[PATCH 2/5] PCI: dwc: Add support for retaining link during host init

[Krishna Chaitanya Chundru]

Some platforms keep the PCIe link up across bootloader and kernel
handoff. In such cases, reinitializing the root complex is unnecessary
if the DWC glue drivers wants to retain the PCIe link.

Introduce a link_retain flag in struct dw_pcie_rp to indicate that
the link should be preserved. When this flag is set by DWC glue drivers,
skip dw_pcie_setup_rc() and only initialize MSI, avoiding redundant
configuration steps.

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru at oss.qualcomm.com>
---
 drivers/pci/controller/dwc/pcie-designware-host.c | 11 ++++++++---
 drivers/pci/controller/dwc/pcie-designware.h      |  1 +
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index 372207c33a857b4c98572bb1e9b61fa0080bc871..d050df3f22e9507749a8f2fedd4c24fca43fb410 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -655,9 +655,14 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)
 	if (ret)
 		goto err_free_msi;
 
-	ret = dw_pcie_setup_rc(pp);
-	if (ret)
-		goto err_remove_edma;
+	if (!pp->link_retain) {
+		ret = dw_pcie_setup_rc(pp);
+		if (ret)
+			goto err_remove_edma;
+	} else {
+		dw_pcie_msi_init(pp);
+	}
+
 
 	if (!dw_pcie_link_up(pci)) {
 		ret = dw_pcie_start_link(pci);
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index 31685951a080456b8834aab2bf79a36c78f46639..8acab751b66a06e8322e027ab55dc0ecfdcf634c 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -439,6 +439,7 @@ struct dw_pcie_rp {
 	struct pci_config_window *cfg;
 	bool			ecam_enabled;
 	bool			native_ecam;
+	bool			link_retain;
 };
 
 struct dw_pcie_ep_ops {

-- 
2.34.1