Luke Ross

Linx 820

4 commits linx820-master-2018-11-05.tar.gz git clone https://lukeross.name/projects/linx820.git/

Notes on running Linux on a Linx 820 tablet.

master /

README.md Updates for 4.19 a month ago

README.md

# linx-820

Notes on running Linux on a Linx 820 tablet; I'm using Ubuntu Artful.

## BIOS

Hold down Volume-Up whilst turning on. From here you can turn off secure boot
(you need a keyboard plugged in, F8? I think to save changes).

## Installing Ubunu

Write the image to an SD card. Enter BIOS and pick the SD card off the
boot menu. It'll stop at the Grub prompt; enter:

```
set root=(hd1)
configfile /boot/grub/grub.cfg
```

It'll then be fine. I suggest not removing the two recovery partitions;
just replace the Windows install.

Install `haveged` and set it to start on startup or else the system
will run out of entropy during gdm startup. This happens after a few
boots - or switch to lightdm.

## Display

Intel graphics (PCI). Mostly worked with no configuration including micro-HDMI
(but no sound).
However the backlight will not come on and/or Xorg will crash unless you
put these into /etc/initramfs.conf/modules:

```
overlay
pwm-lpss
pwm-lpss-platform
```

After doing this, run `update-initramfs -u`.
https://linuxiumcomau.blogspot.co.uk/2017/05/gui-isorespinsh.html
will take care of this for you.

*Warning*: Upgrades to initramfs tend to wipe this file, causing gdm to not
start on the next reboot. This can include any updates installed during
the installation process!

## Touchscreen

Goodix Capacitive TouchScreen (i2c). Needed no configuration

## Wifi

Intel Corporation Wireless 3165 (PCI). Needed no configuration

## Bluetooth

Intel Bluetooth (USB). Needed no configuration

## Speakers

LPE + RT5651. These work since kernel 4.19.0.

## Headphone socket

The HDMI sound driver currently causes PulseAudio to crash; disable it
by adding an entry into modprobe.conf:

```
blacklist snd_hdmi_lpe_audio
```

I also need the UCM information for the `bytcr-rt5651` from
https://github.com/plbossart/UCM

From kernel 4.17 jack-detect works properly.

## HDMI audio

Not yet working; might be better when PulseAudio release the fix
for crash detailed in the headphones section.

## Accelerometer

MIRAMEMS da280 (i2c). da280 driver works from kernel 4.16 or use
the patch from
https://www.spinics.net/lists/linux-iio/msg36010.html

Also needed a udev hardware DB entry (or else the vertical
display is flipped):

```
sensor:modalias:acpi:MIRAACC*:*
 ACCEL_MOUNT_MATRIX=1, 0, 0; 0, -1, 0; 0, 0, 1
```

## USB (both as host and device)

PCI.  It's `xhci` for the host most and `dwc3-pci` as a gadget.

Prior to 4.17 it'll work in whatever mode you boot it in, and won't change
afterwards (affecting charging). There's some support in 4.17 for
mode change, and by 4.18 it seems to work pretty reliably.

## Camera

2 x OV2680 (i2c via ISP). The AtomISP driver was removed from staging
but didn't seem to work anyway. OV2680 drivers have recently been
checked into the kernel tree but I've not tested to see if they work
without the AtomISP driver.

## Charging LED

Not yet known. I2C?

## TPM

Not tested

## Suspend

Surprisingly, seems to work fine. However the power button on wake-up tends to immediately sleep
the device again. I set the power button to not sleep to avoid this.