Re: [PATCH v3 3/3] PCI: qcom: Program T_POWER_ON
From: Krishna Chaitanya Chundru
Date: Mon Mar 16 2026 - 01:06:17 EST
On 3/16/2026 10:23 AM, Manivannan Sadhasivam wrote:
On Wed, Mar 11, 2026 at 06:10:40PM +0530, Krishna Chaitanya Chundru wrote:As this per root port, we can summit changes to merge first so that we can move this to
Some platforms have incorrect T_POWER_ON value programmed in hardware.Since this is going to be common for all controller drivers, it'd be good to
Generally these will be corrected by bootloaders, but not all targets
support bootloaders to program correct values due to that
LTR_L1.2_THRESHOLD value calculated by aspm driver can be wrong, which
can result in improper L1.2 exit behavior and if AER happens to be
supported and enabled, the error may be *reported* via AER.
Parse "t-power-on-us" property from each root port node and program them
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@xxxxxxxxxxxxxxxx>
Link[1]: https://lore.kernel.org/all/20260205093346.667898-1-krishna.chundru@xxxxxxxxxxxxxxxx/
---
drivers/pci/controller/dwc/pcie-qcom.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index 67a16af69ddc75fca1b123e70715e692a91a9135..63d5628e988d3c07f42099c0d86e6b80fd54ce32 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -269,6 +269,7 @@ struct qcom_pcie_perst {
struct qcom_pcie_port {
struct list_head list;
struct phy *phy;
+ u32 l1ss_t_power_on;
struct list_head perst;
};
@@ -1283,6 +1284,14 @@ 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);
@@ -1317,6 +1326,8 @@ 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) {
@@ -1759,6 +1770,8 @@ static int qcom_pcie_parse_port(struct qcom_pcie *pcie, struct device_node *node
if (ret)
return ret;
+ of_property_read_u32(node, "t-power-on-us", &port->l1ss_t_power_on);
+
move this inside the dwc API.
dwc.
- Krishna Chaitanya.
- Mani