PCI Updates For The Linux 4.10 Kernel

The PCI subsystem updates for the Linux 4.10 merge window were sent in a few days ago.

One of the big changes to the Linux kernel's PCI code this time around is support for PCI on ARM64/AArch64 boxes with ACPI. There was theoretical support before, but now there is finally 64-bit ARM hardware using ACPI and PCI, to which some quirks were needed for enabling the actual hardware.

The PCI code in Linux 4.10 also now includes runtime power management support for hotplug ports and runtime suspend for Intel UHCI that uses platform-specific wake-up signaling. There is also a fix to avoid unnecessary link retrains for ASPM (Active State Power Management, what still sends chills to the minds of some power users from the ASPM regression a few years back).

With the PCI changes this cycle also comes the addition of exposing the device revision of a PCI device to user-space via sysfs. This was done by Collabora's Emil Velikov as the DRM library would like to be able to see a graphics card's revision in this efficient way rather than the former method that involved having to wake/power-up the graphics card to query it. Aside from libdrm, libpciaccess is another potential user of this new sysfs entry.

Some new hardware enablement this cycle includes NVIDIA Tegra210 support (Tegra X1), Layerscape LS1046a, and Qualcomm MSM8996 (Snapdragon 820) PCI support.

A list of all the PCI changes can be found via this pull request.