Issue 947: Critical Pyra power management issues

Reported by daveshah, Jul 23, 2020

1. After a charger has been connected and disconnected, the device 
doesn't start charging again when a charger is re-connected unless 
it is reset

2. After a charger has been connected and disconnected, the device 
doesn't want to power off. Shut down in X11 causes a return to the 
login screen; shut down from the command line causes it to hang, 
still powered up, after the final shutdown step. I can't 100% say 
whether this is a userspace, or kernel issue, or both.

3. I saw some freezes with a low battery and 500mA USB port (with a 
proper 2A charger, it seems rock solid) but this may be unavoidable, 
or a totally different issue and the charger was just a red herring.

Some of these may have already been fixed in one of the Pyra 
branches, in which case the fixes need to be forward-ported to 5.6.y 
etc. Posting this so I don't forget about anything.

Comment 1 by daveshah, Jul 23, 2020

There are also two battery devices being incorrectly reported to 
userspace, this was definitely fixed in ToastBucket's kernel and the 
fix needs to be added to Letux.

Comment 2 by Nikolaus Schaller, Jul 23, 2020

Having two battery devices is intentional in Letux since there is a 
fuel gauge chip and a gauge based on reading the battery voltage 
(generic-adc-battery). The latter one is less reliable.

It is easy to remove it through CONFIG_GENERIC_ADC_BATTERY=n in the 
pyra_defconfig or add a blacklist entry to /etc/modprobe.d

Charging does IMHO only start if battery is less than ca. 80%. Or, 
there may be an issue with USB plugout/in detection triggering 
restart.

500mA is not enough to operate the OMAP5 (unless we get some deeper 
sleep modes).

Letux Kernel