On Wed, Jun 24, 2020 at 11:15 PM Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote: > > On Fri, Jun 12, 2020 at 01:48:19PM -0700, David E. Box wrote: > > StorageD3Enable is a boolean property that indicates that the platform > > wants to use D3 for PCIe storage drives during suspend-to-idle. It is a > > BIOS work around that is currently in use on shipping systems like some > > Intel Comet Lake platforms. It is meant to change default driver policy for > > suspend that may cause higher power consumption. > > > > Add the DSD property for recognition by fwnode calls and provide an > > exported symbol for device drivers to use to read the property as needed. > > > > Link: https://docs.microsoft.com/en-us/windows-hardware/design/component-guidelines/power-management-for-storage-hardware-devices-intro > > Signed-off-by: David E. Box <david.e.box@xxxxxxxxxxxxxxx> > > --- > > drivers/acpi/property.c | 3 +++ > > drivers/pci/pci-acpi.c | 59 +++++++++++++++++++++++++++++++++++++++++ > > include/linux/pci.h | 2 ++ > > 3 files changed, 64 insertions(+) > > > > diff --git a/drivers/acpi/property.c b/drivers/acpi/property.c > > index e601c4511a8b..c2e2ae774a19 100644 > > --- a/drivers/acpi/property.c > > +++ b/drivers/acpi/property.c > > @@ -45,6 +45,9 @@ static const guid_t prp_guids[] = { > > /* Thunderbolt GUID for WAKE_SUPPORTED: 6c501103-c189-4296-ba72-9bf5a26ebe5d */ > > GUID_INIT(0x6c501103, 0xc189, 0x4296, > > 0xba, 0x72, 0x9b, 0xf5, 0xa2, 0x6e, 0xbe, 0x5d), > > + /* Storage device needs D3 GUID: 5025030f-842f-4ab4-a561-99a5189762d0 */ > > + GUID_INIT(0x5025030f, 0x842f, 0x4ab4, > > + 0xa5, 0x61, 0x99, 0xa5, 0x18, 0x97, 0x62, 0xd0), > > }; > > > > /* ACPI _DSD data subnodes GUID: dbb8e3e6-5886-4ba6-8795-1319f52a966b */ > > diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c > > index d21969fba6ab..732df524e09c 100644 > > --- a/drivers/pci/pci-acpi.c > > +++ b/drivers/pci/pci-acpi.c > > @@ -972,6 +972,65 @@ static bool acpi_pci_bridge_d3(struct pci_dev *dev) > > return val == 1; > > } > > > > +/** > > + * pci_acpi_storage_d3 - whether root port requests D3 for idle suspend > > + * @pdev: PCI device to check > > + * > > + * Returns true if the ACPI companion device contains the "StorageD3Enable" > > + * _DSD property and the value is 1. This indicates that the root port is > > + * used by a storage device and the platform is requesting D3 for the > > + * device during suspend to idle in order to support platform pm. > > + */ > > +bool pci_acpi_storage_d3(struct pci_dev *dev) > > +{ > > + const struct fwnode_handle *fwnode; > > + struct acpi_device *adev; > > + struct pci_dev *root; > > + acpi_handle handle; > > + acpi_status status; > > + bool ret = false; > > + u8 val; > > + > > + /* > > + * Look for _DSD property specifying that the storage device on > > + * the port must use D3 to support deep platform power savings during > > + * suspend-to-idle > > + */ > > + root = pci_find_pcie_root_port(dev); > > I think this would need to be updated to apply to v5.8-rc1 after > 6ae72bfa656e ("PCI: Unify pcie_find_root_port() and > pci_find_pcie_root_port()"). > > https://git.kernel.org/linus/6ae72bfa656e > > > + if (!root) > > + return false; > > + > > + adev = ACPI_COMPANION(&root->dev); > > + if (!adev) { > > + /* > > + * It is possible that the ACPI companion is not yet bound > > + * for the root port so look it up manually here. > > + */ > > + if (!adev && !pci_dev_is_added(root)) > > + adev = acpi_pci_find_companion(&root->dev); > > I see that you copied this "ACPI companion not yet bound" thing from > acpi_pci_bridge_d3(). But it's ugly. > > Isn't there a way we can bind the ACPI companion during normal PCI > enumeration so we don't need this exception case? > > I really do not like the idea of putting this code in the PCI core > because AFAICT the PCI core can do nothing with this information. > > If we could make sure during enumeration that the root port always has > an ACPI companion, this code could go to the nvme driver itself. And > we could also clean up the ugliness in acpi_pci_bridge_d3(). > > Rafael, is that possible? I don't really know how the companion > device gets set. That's a bit convoluted. device_add() calls device_platform_notify(), before calling bus_add_device(). device_platform_notify() calls acpi_platform_notify() which invokes acpi_device_notify() that looks for the companion via type->find_companion() which for PCI points to acpi_pci_find_companion(). If found, the companion is attached to the dev structure as a physical_node, via acpi_bind_one(). So by the time bus_probe_device() runs, the companion should be there already - if it is there at all. The parent ACPI companion should be present when the child is probing too, as per the above. > Maybe this is could be done somewhere around pci_device_add()? It is done in there. It is not necessary to call acpi_pci_find_companion() from pci_acpi_storage_d3() as long as that function is required to be called by the target device's driver probe or later. Ths acpi_pci_bridge_d3() case is different, though, AFAICS, because it is invoked in the pci_pm_init() path, via pci_bridge_d3_possible(), and that gets called from pci_device_add() *before* calling device_add(). Mika, is that why acpi_pci_find_companion() gets callled from acpi_pci_bridge_d3()?
