Re: [PATCH 0/8] arm64: dts: qcom: Add t-power-on-us property for PCIe root ports

[Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>]

On 9/21/2026 2:09 PM, Konrad Dybcio wrote:
> On 9/11/26 8:50 AM, Krishna Chaitanya Chundru wrote:
>> The Qualcomm PCIe host controller driver added support for parsing the
>> -power-on-us property[1] from each Root Port node and programming it as
>> art of host initialization (PCI: qcom: Program T_POWER_ON) [2]. Prior to
>> this, T_POWER_ON was expected to be programmed correctly in hardware or
>> by the bootloader, but not all targets support this, which can lead to an
>> incorrectly calculated LTR_L1.2_THRESHOLD in aspm.c and improper L1.2 exit
>> behavior.
> This is a good problem description. Does it have observable effects
> that could also be mentioned here, beyond perhaps lspci reporting
> an odd value?
we haven't seen direct problem till now, but we might seen some issue due to
incorrect LTR_L1.2_THRESHOLD value.
>> This series adds the t-power-on-us = <80>; property to the PCIe root
>> port node(s) on the following targets, so the controller programs the
>> correct T_POWER_ON value instead of relying on the (currently incorrect)
>> hardware default:
>>
>> - kodiak
>> - lemans
>> - monaco
>> - hamoa
>> - glymur
>> - talos
>> - sm8750
>> - kaanapali
> Because you said "currently incorrect", it clearly applies to all of
> these platforms. Are other ones that we support in the tree also
> affected?
yes all targets  will be affected, not sure about ipq platforms.
I added mostly active targets which we are currently using, I can extend if
recommended.

- Krishna Chaitanya.
>
> Konrad