What would it take to enable PCIe on the mainline kernel? Is this a matter of changing/enabling some config settings or something a lot more involved? I have a Firefly RK3399 board that I'd like use with a Quectel EC25 LTE modem mini-PCIe module. As far as I could gather, mainline kernel already supports the modem via the QMI WWAN driver, but when I try the prebuilt mainline kernel from this thread, I can't even see the modem in lsusb output. The modem shows up in lsusb on 4.4 kernel just fine (although apparently one needs to build the QMI module separately to make it usable). Disclaimer: I am very much a noob when it comes to Linux, but generally comfortable compiling things and editing code, fiddling with configs, etc.