Merge tag 'thermal-5.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

Pull thermal control updates from Rafael Wysocki:
 "As far as new functionality is concerned, there is a new thermal
  driver for the Intel Hardware Feedback Interface (HFI) along with some
  intel-speed-select utility changes to support it. There are also new
  DT compatible strings for a couple of platforms, and thermal zones on
  some platforms will be registered as HWmon sensors now.

  Apart from the above, some drivers are updated (fixes mostly) and
  there is a new piece of documentation for the Intel DPTF (Dynamic
  Power and Thermal Framework) sysfs interface.

  Specifics:

   - Add a new thermal driver for the Intel Hardware Feedback Interface
     (HFI) including the HFI initialization, HFI notification interrupt
     handling and sending CPU capabilities change messages to user space
     via the thermal netlink interface (Ricardo Neri, Srinivas
     Pandruvada, Nathan Chancellor, Randy Dunlap).

   - Extend the intel-speed-select utility to handle out-of-band CPU
     configuration changes and add support for the CPU capabilities
     change messages sent over the thermal netlink interface by the new
     HFI thermal driver to it (Srinivas Pandruvada).

   - Convert the DT bindings to yaml format for the Exynos platform and
     fix and update the MAINTAINERS file for this driver (Krzysztof
     Kozlowski).

   - Register the thermal zones as HWmon sensors for the QCom's Tsens
     driver and TI thermal platforms (Dmitry Baryshkov, Romain Naour).

   - Add the msm8953 compatible documentation in the bindings (Luca
     Weiss).

   - Add the sm8150 platform support to the QCom LMh driver's DT binding
     (Thara Gopinath).

   - Check the command result from the IPC command to the BPMP in the
     Tegra driver (Mikko Perttunen).

   - Silence the error for normal configuration where the interrupt is
     optionnal in the Broadcom thermal driver (Florian Fainelli).

   - Remove remaining dead code from the TI thermal driver (Yue
     Haibing).

   - Don't use bitmap_weight() in end_power_clamp() in the powerclamp
     driver (Yury Norov).

   - Update the OS policy capabilities handshake in the int340x thermal
     driver (Srinivas Pandruvada).

   - Increase the policies bitmap size in int340x (Srinivas Pandruvada).

   - Replace acpi_bus_get_device() with acpi_fetch_acpi_dev() in the
     int340x thermal driver (Rafael Wysocki).

   - Check for NULL after calling kmemdup() in int340x (Jiasheng Jiang).

   - Add Intel Dynamic Power and Thermal Framework (DPTF) kernel
     interface documentation (Srinivas Pandruvada).

   - Fix bullet list warning in the thermal documentation (Randy
     Dunlap)"

* tag 'thermal-5.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: (30 commits)
  thermal: int340x: Update OS policy capability handshake
  thermal: int340x: Increase bitmap size
  Documentation: thermal: DPTF Documentation
  MAINTAINERS: thermal: samsung: update Krzysztof Kozlowski's email
  thermal/drivers/ti-soc-thermal: Remove unused function ti_thermal_get_temp()
  thermal/drivers/brcmstb_thermal: Interrupt is optional
  thermal: tegra-bpmp: Handle errors in BPMP response
  drivers/thermal/ti-soc-thermal: Add hwmon support
  dt-bindings: thermal: tsens: Add msm8953 compatible
  dt-bindings: thermal: Add sm8150 compatible string for LMh
  thermal/drivers/qcom/lmh: Add support for sm8150
  thermal/drivers/tsens: register thermal zones as hwmon sensors
  MAINTAINERS: thermal: samsung: Drop obsolete properties
  dt-bindings: thermal: samsung: Convert to dtschema
  tools/power/x86/intel-speed-select: v1.12 release
  tools/power/x86/intel-speed-select: HFI support
  tools/power/x86/intel-speed-select: OOB daemon mode
  thermal: intel: hfi: INTEL_HFI_THERMAL depends on NET
  thermal: netlink: Fix parameter type of thermal_genl_cpu_capability_event() stub
  thermal: Replace acpi_bus_get_device()
  ...

2 files changed, 73 insertions, 0 deletions

diff --git a/Documentation/x86/index.rst b/Documentation/x86/index.rst
index f498f1d36cd3..982c8af853b9 100644
--- a/Documentation/x86/index.rst
+++ b/Documentation/x86/index.rst
@@ -21,6 +21,7 @@ x86-specific Documentation
    tlb
    mtrr
    pat
+   intel-hfi
    intel-iommu
    intel_txt
    amd-memory-encryption
diff --git a/Documentation/x86/intel-hfi.rst b/Documentation/x86/intel-hfi.rst
new file mode 100644
index 000000000000..49dea58ea4fb
--- /dev/null
+++ b/Documentation/x86/intel-hfi.rst
@@ -0,0 +1,72 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+============================================================
+Hardware-Feedback Interface for scheduling on Intel Hardware
+============================================================
+
+Overview
+--------
+
+Intel has described the Hardware Feedback Interface (HFI) in the Intel 64 and
+IA-32 Architectures Software Developer's Manual (Intel SDM) Volume 3 Section
+14.6 [1]_.
+
+The HFI gives the operating system a performance and energy efficiency
+capability data for each CPU in the system. Linux can use the information from
+the HFI to influence task placement decisions.
+
+The Hardware Feedback Interface
+-------------------------------
+
+The Hardware Feedback Interface provides to the operating system information
+about the performance and energy efficiency of each CPU in the system. Each
+capability is given as a unit-less quantity in the range [0-255]. Higher values
+indicate higher capability. Energy efficiency and performance are reported in
+separate capabilities. Even though on some systems these two metrics may be
+related, they are specified as independent capabilities in the Intel SDM.
+
+These capabilities may change at runtime as a result of changes in the
+operating conditions of the system or the action of external factors. The rate
+at which these capabilities are updated is specific to each processor model. On
+some models, capabilities are set at boot time and never change. On others,
+capabilities may change every tens of milliseconds. For instance, a remote
+mechanism may be used to lower Thermal Design Power. Such change can be
+reflected in the HFI. Likewise, if the system needs to be throttled due to
+excessive heat, the HFI may reflect reduced performance on specific CPUs.
+
+The kernel or a userspace policy daemon can use these capabilities to modify
+task placement decisions. For instance, if either the performance or energy
+capabilities of a given logical processor becomes zero, it is an indication that
+the hardware recommends to the operating system to not schedule any tasks on
+that processor for performance or energy efficiency reasons, respectively.
+
+Implementation details for Linux
+--------------------------------
+
+The infrastructure to handle thermal event interrupts has two parts. In the
+Local Vector Table of a CPU's local APIC, there exists a register for the
+Thermal Monitor Register. This register controls how interrupts are delivered
+to a CPU when the thermal monitor generates and interrupt. Further details
+can be found in the Intel SDM Vol. 3 Section 10.5 [1]_.
+
+The thermal monitor may generate interrupts per CPU or per package. The HFI
+generates package-level interrupts. This monitor is configured and initialized
+via a set of machine-specific registers. Specifically, the HFI interrupt and
+status are controlled via designated bits in the IA32_PACKAGE_THERM_INTERRUPT
+and IA32_PACKAGE_THERM_STATUS registers, respectively. There exists one HFI
+table per package. Further details can be found in the Intel SDM Vol. 3
+Section 14.9 [1]_.
+
+The hardware issues an HFI interrupt after updating the HFI table and is ready
+for the operating system to consume it. CPUs receive such interrupt via the
+thermal entry in the Local APIC's Local Vector Table.
+
+When servicing such interrupt, the HFI driver parses the updated table and
+relays the update to userspace using the thermal notification framework. Given
+that there may be many HFI updates every second, the updates relayed to
+userspace are throttled at a rate of CONFIG_HZ jiffies.
+
+References
+----------
+
+.. [1] https://www.intel.com/sdm