.. SPDX-License-Identifier: GPL-2.0

Kernel driver max20826
======================

Supported chips:

  * Analog Devices MAX20826

    Prefix: 'max20826'

    Addresses scanned: -

    Datasheet: Datasheet is not publicly available.

  * Analog Devices MAX20855B

    Prefix: 'max20855b'

    Addresses scanned: -

    Datasheet: Datasheet is not publicly available.

  * Analog Devices MAX20908

    Prefix: 'max20908'

    Addresses scanned: -

    Datasheet: Datasheet is not publicly available.

  * Analog Devices MAX20912

    Prefix: 'max20912'

    Addresses scanned: -

    Datasheet: Datasheet is not publicly available.

  * Analog Devices MAX20916

    Prefix: 'max20916'

    Addresses scanned: -

    Datasheet: Datasheet is not publicly available.

Author:

  - Nuno Sá <nuno.sa@analog.com>


Description
-----------

This driver supports hardware monitoring for Analog Devices MAX20826,
MAX20855B, MAX20908, MAX20912, and MAX20916 multiphase voltage regulator
controllers with PMBus interface.

The devices are dual-loop, multiphase controllers. Depending on the device and
configuration, the high-speed processor voltage-control interface can be
Nvidia PWMVID, Intel SVID, AMD SVI3, or AVSBus. PMBus is used for monitoring,
configuration, status, and fault reporting.

The driver detects whether the device uses PMBus page mode or direct address
mode. In direct address mode, rail B is accessed at the rail A I2C address plus
one. If rail B is present, the driver exposes a second PMBus page.

The driver detects the active number of phases and exposes per-phase input and
output current attributes through the PMBus virtual phase support.

Usage Notes
-----------

This driver does not auto-detect devices. You will have to instantiate the
devices explicitly. Please see Documentation/i2c/instantiating-devices.rst for
details.

The optional ``avren`` and ``bvren`` GPIOs may be provided to control the rail A
and rail B hardware enable pins. If regulator support is enabled, the rails are
also registered through the PMBus regulator framework.

The source of the output voltage of each rail, i.e. either the high-speed
processor voltage-control interface or PMBus, is normally selected once, before
the processor boots. Hence it is described in firmware with the
``adi,rail-a-high-speed`` and ``adi,rail-b-high-speed`` properties. If the
property is not given for a rail, PMBus controls its output voltage.

Sysfs entries
-------------

The following attributes are supported. Limits, alarms, and per-phase entries
are exposed depending on device capabilities, rail configuration, and detected
phase count.

=========================== ================================================
in1_label                   "vin"
in1_input                   Measured input voltage
in1_alarm                   Input voltage alarm
in[2-3]_label               "vout[1-2]"
in[2-3]_input               Measured output voltage
in[2-3]_alarm               Output voltage alarm
currX_label                 "iinN", "iinN.P", "ioutN", or "ioutN.P"
currX_input                 Measured input/output current
currX_alarm                 Current alarm
powerX_label                "pinN" or "poutN"
powerX_input                Measured input/output power
temp[1-2]_input             Measured temperature
temp[1-2]_alarm             Temperature alarm
=========================== ================================================

Notes
-----

``N`` is the rail number, starting at 1. ``P`` is the phase number, starting at
0. The exact ``currX`` indices depend on the number of present rails and on the
detected phase count.

Debugfs entries
---------------

In addition to the entries provided by the PMBus core, the following entries are
available for debug purposes only. They are not part of any ABI and may change
or go away at any time.

=========================== ================================================
in[2-3]_high_speed_en       Enable high-speed voltage-control interface
in_high_speed_bus           Active high-speed voltage-control interface
=========================== ================================================

``in[2-3]_high_speed_en`` is a per-rail read/write entry matching the standard
hwmon voltage channels for the output rails. ``in2_high_speed_en`` controls rail
A / ``vout1``. ``in3_high_speed_en`` controls rail B / ``vout2`` and is only
present if rail B is detected. Writing 1 selects the high-speed voltage-control
interface for that rail; writing 0 selects PMBus voltage control.

``in_high_speed_bus`` is a read-only entry reporting the high-speed interface
used by the device, for example ``Nvidia PWMVID``, ``Intel SVID``, ``AMD SVI3``,
or ``AVSBus``.