[PATCH 2/3] PCI: dwc: Improve msg_atu_index error handling

[Niklas Cassel <cassel@kernel.org>]

Only try to dedicate an outbound iATU to MSG TLP if use_atu_msg is set.
If use_atu_msg is not set, it is completely useless to bump the index.

Additionally, if use_atu_msg is set, and there is no available outbound
iatu available, return an error.

Fixes: e1a4ec1a9520 ("PCI: dwc: Add generic MSG TLP support for sending PME_Turn_Off when system suspend")
Signed-off-by: Niklas Cassel <cassel@kernel.org>
---
 drivers/pci/controller/dwc/pcie-designware-host.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index cca5fc886409..991fe5b9a7b3 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -982,7 +982,14 @@ static int dw_pcie_iatu_setup(struct dw_pcie_rp *pp)
 		dev_warn(pci->dev, "Ranges exceed outbound iATU size (%d)\n",
 			 pci->num_ob_windows);
 
-	pp->msg_atu_index = ++i;
+	if (pp->use_atu_msg) {
+		if (pci->num_ob_windows > ++i) {
+			pp->msg_atu_index = i;
+		} else {
+			dev_err(pci->dev, "Cannot add outbound window for MSG TLP\n");
+			return -ENOMEM;
+		}
+	}
 
 	i = 0;
 	resource_list_for_each_entry(entry, &pp->bridge->dma_ranges) {
-- 
2.52.0