[RFC PATCH] PCI: designware: Skip allocating own MSI domain if using external MSI domain

[Shawn Lin <shawn.lin@rock-chips.com>]

On some platform, external MSI domain is using instead of the one
created by designware driver. For instance, if using GIC-V3-ITS
as a MSI domain, we only need set msi-map in the devicetree but
never need any bit in the designware driver to handle MSI stuff.
So skip allocating its own MSI domain for that case.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>

---

 drivers/pci/controller/dwc/pcie-designware-host.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index 29a0575..39254b1 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -278,6 +278,10 @@ int dw_pcie_allocate_domains(struct pcie_port *pp)
 		return -ENOMEM;
 	}
 
+	/* Rely on the external MSI domain */
+	if (device_property_read_bool(dev, "msi-map"))
+		return 0;
+
 	pp->msi_domain = pci_msi_create_irq_domain(fwnode,
 						   &dw_pcie_msi_domain_info,
 						   pp->irq_domain);
@@ -433,7 +437,8 @@ int dw_pcie_host_init(struct pcie_port *pp)
 	if (ret)
 		pci->num_viewport = 2;
 
-	if (IS_ENABLED(CONFIG_PCI_MSI)) {
+	if (IS_ENABLED(CONFIG_PCI_MSI) &&
+	    !device_property_read_bool(dev, "msi-map")) {
 		/*
 		 * If a specific SoC driver needs to change the
 		 * default number of vectors, it needs to implement
-- 
1.9.1