[PATCH 0/4] PCI: Introduce pci_dev_suspend_retention_supported() API

[Manivannan Sadhasivam via B4 Relay]

Hi all,

This series introduces a new PCI API pci_dev_suspend_retention_supported() to
let the client drivers know whether they can expect context retention across
suspend/resume or not and uses it in the NVMe PCI host driver.

This new API is targeted to abstract the PCI power management details away from
the client drivers. This is needed because client drivers like NVMe make use of
APIs such as pm_suspend_via_firmware() and decide to keep the device in low
power mode if this API returns 'false'. But some platforms may have other
limitations like in the case of Qcom, where if the RC driver removes the
resource vote to allow the SoC to enter low power mode, it cannot reliably exit
the L1ss state when the endpoint asserts CLKREQ#. So in this case also, the
client drivers cannot keep the device in low power state during suspend and
expect context retention.

And these limitations may just keep adding in the future. Without a unified
API, the client drivers have to implement their own logic which may cause code
duplication and may also lead to drivers missing some of the platform
limitations.

Once this series gets merged, we can extend this API usage to other client
drivers as well.

Testing
=======

This series is tested on Qualcomm Hamoa based Lenovo Thinkpad T14s latop with
NVMe drive.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxxxxxxxx>
---
Manivannan Sadhasivam (4):
      PCI: Introduce an API to check if RC/platform can retain device context during suspend
      PCI: Indicate context lost if L1ss exit is broken during resume from system suspend
      PCI: qcom: Indicate broken L1ss exit during resume from system suspend
      nvme-pci: Use pci_dev_suspend_retention_supported() API during suspend

 drivers/nvme/host/pci.c                |  3 ++-
 drivers/pci/controller/dwc/pcie-qcom.c | 11 +++++++++++
 drivers/pci/pci.c                      | 34 ++++++++++++++++++++++++++++++++++
 include/linux/pci.h                    |  9 +++++++++
 4 files changed, 56 insertions(+), 1 deletion(-)
---
base-commit: 591cd656a1bf5ea94a222af5ef2ee76df029c1d2
change-id: 20260414-l1ss-fix-6c9cf2451944

Best regards,
--  
Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxxxxxxxx>