| ===================================================================== |
| Platform Profile Selection (e.g. /sys/firmware/acpi/platform_profile) |
| ===================================================================== |
| |
| On modern systems the platform performance, temperature, fan and other |
| hardware related characteristics are often dynamically configurable. The |
| platform configuration is often automatically adjusted to the current |
| conditions by some automatic mechanism (which may very well live outside |
| the kernel). |
| |
| These auto platform adjustment mechanisms often can be configured with |
| one of several platform profiles, with either a bias towards low power |
| operation or towards performance. |
| |
| The purpose of the platform_profile attribute is to offer a generic sysfs |
| API for selecting the platform profile of these automatic mechanisms. |
| |
| Note that this API is only for selecting the platform profile, it is |
| NOT a goal of this API to allow monitoring the resulting performance |
| characteristics. Monitoring performance is best done with device/vendor |
| specific tools such as e.g. turbostat. |
| |
| Specifically when selecting a high performance profile the actual achieved |
| performance may be limited by various factors such as: the heat generated |
| by other components, room temperature, free air flow at the bottom of a |
| laptop, etc. It is explicitly NOT a goal of this API to let userspace know |
| about any sub-optimal conditions which are impeding reaching the requested |
| performance level. |
| |
| Since numbers on their own cannot represent the multiple variables that a |
| profile will adjust (power consumption, heat generation, etc) this API |
| uses strings to describe the various profiles. To make sure that userspace |
| gets a consistent experience the sysfs-platform_profile ABI document defines |
| a fixed set of profile names. Drivers *must* map their internal profile |
| representation onto this fixed set. |
| |
| If there is no good match when mapping then a new profile name may be |
| added. Drivers which wish to introduce new profile names must: |
| |
| 1. Explain why the existing profile names canot be used. |
| 2. Add the new profile name, along with a clear description of the |
| expected behaviour, to the sysfs-platform_profile ABI documentation. |
