When the operating system is booted with the default ASPM policy (POLICY_DEFAULT), current code is querying the enable/disable states from ASPM registers to determine the policy. For example, a BIOS could set the power saving state to performance and clear all ASPM control registers. A balanced ASPM policy could enable L0s and disable L1. A power conscious BIOS could enable both L0s and L1 to trade off latency and performance vs. power. After hotplug removal, pcie_aspm_exit_link_state() function clears the ASPM registers. An insertion following hotplug removal reads incorrect policy as ASPM disabled even though ASPM was enabled during boot. This is caused by the fact that same function is used for reconfiguring ASPM regardless of the power on state. ------------------------ Changes from v5 (https://www.spinics.net/lists/arm-kernel/msg571758.html) ------------------------ - rebase to 4.11-rc3 - Split pci_aspm_init() body into pci_aspm_init_upstream() and pci_aspm_init_downstream() for bridge and endpoint specific code behavior. - Get rid of function0 function. Detect downstream link in pci_aspm_init_upstream() instead Sinan Kaya (5): PCI/ASPM: introduce pci_aspm_init() and add to pci_init_capabilities() PCI/ASPM: split pci_aspm_init() into two PCI/ASPM: add init hook to device_add PCI/ASPM: save power on values during bridge init PCI/ASPM: move link_state cleanup to bridge remove drivers/pci/pcie/aspm.c | 137 ++++++++++++++++++++++++++++++++---------------- drivers/pci/probe.c | 3 ++ drivers/pci/remove.c | 3 +- include/linux/pci.h | 2 + 4 files changed, 98 insertions(+), 47 deletions(-) -- 1.9.1
