Re: [PATCH v3 3/3] PCI: qcom: Program T_POWER_ON

[Shawn Lin]

在 2026/03/30 星期一 16:16, Krishna Chaitanya Chundru 写道:
> On 3/13/2026 8:19 AM, Shawn Lin wrote:
> > 在 2026/03/11 星期三 20:40, Krishna Chaitanya Chundru 写道:
> > > 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 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;
> >
> > u16?
> >
> > >       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);
> >
> > Ditto?
> the property has -us and doesn't have $ref to indicate if it is u32 or 
> u16, by default it is u32 property only.
> can we can't keep it as u16 even if have always less than u16.

It came from dw_pcie_program_t_power_on(u16 t_power_on) which
take u16, so the value will be truncated anyway. Well, it's up to you,
just a bypass comment. :)

> - Krishna Chaitanya.
> > > +
> > >       port->phy = phy;
> > >       INIT_LIST_HEAD(&port->list);
> > >       list_add_tail(&port->list, &pcie->ports);