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    PCI: add PCI Express ASPM support · 7d715a6c
    Shaohua Li 提交于
    PCI Express ASPM defines a protocol for PCI Express components in the D0
    state to reduce Link power by placing their Links into a low power state
    and instructing the other end of the Link to do likewise. This
    capability allows hardware-autonomous, dynamic Link power reduction
    beyond what is achievable by software-only controlled power management.
    However, The device should be configured by software appropriately.
    Enabling ASPM will save power, but will introduce device latency.
    
    This patch adds ASPM support in Linux. It introduces a global policy for
    ASPM, a sysfs file /sys/module/pcie_aspm/parameters/policy can control
    it. The interface can be used as a boot option too. Currently we have
    below setting:
            -default, BIOS default setting
            -powersave, highest power saving mode, enable all available ASPM
    state and clock power management
            -performance, highest performance, disable ASPM and clock power
    management
    By default, the 'default' policy is used currently.
    
    In my test, power difference between powersave mode and performance mode
    is about 1.3w in a system with 3 PCIE links.
    
    Note: some devices might not work well with aspm, either because chipset
    issue or device issue. The patch provide API (pci_disable_link_state),
    driver can disable ASPM for specific device.
    Signed-off-by: NShaohua Li <shaohua.li@intel.com>
    Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>
    7d715a6c
pci-sysfs.c 17.9 KB