Re: [PATCH v5 0/3] PCI: qcom: Program T_POWER_ON value for L1.2 exit timing

[Manivannan Sadhasivam]

On Tue, Apr 28, 2026 at 02:07:14PM +0530, Krishna Chaitanya Chundru wrote:
> The T_POWER_ON indicates the time (in μs) that a Port requires the port
> on the opposite side of Link to wait in L1.2.Exit after sampling CLKREQ#
> asserted before actively driving the interface. This value is used by
> the ASPM driver to compute the LTR_L1.2_THRESHOLD.
> 
> Currently, qcom root port exposes T_POWER_ON value of zero in the L1SS
> capability registers, leading to incorrect LTR_L1.2_THRESHOLD calculations,
> which can result in improper L1.2 exit behavior and can trigger AER's.
> 
> In this series, qcom controller drivers read the devicetree property
> "t-power-on" which got merged recently[1], and use that value to over
> write default/wrong value.
> 
> To convert T_POWER_ON in to T_POWER_ON_SCALE & T_POWER_ON_VALUE created
> a pcie_encode_t_power_on() helper in aspm.c and also created
> dw_pcie_program_t_power_on() helper for other drivers to use these
> helpers.
> 
> Link [1]: https://lore.kernel.org/all/20260205093346.667898-1-krishna.chundru@xxxxxxxxxxxxxxxx/
> 
> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@xxxxxxxxxxxxxxxx>

Series LGTM!

@Bjorn: Could you please ack patch 1 if you are OK with it?

- Mani

> ---
> Changes in v5:
> - Initialize *scale & *value to zero incase of ASPM is disabled pointed
>   by sashiko.
> - Use dwc readl & writel API's instead of direct readl & writel pointed
>   by sashiko
> - couple of nits (Mani).
> - Link to v4: https://lore.kernel.org/r/20260404-t_power_on_fux-v4-0-2891391177f4@xxxxxxxxxxxxxxxx
> 
> Changes in v4:
> - calculate maxv from PCI_L1SS_CTL2_T_PWR_ON_VALUE to PCI_L1SS_CAP_P_PWR_ON_VALUE (Mani).
> - added a todo to move the reading the devicetree from qcom driver to
>   dwc once multi root port parsing support is added (Mani).
> - Link to v3: https://lore.kernel.org/r/20260311-t_power_on_fux-v3-0-9b1f1d09c6f3@xxxxxxxxxxxxxxxx
> 
> Changes in v3:
> - move pcie_encode_t_power_on() include/linux/pci.h to
>   drivers/pci/pci.h (Bjorn).
> - couple of changes in commit text and variable name like t_power_on (Bjorn).
> - remove return 0 from qcom_pcie_configure_ports (Bjorn).
> - used FIELD_MODIFY instead of FIELD_PREP (Bjorn).
> - Link to v2: https://lore.kernel.org/r/20260223-t_power_on_fux-v2-0-20c921262709@xxxxxxxxxxxxxxxx
> 
> Changes in v2:
> - Instead of hard coding the values in the driver, created a devicetree
>   property "t-power-on" to program it (Bjorn & Mani).
> - Link to v1: https://lore.kernel.org/r/20251104-t_power_on_fux-v1-1-eb5916e47fd7@xxxxxxxxxxxxxxxx
> 
> To: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> To: Jingoo Han <jingoohan1@xxxxxxxxx>
> To: Manivannan Sadhasivam <mani@xxxxxxxxxx>
> To: Lorenzo Pieralisi <lpieralisi@xxxxxxxxxx>
> To: Krzysztof Wilczyński <kwilczynski@xxxxxxxxxx>
> To: Rob Herring <robh@xxxxxxxxxx>
> Cc: linux-pci@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: linux-arm-msm@xxxxxxxxxxxxxxx
> 
> ---
> Krishna Chaitanya Chundru (3):
>       PCI/ASPM: Add helper to encode L1SS T_POWER_ON fields
>       PCI: dwc: Add helper to Program T_POWER_ON
>       PCI: qcom: Program T_POWER_ON
> 
>  drivers/pci/controller/dwc/pcie-designware.c | 28 +++++++++++++++++++
>  drivers/pci/controller/dwc/pcie-designware.h |  1 +
>  drivers/pci/controller/dwc/pcie-qcom.c       | 14 ++++++++++
>  drivers/pci/pci.h                            |  6 +++++
>  drivers/pci/pcie/aspm.c                      | 40 ++++++++++++++++++++++++++++
>  5 files changed, 89 insertions(+)
> ---
> base-commit: 3b3bea6d4b9c162f9e555905d96b8c1da67ecd5b
> change-id: 20251104-t_power_on_fux-70dc68377941
> 
> Best regards,
> --  
> Krishna Chaitanya Chundru <krishna.chundru@xxxxxxxxxxxxxxxx>
> 

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