Re: [PATCH v2 0/4] PCI: Introduce pci_suspend_retains_context() API

[Bjorn Helgaas <helgaas@kernel.org>]

On Tue, May 19, 2026 at 01:41:19PM +0530, Manivannan Sadhasivam via B4 Relay wrote:
> Hi all,
> 
> This series introduces a new PCI API, pci_suspend_retains_context() 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 PCIe RC
> 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@oss.qualcomm.com>
> ---
> Changes in v2:
> - Renamed the API to pci_suspend_retains_context()
> - Reworded the commit messages to include L10_REFCLK_ON + T_COMMONMODE as the
>   L1ss exit latency
> - Rebased on top of v7.1-rc1
> 
> ---
> 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_suspend_retains_context() API during suspend
> 
>  drivers/nvme/host/pci.c                |  3 ++-
>  drivers/pci/controller/dwc/pcie-qcom.c | 12 ++++++++++++
>  drivers/pci/pci.c                      | 34 ++++++++++++++++++++++++++++++++++
>  include/linux/pci.h                    |  9 +++++++++
>  4 files changed, 57 insertions(+), 1 deletion(-)

Applied to pci/pm for v7.2, thanks, Mani!