On Sun, Jan 08, 2017 at 09:41:45AM +0100, Lukas Wunner wrote: > Currently PCIe ports are only allowed to go to D3 if the BIOS is dated > 2015 or newer 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 two EFI security updates in 2015 which encompass all machines > with Thunderbolt, but the achieved power saving should be made available > to users even if they haven't updated their BIOS. To this end, > 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 > the EFI update is installed. Users can pass pcie_port_pm=force on the > kernel command line if they cannot install the 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, the Thunderbolt > special case can be removed. > > Cc: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> Reviewed-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
