PCI: qcom: Program T_POWER_ON

Some platforms have incorrect T_POWER_ON value programmed in hardware.
Generally these will be corrected by bootloaders, but not all targets
support bootloaders to program correct values. That means the
LTR_L1.2_THRESHOLD value calculated by aspm.c can be wrong, which can
result in improper L1.2 exit behavior. If AER happens to be supported and
enabled, the error may be *reported* via AER.

Parse the 't-power-on-us' property from each Root Port node and program it
as part of host initialization using dw_pcie_program_t_power_on() before
link training.

This property in added to the dtschema here [1].

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
[mani: reworded comment]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link[1]: https://lore.kernel.org/all/20260205093346.667898-1-krishna.chundru@oss.qualcomm.com/
Link: https://patch.msgid.link/20260428-t_power_on_fux-v5-3-f1ef926a91ff@oss.qualcomm.com

1 files changed, 14 insertions, 0 deletions

diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index 9173369cca87..65688e28f10d 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -276,6 +276,7 @@ struct qcom_pcie_perst {
 struct qcom_pcie_port {
 	struct list_head list;
 	struct phy *phy;
+	u32 l1ss_t_power_on;
 	struct list_head perst;
 };
 
@@ -1349,6 +1350,14 @@ static int qcom_pcie_phy_power_on(struct qcom_pcie *pcie)
 	return 0;
 }
 
+static void qcom_pcie_configure_ports(struct qcom_pcie *pcie)
+{
+	struct qcom_pcie_port *port;
+
+	list_for_each_entry(port, &pcie->ports, list)
+		dw_pcie_program_t_power_on(pcie->pci, port->l1ss_t_power_on);
+}
+
 static int qcom_pcie_host_init(struct dw_pcie_rp *pp)
 {
 	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
@@ -1387,6 +1396,8 @@ static int qcom_pcie_host_init(struct dw_pcie_rp *pp)
 	dw_pcie_remove_capability(pcie->pci, PCI_CAP_ID_MSIX);
 	dw_pcie_remove_ext_capability(pcie->pci, PCI_EXT_CAP_ID_DPC);
 
+	qcom_pcie_configure_ports(pcie);
+
 	qcom_pcie_perst_deassert(pcie);
 
 	if (pcie->cfg->ops->config_sid) {
@@ -1868,6 +1879,9 @@ static int qcom_pcie_parse_port(struct qcom_pcie *pcie, struct device_node *node
 	if (ret)
 		return ret;
 
+	/* TODO: Move to DWC core after multi Root Port support is added */
+	of_property_read_u32(node, "t-power-on-us", &port->l1ss_t_power_on);
+
 	port->phy = phy;
 	INIT_LIST_HEAD(&port->list);
 	list_add_tail(&port->list, &pcie->ports);