The following series provides a new way to cool down a SoC by reducing the dissipated power on the CPUs. Based on the initial work from Kevin Wangtao, the series implements a CPU cooling device based on idle injection, relying on the cpuidle framework and a combo CPU cooling device combining the cooling effect of the cpufreq and the cpuidle cooling device with the objective of getting the advantages of both.
The patchset is designed to have the current DT binding for the cpufreq cooling device to be compatible with the new cooling devices. Different cpu cooling devices can not co-exist on the system, the cpu cooling device is enabled or not, and one cooling strategy is selected (cpufreq, cpuidle or both with the combo). It is not possible to have all of them available at the same time. This series is divided into three parts. The first part just provides trivial changes for the copyright and removes an unused field in the cpu freq cooling device structure. The second part provides the idle injection cooling device, allowing a SoC without a cpufreq driver to use this cooling device as an alternative. The third part provides the combo idle injection and frequency cooling device. The preliminary benchmarks show the following changes: On the hikey6220, dhrystone shows a throughtput increase of 40% for an increase of the latency of 16% while sysbench shows a latency increase of 5%. On a hikey3660, the combo cooling device shows an improvement in term of throughput for the little cluster of 5% and a decrease of 5% on the big cluster. However, the hikey3660 support in mainline is still experimental and there is no guarantee the numberis provided in the DT are accurate enough. Daniel Lezcano (9): thermal/drivers/cpu_cooling: Fixup the header and copyright thermal/drivers/cpu_cooling: Add Software Package Data Exchange (SPDX) thermal/drivers/cpu_cooling: Remove pointless field thermal/drivers/Kconfig: Convert the CPU cooling device to a choice thermal/drivers/cpu_cooling: Introduce the cpu idle cooling driver thermal/drivers/cpu_cooling: Add idle cooling device documentation cpuidle/drivers/cpuidle-arm: Register the cooling device thermal/drivers/cpu_cooling: Add the combo cpu cooling device Documentation/thermal/cpu-idle-cooling.txt | 165 ++++++ drivers/cpuidle/cpuidle-arm.c | 5 + drivers/thermal/Kconfig | 37 +- drivers/thermal/cpu_cooling.c | 869 ++++++++++++++++++++++++++++- include/linux/cpu_cooling.h | 15 +- 6 files changed, 1068 insertions(+), 31 deletions(-) create mode 100644 Documentation/thermal/cpu-idle-cooling.txt -- 2.7.4
