On Fri, Apr 01, 2022 at 01:44:42PM +0200, Rafael J. Wysocki wrote: > On Fri, Apr 1, 2022 at 5:40 AM Mario Limonciello > <mario.limonciello@xxxxxxx> wrote: > > > > acpi_pci_bridge_d3(dev) returns "true" if "dev" is a hotplug bridge > > that can handle hotplug events while in D3. Previously this meant: > > > > 1) "dev" has a _PS0 or _PR0 method, or > > > > 2) The Root Port above "dev" has a _DSD with a "HotPlugSupportInD3" > > property with value 1. > > > > This did not consider_S0W, which tells us the deepest D-state from > > which a device can wake itself (ACPI v6.4, sec 7.3.20). > > > > On some platforms, e.g., AMD Yellow Carp, firmware may supply > > "HotPlugSupportInD3" even though the platform does not supply power > > resources through _PRW and _S0W tells us the device cannot wake from > > More importantly, it doesn't supply a wakeup GPE number through _PRW, > so from the ACPI perspective the bridge has no way of generating > wakeup signals. Perfect, thanks. That's the missing piece about _PRW. > > D3hot. With the previous code, these devices could be put in D3hot > > and hotplugged devices would not be recognized without manually > > rescanning. > > > > If _S0W exists and says the Root Port cannot wake itself from D3hot, > > return "false" to indicate that "dev" cannot handle hotplug events > > while in D3. > > > > 1) "dev" has a _PS0 or _PR0 method, or > > > > 2a) The Root Port above "dev" has _PRW and > > > > 2b) If the Root Port above "dev" has _S0W, it can wake from D3hot or > > D3cold and > > > > 2c) The Root Port above "dev" has a _DSD with a > > "HotPlugSupportInD3" property with value 1. > > > > Windows 10 and Windows 11 both will prevent the bridge from going in D3 > > when the firmware is configured this way and this change aligns the > > handling of the situation to be the same. > > > > Link: https://uefi.org/htmlspecs/ACPI_Spec_6_4_html/07_Power_and_Performance_Mgmt/device-power-management-objects.html?highlight=s0w#s0w-s0-device-wake-state > > Link: https://docs.microsoft.com/en-us/windows-hardware/drivers/pci/dsd-for-pcie-root-ports#identifying-pcie-root-ports-supporting-hot-plug-in-d3 > > Fixes: 26ad34d510a87 ("PCI / ACPI: Whitelist D3 for more PCIe hotplug ports") > > Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx> > > -- > > v5->v6: > > * Re-order checks to only check for _DSD if necessary as suggested by Bjorn. > > * Adjust commit message wording > > * Drop rewording comment patch, just apply it while moving text to avoid > > ping-ponging the same lines in the commits. > > v4-v5: > > * Don't fail if _S0W is missing > > --- > > drivers/pci/pci-acpi.c | 25 +++++++++++++++++++------ > > 1 file changed, 19 insertions(+), 6 deletions(-) > > > > diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c > > index 1f15ab7eabf8..5ab797e2709d 100644 > > --- a/drivers/pci/pci-acpi.c > > +++ b/drivers/pci/pci-acpi.c > > @@ -976,7 +976,9 @@ bool acpi_pci_bridge_d3(struct pci_dev *dev) > > { > > const union acpi_object *obj; > > struct acpi_device *adev; > > + unsigned long long state; > > struct pci_dev *rpdev; > > + acpi_status status; > > > > if (acpi_pci_disabled || !dev->is_hotplug_bridge) > > return false; > > @@ -985,12 +987,6 @@ bool acpi_pci_bridge_d3(struct pci_dev *dev) > > if (acpi_pci_power_manageable(dev)) > > return true; > > > > - /* > > - * The ACPI firmware will provide the device-specific properties through > > - * _DSD configuration object. Look for the 'HotPlugSupportInD3' property > > - * for the root port and if it is set we know the hierarchy behind it > > - * supports D3 just fine. > > - */ > > rpdev = pcie_find_root_port(dev); > > if (!rpdev) > > return false; > > @@ -999,6 +995,23 @@ bool acpi_pci_bridge_d3(struct pci_dev *dev) > > if (!adev) > > return false; > > > > + /* > > + * If the bridge can't wake from D3hot, it can't signal hotplug > > + * events in D3hot. > > I would say "If the bridge cannot signal wakeup signals at all, it > cannot signal hotplug events from low-power states including D3hot and > D3cold." > > With the two above remarks addressed, please feel free to add > > Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> Great, thanks! > > + */ > > + if (!adev->wakeup.flags.valid) > > + return false; > > + > > + status = acpi_evaluate_integer(adev->handle, "_S0W", NULL, &state); > > + if (ACPI_SUCCESS(status) && state < ACPI_STATE_D3_HOT) > > + return false; > > + > > + /* > > + * The ACPI firmware will provide the device-specific properties through > > + * _DSD configuration object. Look for the 'HotPlugSupportInD3' property > > + * for the root port and if it is set we make an assumption that the > > + * hierarchy behind it supports D3 as well. > > + */ > > if (acpi_dev_get_property(adev, "HotPlugSupportInD3", > > ACPI_TYPE_INTEGER, &obj) < 0) > > return false; > > -- > > 2.34.1 > >
