Linux Adding New Thermal Code To Deal With Hot Tegra Devices
Simple CPU throttling isn't sufficient for cooling some NVIDIA Tegra devices running the upstream Linux kernel so thermal cooling integration into the device frequency "devfreq" scaling code is in the work for such high performance NVIDIA SoCs.
Various developers working on the NVIDIA Tegra / Arm Linux support found that some Tegra SoCs / devices are producing much more heat than others. The old ASUS Transformer TF700T with Tegra 3 SoC for example when running the mainline Linux kernel is found to be running very hot and the initial target of these new patches.
While CPU throttling is engaged to help lower the operating temperature, that isn't enough but ultimately with the additional thermal cooling code for the Tegra devfreq, memory frequency down-clocking can also be engaged. With the system memory frequency also being throttled, it appears the temperatures are then more manageable.
One of the patches goes on to explain that memory frequency throttling has a rather large difference with Tegra, "Expose ACTMON devfreq device as a cooling device in order to throttle memory freq on overheat. Throttling of memory freq has a significant cooling effect on NVIDIA Tegra SoCs since higher memory freqs require higher SoC core voltage which is one of the main causes of the heating."
These patches were sent out earlier this month and then picked up already so looks like they will make it for the Linux 5.14 cycle.