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Message-ID: <20250520062707.1657667-1-fj5851bi@fujitsu.com> Date: Tue, 20 May 2025 15:27:04 +0900 From: Shinji Nomoto <fj5851bi@...itsu.com> To: Jean Delvare <jdelvare@...e.com>, Guenter Roeck <linux@...ck-us.net>, Jonathan Corbet <corbet@....net>, linux-hwmon@...r.kernel.org, linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, Shinji Nomoto <fj5851bi@...itsu.com> Subject: [PATCH v2] 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. ----- Here are the differences from the previous patch: * Added a note to the "Module Parameters" description regarding systems that do not support power capping. The previous post can be found at: https://lore.kernel.org/linux-hwmon/20250519072756.1512244-1-fj5851bi@fujitsu.com/T/#u Signed-off-by: Shinji Nomoto <fj5851bi@...itsu.com> --- Documentation/hwmon/acpi_power_meter.rst | 29 +++++++++++++++++++++--- 1 file changed, 26 insertions(+), 3 deletions(-) diff --git a/Documentation/hwmon/acpi_power_meter.rst b/Documentation/hwmon/acpi_power_meter.rst index 8628c1161015..a91403a2a26f 100644 --- a/Documentation/hwmon/acpi_power_meter.rst +++ b/Documentation/hwmon/acpi_power_meter.rst @@ -37,9 +37,16 @@ arbitrary strings that ACPI provides with the meter. The measures/ directory contains symlinks to the devices that this meter measures. 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 -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 +the case, the `power[1-*]_cap` and related sysfs files will appear. +For information on enabling the power cap feature, refer to the description +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 hardware has taken action to reduce power consumption. Most likely this will result in reduced performance. @@ -52,3 +59,19 @@ follows: `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 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. -- 2.43.0
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