PCIe ports are only allowed to go to D3 if the BIOS is dated 2015+ to avoid potential issues with old chipsets. However for Thunderbolt we know that even the oldest controller, Light Ridge (2010), is able to suspend its ports to D3 just fine. We're about to add runtime PM for Thunderbolt on the Mac. Apple has released multiple EFI updates since 2015 but not everyone has installed them (https://support.apple.com/en-us/HT201222). Those users should still benefit from the achievable power saving. Thus, special-case Thunderbolt in pci_bridge_d3_possible(). This allows the Thunderbolt controller to power down but the root port to which the Thunderbolt controller is attached remains in D0 unless an EFI update is installed. Users can pass pcie_port_pm=force on the kernel command line if they cannot install an EFI update but still want to benefit from the additional power saving of putting the root port into D3. In practice, root ports can be suspended to D3 without issues at least on 2012 Ivy Bridge machines. If the BIOS cut-off date is ever lowered to 2010 and runtime PM is allowed on all native hotplug ports, the Thunderbolt special case can be removed. Cc: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> Cc: Andreas Noever <andreas.noever@xxxxxxxxx> Cc: Tomas Winkler <tomas.winkler@xxxxxxxxx> Cc: Amir Levy <amir.jer.levy@xxxxxxxxx> Reviewed-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx> --- drivers/pci/pci.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 7904d02ffdb9..441083a0d5b0 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -2224,7 +2224,7 @@ void pci_config_pm_runtime_put(struct pci_dev *pdev) * @bridge: Bridge to check * * This function checks if it is possible to move the bridge to D3. - * Currently we only allow D3 for recent enough PCIe ports. + * Currently we only allow D3 for recent enough PCIe ports and Thunderbolt. */ bool pci_bridge_d3_possible(struct pci_dev *bridge) { @@ -2253,6 +2253,10 @@ bool pci_bridge_d3_possible(struct pci_dev *bridge) if (pci_bridge_d3_force) return true; + /* Even the oldest 2010 Thunderbolt controller supports D3. */ + if (bridge->is_thunderbolt) + return true; + /* * It should be safe to put PCIe ports from 2015 or newer * to D3. -- 2.11.0
