Oh dear… so we reverted a change in the EC firmware in this new release that was done in the previous release, more exactly the setting of PL4 of the Intel CPU based on the charger state.
Let’s take a step back for a second. A laptop is a pretty complex system when looking at it from a power consumption standpoint. There are a number of components in that can draw various amounts of power at different times and depending on their use - the main CPU is of course one (15W TDP), the DDR4 RAM, SSD(s), the LCD backlight, WiFi/BT, SD card reader etc. etc. And then there are the external USB port - we have four, two type-A and two type-C ports which can draw significant power if populated. The total power consumption of the device can thus vary a lot.
Coming back to the issue what we tried to do is to set the Intel CPUs PL4 to some sane value when in battery only mode in order not to overload the battery. The battery has a limited power budget which is lower than the total maximum power that can be consumed by the system. In order not to overload the battery we clamped down the Intel CPU’s PL4 to 20W and allowed it to go up to a much higher value when on AC.
Since about the same time we introduced this change we observe two things: 1. the sudden power down seems to be gone (and now reappearing) but worse 2. we also saw quite a number of dying main boards, you probably have read about this too already. In the broken main board in most cases the charging does not work anymore. The boards will still work from battery but will not charge anymore. In the path of the charging current is a main power switching IC that has to regulate the current from the DC charger input to the whole system, i.e. all power supplies plus charging the battery.
These currents are hard to measure, you would have to break up traces etc. to measure individual current flows. My current work hypothesis is that we did set the max power when connected to charger too high and overloaded this switch when the system was under higher load (plus charging) and thus caused the dying main boards.
With reverting this change we may now have some default PL4 (which is badly documented in the Intel docs) which is higher than the battery case we set it to in the previous version and thus the sudden power off happens again. But I hope that the dying main boards do not happen anymore! It may sound a bit crude but for now I prefer system to shut down rather than causing permanent hardware damage.
If during the next couple of weeks we do not see the dying mainboard problems happening anymore we will need to revisit the PL4 settings or other means again.
In the meantime you could also try to limit the CPU power consumption while using it from battery using the PL1 and PL2 settings within Linux:
/sys/devices/virtual/powercap/intel-rapl/intel-rapl:0/constraint_0_power_limit_uw
/sys/devices/virtual/powercap/intel-rapl/intel-rapl:0/constraint_1_power_limit_uw
These two values are for the long term (0 = PL1) and short term (1 = PL2) power budget of the Intel CPU, in µW. The TDP of the 10710U is 15W, PL2 can be something like PL2= PL1 + (PL1 / 3)
With that you can limit the Intel CPUs short and long term average power consumption. In the L14 the default PL1 is 15W and PL2 is 20W, bringing these down by a few Watt should help already, e.g. 10/15W:
echo 10000000 > /sys/devices/virtual/powercap/intel-rapl/intel-rapl:0/constraint_0_power_limit_uw
echo 15000000 > /sys/devices/virtual/powercap/intel-rapl/intel-rapl:0/constraint_1_power_limit_uw
Please accept my apologies for this inconvenience, we are working on it and will implement better / safe defaults as soon as we have narrowed down the reason for the dying main boards, which right now is my primary concern.
Cheers
nicole
They trigger too often or prematurely so I removed that again and that should work better now.
