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Diffstat (limited to 'Documentation')
3 files changed, 107 insertions, 1 deletions
diff --git a/Documentation/admin-guide/pm/intel_uncore_frequency_scaling.rst b/Documentation/admin-guide/pm/intel_uncore_frequency_scaling.rst index 5ab3440e6cee..5151ec312dc0 100644 --- a/Documentation/admin-guide/pm/intel_uncore_frequency_scaling.rst +++ b/Documentation/admin-guide/pm/intel_uncore_frequency_scaling.rst @@ -113,3 +113,62 @@ to apply at each uncore* level. Support for "current_freq_khz" is available only at each fabric cluster level (i.e., in uncore* directory). + +Efficiency vs. Latency Tradeoff +------------------------------- + +The Efficiency Latency Control (ELC) feature improves performance +per watt. With this feature hardware power management algorithms +optimize trade-off between latency and power consumption. For some +latency sensitive workloads further tuning can be done by SW to +get desired performance. + +The hardware monitors the average CPU utilization across all cores +in a power domain at regular intervals and decides an uncore frequency. +While this may result in the best performance per watt, workload may be +expecting higher performance at the expense of power. Consider an +application that intermittently wakes up to perform memory reads on an +otherwise idle system. In such cases, if hardware lowers uncore +frequency, then there may be delay in ramp up of frequency to meet +target performance. + +The ELC control defines some parameters which can be changed from SW. +If the average CPU utilization is below a user-defined threshold +(elc_low_threshold_percent attribute below), the user-defined uncore +floor frequency will be used (elc_floor_freq_khz attribute below) +instead of hardware calculated minimum. + +Similarly in high load scenario where the CPU utilization goes above +the high threshold value (elc_high_threshold_percent attribute below) +instead of jumping to maximum uncore frequency, frequency is increased +in 100MHz steps. This avoids consuming unnecessarily high power +immediately with CPU utilization spikes. + +Attributes for efficiency latency control: + +``elc_floor_freq_khz`` + This attribute is used to get/set the efficiency latency floor frequency. + If this variable is lower than the 'min_freq_khz', it is ignored by + the firmware. + +``elc_low_threshold_percent`` + This attribute is used to get/set the efficiency latency control low + threshold. This attribute is in percentages of CPU utilization. + +``elc_high_threshold_percent`` + This attribute is used to get/set the efficiency latency control high + threshold. This attribute is in percentages of CPU utilization. + +``elc_high_threshold_enable`` + This attribute is used to enable/disable the efficiency latency control + high threshold. Write '1' to enable, '0' to disable. + +Example system configuration below, which does following: + * when CPU utilization is less than 10%: sets uncore frequency to 800MHz + * when CPU utilization is higher than 95%: increases uncore frequency in + 100MHz steps, until power limit is reached + + elc_floor_freq_khz:800000 + elc_high_threshold_percent:95 + elc_high_threshold_enable:1 + elc_low_threshold_percent:10 diff --git a/Documentation/devicetree/bindings/platform/microsoft,surface-sam.yaml b/Documentation/devicetree/bindings/platform/microsoft,surface-sam.yaml new file mode 100644 index 000000000000..b33d26f15b2a --- /dev/null +++ b/Documentation/devicetree/bindings/platform/microsoft,surface-sam.yaml @@ -0,0 +1,47 @@ +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) +%YAML 1.2 +--- +$id: http://devicetree.org/schemas/platform/microsoft,surface-sam.yaml# +$schema: http://devicetree.org/meta-schemas/core.yaml# + +title: Surface System Aggregator Module (SAM, SSAM) + +maintainers: + - Konrad Dybcio <konradybcio@kernel.org> + +description: | + Surface devices use a standardized embedded controller to let the + operating system interface with various hardware functions. The + specific functionalities are modeled as subdevices and matched on + five levels: domain, category, target, instance and function. + +properties: + compatible: + const: microsoft,surface-sam + + interrupts: + maxItems: 1 + + current-speed: true + +required: + - compatible + - interrupts + +additionalProperties: false + +examples: + - | + #include <dt-bindings/interrupt-controller/irq.h> + uart { + embedded-controller { + compatible = "microsoft,surface-sam"; + + interrupts-extended = <&tlmm 91 IRQ_TYPE_EDGE_RISING>; + + pinctrl-0 = <&ssam_state>; + pinctrl-names = "default"; + + current-speed = <4000000>; + }; + }; diff --git a/Documentation/devicetree/bindings/serial/serial.yaml b/Documentation/devicetree/bindings/serial/serial.yaml index 30c85768d980..6aa9cfae417b 100644 --- a/Documentation/devicetree/bindings/serial/serial.yaml +++ b/Documentation/devicetree/bindings/serial/serial.yaml @@ -88,7 +88,7 @@ properties: TX FIFO threshold configuration (in bytes). patternProperties: - "^(bluetooth|bluetooth-gnss|gnss|gps|mcu|onewire)$": + "^(bluetooth|bluetooth-gnss|embedded-controller|gnss|gps|mcu|onewire)$": if: type: object then: |