[Letux-kernel] Pyra charging

[H. Nikolaus Schaller]

Hi,
I have a new observation. While testing the new mipi display driver
the battery drained completely and the Pyra was shut down (by Palmas).

Then I connected the charger to the USB port. Charging (and the Pyra)
started for a short time (LED goes red).

After a while the Pyra went off again, even with USB cable connected.
And the red LED turned off. At ca. 30°C. So no over/under temperature.

Now the interesting observation: even unplugging and replugging
the USB cable did not (re)start charging to let the LED go red.

What I had to do was to unplug USB and remove the battery. After that,
the Pyra was constantly charging for ca. 4-5 hours until the battery
became full. Even while I turned on/off/reboot the Pyra while continuing
my tests.

Now the new idea: does this have something to do with the "safety
timer?". Should we restart it to trigger a new charging sequence?
Does it stop every further charging attempt once expired?

I am not even sure if the safety timer can be reset by software.

If not, we may have to use the bq2429x watchdog which resets the
chip (like unplugging the battery) if the OMAP isn't retriggering
it every now and then. This would also have the benefit that the
chip falls in a well defined state if we turn the OMAP off which
does not depend on what the bq driver did in the past minutes.

I have some (untested/incomplete/experimental) bq2429x watchdog
extension which I have attached.

Discussion of this topic is welcome.

BR,
Nikolaus

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