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

[Shawn Lin <shawn.lin@rock-chips.com>]

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@oss.qualcomm.com>
>>> Link[1]: 
>>> https://lore.kernel.org/all/20260205093346.667898-1-krishna.chundru@oss.qualcomm.com/ 
>>>
>>> ---
>>>   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);
>>>
> 
>