On Friday, April 29, 2016 11:51:57 AM Mika Westerberg wrote: > Currently the Linux PCI core does not touch power state of PCI bridges and > PCIe ports when system suspend is entered. Leaving them in D0 consumes > power which is not good thing in portable devices such as laptops. This may > also prevent the CPU from entering deeper C-states. > > With recent PCIe hardware we can power down the ports to save power given > that we take into account few restrictions: > > - The PCIe port hardware is recent enough, starting from 2015. > > - Devices connected to PCIe ports are effectively in D3cold once the port > is transitioned to D3 (the config space is not accessible anymore and > the link may be powered down). > > - Devices behind the PCIe port need to be allowed to transition to D3cold > and back. There is a way both drivers and userspace can forbid this. > > - If the device behind the PCIe port is capable of waking the system it > needs to be able to do so from D3cold. > > This patch adds a new flag to struct pci_device called 'bridge_d3'. This > flag is set and cleared by the PCI core whenever there is a change in power > management state of any of the devices behind the PCIe port. When system > later on is suspended we only need to check this flag and if it is true > transition the port to D3 otherwise we leave it in D0. > > Also provide override mechanism via command line parameter > "pcie_port_pm=[off|force]" that can be used to disable or enable the > feature regardless of the BIOS manufacturing date. > > Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> -- 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
