So now 10 weeks later I'm happy to report that after spending a lot of my spare time on kernel fixes I've it mostly working, specifically I've fixed the following things:
1) Brightness control
2) Wifi no longer working with recent kernels
3) Suspend/resume not working
4) Power and volume up/down buttons not working
5) System not waking up when opening the lid
6) Not charging when the power cable gets plugged in after boot
7) Only drawing max 0.5A from the charger, charging slowly if at all
8) Battery monitoring
And Takashi Iwai and Adrian Plazas have fixed:
9) Headphone jack detection
I've done my best to fix all of these properly and I've been submitting patches for all of this upstream. About half of the patches have already been accepted and will be merged into the kernel for the 4.12 release.
If you want to give it a try here are some step-by-step instructions:
1) First of all if you still have Windows on there and you've the 20161118 BIOS you may want to consider downgrading the BIOS to the 20161025 version before wiping Windows. The 20161118 BIOS is locked in a sort of novice mode and removes all options from the BIOS. Since Windows does not support USB gadget mode the dwc3 gadget controller is disabled and cannot be re-enabled in the 20161118 BIOS. So if you want to be able to use the USB-C connector in gadget/device mode and not just as a charging or host port in the future you are going to need the 20161025 BIOS and BIOS-flashing is only supported under Windows (flashrom may work but I was not brave enough to try it).
2) Install your favorite distro, either use an external hdmi monitor or add "i915.modeset=0 fbcon=rotate:1" to the kernel cmdline
3) To get wifi to work copy this file to /lib/firmware/brcm and then reboot.
If you kernel is new enough it will trip over a BIOS bug which causes the wifi chip to get disabled, you can "fix" the BIOS bug (if you do not have
the 20161118 BIOS) by changing the following BIOS setting: "Chipset" -> "South Bridge" -> "LPSS & SCC Configuration" -> "SCC SDIO Support"
to "Disabled". My patches include a workaround for the BIOS bug which works with the 20161118 BIOS, so if you've that you will need to install my kernel through other means (e.g. an USB network adapter).
4) clone my personal linux kernel repo:
git clone https://github.com/jwrdegoede/linux-sunxi.git
This comes with a kernel .config file based on the standard Fedora kernel config (so highly modular). Follow the usual instructions for your distro to build a kernel from source (minus getting the .config). Make sure an initrd gets generated, this kernel-config will not work without an initrd.
Before rebooting into the new kernel add the following to the kernel cmdline in your grub configuration: "fbcon=rotate:1 dmi_product_name=GPD-WINI55".
For brightness control to work your initrd must include the pwm-lpss and pwm-lpss-platform modules. Under Fedora you can do this by booting into the new kernel and then running:
dracut -f --add-drivers "pwm-lpss pwm-lpss-platform" /boot/initramfs-$(uname -r).img $(uname -r)
5) To get sound to work you need to do some userspace config tweaks:
Edit /etc/pulse/daemon.conf and set: "realtime-scheduling = no" to work around a pulse issue with the hdmi-audio support for Cherry Trail.
Create an /usr/share/alsa/ucm/chtrt5645 directory and copy the 2 .conf files from here into that dir.
6) Edit /lib/udev/hwdb.d/99-local.hwdb, add:
ACCEL_MOUNT_MATRIX=-1, 0, 0; 0, -1, 0; 0, 0, 1
Copy this file to /lib/udev/rules.d/
Then run "sudo udevadm hwdb --update" and reboot, together with a new enough iio-sensor-proxy, this will fix the screen orientation under gdm / gnome (note you need to tilt the device a bit toward you after booting to get it to recognize the screen orientation for now).
7) All done enjoy your (almost) fully functional GPDwin under Linux
Note these instructions are for somewhat advanced Linux users, if you hit problems please take a look at your distro's documentation or ask for help on your distro's forums.
Linux BIOS tweaks, if you have the 20161025 BIOS, there are 2 BIOS tweaks you can do:
1) Enable USB gadget support, goto: "Chipset" -> "South Bridge" -> "USB Configuration" And change the following 2 options:
"USB OTG Support" : "PCI"
"DRD Access Method" : "Mmio"
This will allow you to load gadget drivers (e.g. "modprobe g_serial") and then connect the GPD-win to a PC and have it show up as an usb device
2) Enable the "S5-Charging Driver" some howtos actually advice disabling this, but it is useful to make sure the GPDwin fast charges when plugged into a charger without being turned on (and even allows for faster charging once the OS is booted). The reason some people advice to turn it off is because it causes problems turning the device on when plugged in and fully charged, when plugged in and fully charged it will simply show a "Battery 100%" screen when you turn it on and then turn off again. You can workaround this by pressing ctrl-alt-del while at the "Battery 100%" screen, or not enable the "S5-Charging Driver" and live with the slower charging.
To enable this goto: "Advanced" -> "System Component" and set "S5-Charging Driver" to "Enabled"
1) Recently I found out that the GPDwin has a FUSB300C USB Type-C controller and a PI3USB30532 USB switch which together should allow full USB-C functionality at USB 3.0 speeds (currently the gadget mode runs at 2.0 speed and host mode does not work at all). I plan to write and upstream drivers for this to make this all work.
2) Get all of the required kernel changes upstream.
3) Make things more simple overall ideally new distros released in 2018 will just work without requiring any changes at all.