path: root/Documentation
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authorMika Westerberg <>2016-06-02 11:17:12 +0300
committerBjorn Helgaas <>2016-06-13 14:57:36 -0500
commit9d26d3a8f1b0c442339a235f9508bdad8af91043 (patch)
treefda7bf01c07d954d9dceb2a0f1c7a9beba74a67e /Documentation
parent43f7f88b9362e1f26603b45932069bbd6e15a1e1 (diff)
PCI: Put PCIe ports into D3 during suspend
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 unnecessarily and may 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. Tested-by: Lukas Wunner <> Signed-off-by: Mika Westerberg <> Signed-off-by: Bjorn Helgaas <> Acked-by: Rafael J. Wysocki <>
Diffstat (limited to 'Documentation')
1 files changed, 4 insertions, 0 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 82b42c958d1c..86edee4cedd4 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3047,6 +3047,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
ports driver.
+ pcie_port_pm= [PCIE] PCIe port power management handling:
+ off Disable power management of all PCIe ports
+ force Forcibly enable power management of all PCIe ports
pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
nomsi Do not use MSI for native PCIe PME signaling (this makes
all PCIe root ports use INTx for all services).