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doc: hwmon: acpi_power_meter: Add information about enabling the power capping feature. 

To enable the power capping feature of the acpi_power_meter driver on
systems other than IBM products, you must explicitly specify
the force_cap_on module parameter.

Add information to the documentation about enabling the power capping
feature with this driver, including the above, to improve user convenience.

Signed-off-by: Shinji Nomoto <fj5851bi@fujitsu.com>
Link: https://lore.kernel.org/r/20250520062707.1657667-1-fj5851bi@fujitsu.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Shinji Nomoto 2025-05-20 15:27:04 +09:00 committed by Guenter Roeck
parent b2446a16db
commit 46d40b2479
1 changed files with 26 additions and 3 deletions
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29
Documentation/hwmon/acpi_power_meter.rst
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@ -37,9 +37,16 @@ arbitrary strings that ACPI provides with the meter. The measures/ directory
contains symlinks to the devices that this meter measures. contains symlinks to the devices that this meter measures.
Some computers have the ability to enforce a power cap in hardware. If this is Some computers have the ability to enforce a power cap in hardware. If this is
the case, the `power[1-*]_cap` and related sysfs files will appear. When the the case, the `power[1-*]_cap` and related sysfs files will appear.
average power consumption exceeds the cap, an ACPI event will be broadcast on For information on enabling the power cap feature, refer to the description
the netlink event socket and a poll notification will be sent to the of the "force_on_cap" option in the "Module Parameters" chapter.
To use the power cap feature properly, you need to set appropriate value
(in microWatts) to the `power[1-*]_cap` sysfs files.
The value must be within the range between the minimum value at `power[1-]_cap_min`
and the maximum value at `power[1-]_cap_max (both in microWatts)`.
When the average power consumption exceeds the cap, an ACPI event will be
broadcast on the netlink event socket and a poll notification will be sent to the
appropriate `power[1-*]_alarm` file to indicate that capping has begun, and the appropriate `power[1-*]_alarm` file to indicate that capping has begun, and the
hardware has taken action to reduce power consumption. Most likely this will hardware has taken action to reduce power consumption. Most likely this will
result in reduced performance. result in reduced performance.
@ -52,3 +59,19 @@ follows:
`power[1-*]_cap` will be notified if the firmware changes the power cap. `power[1-*]_cap` will be notified if the firmware changes the power cap.
`power[1-*]_interval` will be notified if the firmware changes the averaging `power[1-*]_interval` will be notified if the firmware changes the averaging
interval. interval.
Module Parameters
-----------------
* force_cap_on: bool
Forcefully enable the power capping feature to specify
the upper limit of the system's power consumption.
By default, the driver's power capping feature is only
enabled on IBM products.
Therefore, on other systems that support power capping,
you will need to use the option to enable it.
Note: power capping is potentially unsafe feature.
Please check the platform specifications to make sure
that capping is supported before using this option.