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9befea3013
Platform Temperature Control is a dynamic control loop implemented in hardware to manage the skin or any board temperature of a device. The reported skin or board temperature is controlled by comparing to a configured target temperature and adjusting the SoC (System on Chip) performance accordingly. The feature supports up to three platform sensors. OEMs (Original Equipment Manufacturers) can configure this feature through the BIOS and provide temperature input directly to the hardware via the Platform Environment Control Interface (PECI). As a result, this feature can operate independently of any OS-level control. The OS interface can be used to further fine-tune the default OEM configuration. Here are some scenarios where the OS interface is beneficial: Verification of Firmware Control: Check if firmware-based control is enabled. If it is, thermal controls from the OS/user space can be backed out. Adjusting Target Limits: While OEMs can set an aggressive target limit, the OS can adjust this to a less aggressive limit based on operating modes or conditions. Given that this is platform temperature control, it is expected that a single user-level manager owns and manages the controls. If multiple user-level software applications attempt to write different targets, it can lead to unexpected behavior. For instance, on a Linux desktop, the Linux thermal daemon can manage these temperature controls, as it has access to all other temperature control settings. The hardware control interface is via MMIO offsets in the processor thermal device MMIO space. There are three instances of MMIO registers. Refer to the platform_temperature_control.c for MMIO details. Expose "enable" and "temperature_target" via sysfs. There are three instances of this controls. So up to three different sensors can be controlled independently. Sysfs interface: tree /sys/bus/pci/devices/0000\:00\:04.0/ptc_?_control/ /sys/bus/pci/devices/0000:00:04.0/ptc_0_control/ ├── enable └── temperature_target /sys/bus/pci/devices/0000:00:04.0/ptc_1_control/ ├── enable └── temperature_target /sys/bus/pci/devices/0000:00:04.0/ptc_2_control/ ├── enable └── temperature_target Description of attributes: Enable: 1 for enable, 0 for disable. This attribute can be used to read the current status. User space can write 0 or 1 to disable or enable this feature respectively. temperature_target: Target temperature limit to which hardware will try to limit in milli degree C. Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> Link: https://patch.msgid.link/20250429000110.236243-2-srinivas.pandruvada@linux.intel.com Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.