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

On 9/21/26 1:34 PM, Manivannan Sadhasivam wrote:

On Mon, Sep 21, 2026 at 04:40:43PM +0530, Krishna Chaitanya Chundru wrote:

quoted

On 9/21/2026 2:09 PM, Konrad Dybcio wrote:

quoted

On 9/11/26 8:50 AM, Krishna Chaitanya Chundru wrote:

quoted

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.

Can you specify what issue can be seen without this series? I'd assume the
link will fail to enter L1.2 and will result in slightly more power drain as
the link can only enter L1.1.

Would that produce an explicit warning message somewhere?

i.e. can I reasonably be able to tell I'm missing this change and
I need it?

(if not, this is of course not a blocker, but the answer to that
question is always worth sharing)

Konrad