[+cc Rafael, linux-pm, since this is power management stuff https://lore.kernel.org/all/20220513110027.31015-1-manivannan.sadhasivam@xxxxxxxxxx/] On Fri, May 13, 2022 at 04:30:24PM +0530, Manivannan Sadhasivam wrote: > Hi, > > This series adds support for notifying the PCI drivers like NVMe about the > transition of PCI devices into powerdown mode during system suspend. > > Background > ---------- > > On Qcom SC7280 based Chrome platforms, the OS will turn off the power to all > PCIe devices during system suspend for aggressive powersaving. Currently, there > is no way for the PCI device drivers to learn about this situation. Some of the > drivers assume that the power will be retained and some others assume that the > power may be taken down. > > We faced the issue with NVMe PCI driver, where the driver expects the NVMe > device to be in APST (Autonomous Power State Transition) state for power saving > during system suspend. So when the power goes down, the NVMe driver fails to > bringup the device during resume. > > Previous work > ------------- > > We tried to fix this issue in a couple of ways: > > 1. The NVMe PCI driver checks for the existence of "StorageD3Enable" ACPI > property in the suspend path. If the property is found, the driver assumes that > the device may go to poweroff state and shutdowns the device accordingly. > > As like the ACPI based systems, we also tried to get the support in place for > DT based systems. But that didn't get accepted: > https://lore.kernel.org/all/Yl+6V3pWuyRYuVV8@xxxxxxxxxxxxx/T/ > > 2. Keith Busch proposed a module params based approach. The parameter when set, > will allow the driver to support APST during suspend. Absence of that parameter > will let the driver shutdown the device. > > This also did not get accepted: > https://lore.kernel.org/linux-nvme/20220201165006.3074615-1-kbusch@xxxxxxxxxx/ > > Proposal > -------- > > Christoph suggested to add a notification in the PCI/PM core to let the NVMe > driver know that the device will go into powerdown state during suspend. > https://lore.kernel.org/all/Yg0wklcJ3ed76Jbk@xxxxxxxxxxxxx/ > > Hence in this series, a "suspend_poweroff" flag is introduced in the host bridge > struct. When this flag is set by the PCI RC drivers, the PCI device driver like > NVMe can shutdown the device during suspend. > > In the coming days, the usage of this flag could be extended to other PCI > drivers as well. > > Testing > ------- > > This series has been tested on SC7280 IDP board connected to a NVMe PCI device. > > Thanks, > Mani > > Manivannan Sadhasivam (3): > PCI: Add a flag to notify PCI drivers about powerdown during suspend > PCI: dwc: qcom: Set suspend_poweroff flag for SC7280 > nvme-pci: Make use of "suspend_poweroff" flag during system suspend > > drivers/nvme/host/pci.c | 3 ++- > drivers/pci/controller/dwc/pcie-qcom.c | 6 ++++++ > include/linux/pci.h | 1 + > 3 files changed, 9 insertions(+), 1 deletion(-) > > -- > 2.25.1 >
