chip for simplicity. The default weak
arch_find_msi_chip() used in ARM platform, find the MSI chip
by pci bus.

Signed-off-by: Yijing Wang <redacted>
---
 drivers/pci/msi.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index a77e7f7..539c11d 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c

@@ -29,9 +29,14 @@ static int pci_msi_enable = 1;
 
 /* Arch hooks */
 
+struct msi_chip * __weak arch_find_msi_chip(struct pci_dev *dev)
+{
+	return dev->bus->msi;
+}
+
 int __weak arch_setup_msi_irq(struct pci_dev *dev, struct msi_desc *desc)
 {
-	struct msi_chip *chip = dev->bus->msi;
+	struct msi_chip *chip = arch_find_msi_chip(dev);
 	int err;
 
 	if (!chip || !chip->setup_irq)

-- 
1.7.1