| Message ID | 20221031223356.32570-1-mario.limonciello@amd.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v5] PCI/ACPI: PCI/ACPI: Validate devices with power resources support D3 | expand |
On Mon, Oct 31, 2022 at 05:33:55PM -0500, Mario Limonciello wrote: > Firmware typically advertises that ACPI devices that represent PCIe > devices can support D3 by a combination of the value returned by > _S0W as well as the HotPlugSupportInD3 _DSD [1]. > > `acpi_pci_bridge_d3` looks for this combination but also contains > an assumption that if an ACPI device contains power resources the PCIe > device it's associated with can support D3. This was introduced > from commit c6e331312ebf ("PCI/ACPI: Whitelist hotplug ports for > D3 if power managed by ACPI"). > > Some firmware configurations for "AMD Pink Sardine" do not support > wake from D3 in _S0W for the ACPI device representing the PCIe root > port used for tunneling. The PCIe device will still be opted into > runtime PM in the kernel [2] because of the logic within > `acpi_pci_bridge_d3`. This currently happens because the ACPI > device contains power resources. > > When the thunderbolt driver is loaded two device links are created: > * USB4 router <- PCIe root port for tunneling > * USB4 router <- XHCI PCIe device > > These device links are created because the ACPI devices declare the > `usb4-host-interface` _DSD [3]. For both links the USB4 router is the > supplier and these other devices are the consumers. > Here is a demonstration of this topology that occurs: > > | > ├─ 00:03.1 > | | "PCIe root port used for tunneling" > | | ACPI Path: \_SB_.PCI0.GP11 > | | ACPI Power Resources: Yes I guess this means it has _PR0 and/or _PS0? (same for devices below) > | | ACPI _S0W return value: 0 > | | Device Links: supplier:pci:0000:c4:00.5 > | └─ PCIe Power state: D0 What bus does 00:03.1 lead to? I guess it doesn't lead to any of the devices below? > └─ 00:08.3 > | ACPI Path: \_SB_.PCI0.GP19 > ├─ PCIe Power state: D0 I guess 00:08.3 is a Root Port leading to bus c4? > ├─ c4:00.3 > | | "XHCI PCIe device used for tunneling" > | | ACPI Path: \_SB_.PCI0.GP19.XHC3 > | | ACPI Power Resources: Yes > | | ACPI _S0W return value: 4 > | | Device Links: supplier:pci:0000:c4:00.5 > | └─ PCIe Power state: D3cold > └─ c4:00.5 > | "USB4 Router" > | ACPI Path: \_SB_.PCI0.GP19.NHI0 > | ACPI Power Resources: Yes > | ACPI _S0W return value: 4 > | Device Links: consumer:pci:0000:00:03.1 consumer:pci:0000:c4:00.3 > └─ PCIe Power state: D3cold I'm reading the excellent Documentation/driver-api/device_link.rst and trying to match up with this topology. This is a case where 00:03.1 is a consumer of c4:00.5. The driver core automatically enforces that children are suspended before parents, but since 00:03.1 is an aunt (not a child) of c4:00.5, the device link enforces the requirement that 00:03.1 be suspended before c4:00.5. Right? Is c4:00.5 an NHI? The PCI power states shown above are the failure case? c4:00.5 *should* remain in D0 as long as 00:03.1 is in D0, but was instead put in D3cold? > Currently runtime PM is allowed for all of these devices. This is because they all have _PR0 and/or _PS0? (Diagram doesn't show that for 00:08.3, but I assume it must?) And I guess they all must have dev->is_hotplug_bridge set? > This means that > when all consumers are idle long enough, they will runtime suspend to > enter their deepest allowed sleep state. Once all consumers are in their > deepest allowed sleep state the suppliers will enter the deepest sleep > state as well. > > * The PCIe root port for tunneling doesn't support waking from D3hot or > D3cold so although runtime suspended it stays in D0. > * The XHCI PCIe device supports wakeup from D3cold so it runtime suspends > to D3cold. > * Both consumers are in their deepest state and the USB4 router supports > wakeup from D3cold, so it runtime suspends into this state. > > At least for AMD's case the hardware designer's expectation is the USB4 > router should have also remained in D0 since the PCIe root port for > tunneling remained in D0 and a device link exists between the two devices. > The current Linux behavior is undefined. Is the requirement that the supplier can never be in a lower-power state than the consumer? I guess that's *not* actually a requirement even though that's the effect of this patch in this situation. If it *were* that simple, we would just check the supplier and consumer power states instead of looking at all these ACPI properties. > Instead of making the assertion that the device can support D3 (and thus > runtime PM) solely from the presence of ACPI power resources, move the check > to later on in the function, which will have validated that the ACPI device > supports wake from D3hot or D3cold. > > This fix prevents the USB4 router being put into D3 when the firmware > says that ACPI device representing the PCIe root port for tunneling can't > handle it while still allowing ACPI devices that don't have the > HotplugSupportInD3 _DSD to also enter D3 if they have power resources that > can wake from D3. So I guess this changes what acpi_pci_bridge_d3() returns for 00:03.1? Previously it returned "true" because it has _PR0/_PS0 (so acpi_pci_power_manageable() is true), but now it will return "false" because _S0W says it can only wake from D0? > Link: https://learn.microsoft.com/en-us/windows-hardware/drivers/pci/dsd-for-pcie-root-ports#identifying-pcie-root-ports-supporting-hot-plug-in-d3 [1] > Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pci/pcie/portdrv_pci.c?id=v6.0#n126 [2] > Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/thunderbolt/acpi.c?id=v6.0#n29 [3] > Fixes: dff6139015dc6 ("PCI/ACPI: Allow D3 only if Root Port can signal and wake from D3") > Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com> > Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > Signed-off-by: Mario Limonciello <mario.limonciello@amd.com> > --- > v4->v5: > * Update github->git.kernel.org > * Correct arrow direction > * Clarify some commit message comments from Lukas' feedback. > v3->v4: > * Pick up tags > * Add more details to the commit message > v2->v3: > * Reword commit message > v1->v2: > * Just return value of acpi_pci_power_manageable (Rafael) > * Remove extra word in commit message > --- > drivers/pci/pci-acpi.c | 7 ++----- > 1 file changed, 2 insertions(+), 5 deletions(-) > > diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c > index a46fec776ad77..8c6aec50dd471 100644 > --- a/drivers/pci/pci-acpi.c > +++ b/drivers/pci/pci-acpi.c > @@ -984,10 +984,6 @@ bool acpi_pci_bridge_d3(struct pci_dev *dev) > if (acpi_pci_disabled || !dev->is_hotplug_bridge) > return false; > > - /* Assume D3 support if the bridge is power-manageable by ACPI. */ > - if (acpi_pci_power_manageable(dev)) > - return true; > - > rpdev = pcie_find_root_port(dev); > if (!rpdev) > return false; > @@ -1023,7 +1019,8 @@ bool acpi_pci_bridge_d3(struct pci_dev *dev) > obj->integer.value == 1) > return true; > > - return false; > + /* Assume D3 support if the bridge is power-manageable by ACPI. */ > + return acpi_pci_power_manageable(dev); > } > > int acpi_pci_set_power_state(struct pci_dev *dev, pci_power_t state) > -- > 2.34.1 >
diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c index a46fec776ad77..8c6aec50dd471 100644 --- a/drivers/pci/pci-acpi.c +++ b/drivers/pci/pci-acpi.c @@ -984,10 +984,6 @@ bool acpi_pci_bridge_d3(struct pci_dev *dev) if (acpi_pci_disabled || !dev->is_hotplug_bridge) return false; - /* Assume D3 support if the bridge is power-manageable by ACPI. */ - if (acpi_pci_power_manageable(dev)) - return true; - rpdev = pcie_find_root_port(dev); if (!rpdev) return false; @@ -1023,7 +1019,8 @@ bool acpi_pci_bridge_d3(struct pci_dev *dev) obj->integer.value == 1) return true; - return false; + /* Assume D3 support if the bridge is power-manageable by ACPI. */ + return acpi_pci_power_manageable(dev); } int acpi_pci_set_power_state(struct pci_dev *dev, pci_power_t state)
Firmware typically advertises that ACPI devices that represent PCIe devices can support D3 by a combination of the value returned by _S0W as well as the HotPlugSupportInD3 _DSD [1]. `acpi_pci_bridge_d3` looks for this combination but also contains an assumption that if an ACPI device contains power resources the PCIe device it's associated with can support D3. This was introduced from commit c6e331312ebf ("PCI/ACPI: Whitelist hotplug ports for D3 if power managed by ACPI"). Some firmware configurations for "AMD Pink Sardine" do not support wake from D3 in _S0W for the ACPI device representing the PCIe root port used for tunneling. The PCIe device will still be opted into runtime PM in the kernel [2] because of the logic within `acpi_pci_bridge_d3`. This currently happens because the ACPI device contains power resources. When the thunderbolt driver is loaded two device links are created: * USB4 router <- PCIe root port for tunneling * USB4 router <- XHCI PCIe device These device links are created because the ACPI devices declare the `usb4-host-interface` _DSD [3]. For both links the USB4 router is the supplier and these other devices are the consumers. Here is a demonstration of this topology that occurs: | ├─ 00:03.1 | | "PCIe root port used for tunneling" | | ACPI Path: \_SB_.PCI0.GP11 | | ACPI Power Resources: Yes | | ACPI _S0W return value: 0 | | Device Links: supplier:pci:0000:c4:00.5 | └─ PCIe Power state: D0 └─ 00:08.3 | ACPI Path: \_SB_.PCI0.GP19 ├─ PCIe Power state: D0 ├─ c4:00.3 | | "XHCI PCIe device used for tunneling" | | ACPI Path: \_SB_.PCI0.GP19.XHC3 | | ACPI Power Resources: Yes | | ACPI _S0W return value: 4 | | Device Links: supplier:pci:0000:c4:00.5 | └─ PCIe Power state: D3cold └─ c4:00.5 | "USB4 Router" | ACPI Path: \_SB_.PCI0.GP19.NHI0 | ACPI Power Resources: Yes | ACPI _S0W return value: 4 | Device Links: consumer:pci:0000:00:03.1 consumer:pci:0000:c4:00.3 └─ PCIe Power state: D3cold Currently runtime PM is allowed for all of these devices. This means that when all consumers are idle long enough, they will runtime suspend to enter their deepest allowed sleep state. Once all consumers are in their deepest allowed sleep state the suppliers will enter the deepest sleep state as well. * The PCIe root port for tunneling doesn't support waking from D3hot or D3cold so although runtime suspended it stays in D0. * The XHCI PCIe device supports wakeup from D3cold so it runtime suspends to D3cold. * Both consumers are in their deepest state and the USB4 router supports wakeup from D3cold, so it runtime suspends into this state. At least for AMD's case the hardware designer's expectation is the USB4 router should have also remained in D0 since the PCIe root port for tunneling remained in D0 and a device link exists between the two devices. The current Linux behavior is undefined. Instead of making the assertion that the device can support D3 (and thus runtime PM) solely from the presence of ACPI power resources, move the check to later on in the function, which will have validated that the ACPI device supports wake from D3hot or D3cold. This fix prevents the USB4 router being put into D3 when the firmware says that ACPI device representing the PCIe root port for tunneling can't handle it while still allowing ACPI devices that don't have the HotplugSupportInD3 _DSD to also enter D3 if they have power resources that can wake from D3. Link: https://learn.microsoft.com/en-us/windows-hardware/drivers/pci/dsd-for-pcie-root-ports#identifying-pcie-root-ports-supporting-hot-plug-in-d3 [1] Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pci/pcie/portdrv_pci.c?id=v6.0#n126 [2] Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/thunderbolt/acpi.c?id=v6.0#n29 [3] Fixes: dff6139015dc6 ("PCI/ACPI: Allow D3 only if Root Port can signal and wake from D3") Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com> --- v4->v5: * Update github->git.kernel.org * Correct arrow direction * Clarify some commit message comments from Lukas' feedback. v3->v4: * Pick up tags * Add more details to the commit message v2->v3: * Reword commit message v1->v2: * Just return value of acpi_pci_power_manageable (Rafael) * Remove extra word in commit message --- drivers/pci/pci-acpi.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-)