On Tue, May 17, 2022 at 08:39:08PM +0530, Manivannan Sadhasivam wrote: > On Mon, May 16, 2022 at 03:18:17PM -0500, Bjorn Helgaas wrote: > > On Fri, May 13, 2022 at 04:30:25PM +0530, Manivannan Sadhasivam wrote: > > > On some systems like Chromebooks based on Qcom chipsets, the OS may > > > powerdown all PCIe devices during system suspend for aggressive > > > powersaving. In that case, the PCI host controller drivers need to notify > > > the PCI device drivers that the power will be taken off during system > > > suspend so that the drivers can prepare the devices accordingly. > > > > "The OS may powerdown all PCIe devices ..." makes it sound like this > > is an OS policy decision. Where exactly (what function) is that? > > > > Or if it's not an OS policy decision, but rather some property of the > > hardware, say that specifically. > > On SC7280, it is the Resource Power Manager(RPMh) that's powering > the devices down by cutting off the PCIe voltage domain. But the > SC7280 RC driver itself may put the PCIe devices into D3cold state > during system suspend. > https://lore.kernel.org/lkml/CAE-0n53ho2DX2rqQMvvKAuDCfsWW62TceTaNPzv5Mn_NQ-U6dA@xxxxxxxxxxxxxx/T/ > > So to cover both cases (one is a hardware independent of SoC and > another one is the device driver), and to be generic, I've used the > term "OS" after looking at the previous flags. This sort of device-specific behavior definitely needs a pointer to an example. Otherwise it seems like it could be generic PCIe behavior that should be documented in the PCIe base spec. > > > One prime example is the PCI NVMe driver. This flag can be used by the > > > driver to shutdown the NVMe device during suspend and recover it during > > > resume. Apparently nvme is broken, or at least sub-optimal, without this flag. What other drivers will be similarly affected? > > > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx> > > > --- > > > include/linux/pci.h | 1 + > > > 1 file changed, 1 insertion(+) > > > > > > diff --git a/include/linux/pci.h b/include/linux/pci.h > > > index 60adf42460ab..069caf1fe88d 100644 > > > --- a/include/linux/pci.h > > > +++ b/include/linux/pci.h > > > @@ -578,6 +578,7 @@ struct pci_host_bridge { > > > unsigned int preserve_config:1; /* Preserve FW resource setup */ > > > unsigned int size_windows:1; /* Enable root bus sizing */ > > > unsigned int msi_domain:1; /* Bridge wants MSI domain */ > > > + unsigned int suspend_poweroff:1; /* OS may poweroff devices during system suspend */ > > > > > > /* Resource alignment requirements */ > > > resource_size_t (*align_resource)(struct pci_dev *dev,
