Thermal framework today supports monitoring for rising temperatures and subsequently initiating cooling action in case of a thermal trip point being crossed. There are scenarios where a SoC need warming mitigating action to be activated if the temperature falls below a cetain permissible limit. Since warming action can be considered mirror opposite of cooling action, most of the thermal framework can be re-used to achieve this. The key assumption in this patch series is that a device can act either as a warming device or a cooling device and not as both. In order to support warming three extensions are needed in the thermal framework. 1. Indication that a trip point is being monitored for falling temperature and not rising temperature. We discussed two different ways to achieve this during LPC. First option is to introduce a new trip type to indicate that a trip is a cold trip(THERMAL_TRIP_COLD). The second option is to introduce a new property for trip point that will indicate whether a trip point is being monitored for rising temperature or falling temperature. The patch series(patches 1-4) chooses the second approach since it allows trip points of any type to be monitored for rising or falling temperature.Also this was the preferred approach when discussed during LPC. The approach that introduces a new cold trip type was posted on the list earlier as a RFC and can be found at [1]. 2. Extend the exisitng governors to handle monitoring of falling temperature. The patch series(patches 5 & 6) extends the step wise governor to monitor the falling temperature.Other governors return doing nothing if the trip point they are being called for is being monitored for falling temperature. The governors' mitigate function is called "throttle" in the thermal framework and with this patch series it is a misnomer as the function is called for both throttling and warming up. Ideally "throttle" should be renamed to "mitigate" to improve readability of code. The renaming is not part of this series. 3. Finally, the cooling device framework itself can be reused for a warming device. As stated before a device can act either as a warming device or a cooling device and not as both. With this the cooling state in the framework can be considered as mitigating state with 0 as the state with no thermal mitigation and higher the number higher the thermal mitigation. Again what affects the code readability and comprehension is the term "cooling" which is a misnomer here. Ideally the term "cooling" should be renamed to "mitigating" and hence thermal_cooling_device will become thermal_mitgating_device. The renaming is not part of the patch series as even though the renaming is a simple search-replace, it will change a lot of files. The patch series(patches 7 & 8) instead introduces a minimal set of _warming_device_ apis to register and unregister warming devices which internally is identical to the _cooling_device_ counterpart. 1. https://lkml.org/lkml/2020/7/10/639 Thara Gopinath (8): dt-bindings: thermal: Introduce monitor-falling parameter to thermal trip point binding thermal: Introduce new property monitor_type for trip point. thermal: thermal_of: Extend thermal dt driver to support bi-directional monitoring of a thermal trip point. thermal:core:Add genetlink notifications for monitoring falling temperature thermal: gov_step_wise: Extend thermal step-wise governor to monitor falling temperature. thermal: Modify thermal governors to do nothing for trip points being monitored for falling temperature thermal:core: Add is_warming_dev and supporting warming device api's to the cooling dev framework. soc:qcom:qcom_aoss: Change cooling_device_register to warming_device_register .../bindings/thermal/thermal-zones.yaml | 7 ++ drivers/soc/qcom/qcom_aoss.c | 6 +- drivers/thermal/gov_bang_bang.c | 12 ++ drivers/thermal/gov_fair_share.c | 12 ++ drivers/thermal/gov_power_allocator.c | 12 ++ drivers/thermal/gov_step_wise.c | 62 +++++++--- drivers/thermal/thermal_core.c | 113 +++++++++++++++--- drivers/thermal/thermal_core.h | 2 + drivers/thermal/thermal_of.c | 22 ++++ include/linux/thermal.h | 9 ++ include/uapi/linux/thermal.h | 5 + 11 files changed, 226 insertions(+), 36 deletions(-) -- 2.25.1
