hwmon: (pmbus/max31785) Add delay between bus accesses

The MAX31785 has shown erratic behaviour across multiple system
designs, unexpectedly clock stretching and NAKing transactions.

Experimentation shows that this seems to be triggered by a register access
directly back to back with a previous register write. Experimentation also
shows that inserting a small delay after register writes makes the issue go
away.

Use a similar solution to what the max15301 driver does to solve the same
problem. Create a custom set of bus read and write functions that make sure
that the delay is added.

Signed-off-by: Lakshmi Yadlapati <lakshmiy@us.ibm.com>
Link: https://lore.kernel.org/r/20231027044346.2167548-1-lakshmiy@us.ibm.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

hwmon: Switch i2c drivers back to use .probe()

After commit b8a1a4cd5a98 ("i2c: Provide a temporary .probe_new()
call-back type"), all drivers being converted to .probe_new() and then
03c835f498b5 ("i2c: Switch .probe() to not take an id parameter") convert
back to (the new) .probe() to be able to eventually drop .probe_new() from
struct i2c_driver.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20230505131718.1210071-1-u.kleine-koenig@pengutronix.de
[groeck: Added missing change in pmbus/acbel-fsg032.c]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

hwmon: (pmbus) Introduce PMBUS symbol namespace

Exported pmbus symbols are only supposed to be used from PMBus code.
Introduce PMBUS symbol namespace to prevent misuse from other code.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>

hwmon: (pmbus/max31785) Support revision "B"

There was an issue in how the tach feedbacks of dual rotor fans were
reported during any change in fan speeds with revision "A" of the
MAX31785. When the fan speeds would transition to a new target speed,
the rotor not wired to the TACH input when TACHSEL = 0 would report a
speed of 0 until the new target was reached. This has been fixed,
resulting in a revision "B" update where the MFR_REVISION of "B" is
0x3061.

Signed-off-by: Matthew Barth <msbarth@linux.ibm.com>
Link: https://lore.kernel.org/r/20210201212217.73721-1-msbarth@linux.ibm.com
[groeck: Change 'ret' variable type to int]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

hwmon: (pmbus) shrink code and remove pmbus_do_remove()

The only action currently performed in pmbus_do_remove() is removing the
debugfs hierarchy. We can schedule a devm action at probe time and remove
pmbus_do_remove() entirely from all pmbus drivers.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Link: https://lore.kernel.org/r/20201026105352.20359-1-brgl@bgdev.pl
[groeck: Removed references to pmbus_do_remove from documentation]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

hwmon (pmbus) use simple i2c probe function

pmbus_do_probe doesn't use the id information provided in its second
argument, so this can be removed, which then allows using the
single-parameter i2c probe function ("probe_new") for probes.

This avoids scanning the identifier tables during probes.

Drivers which didn't use the id are converted as-is; drivers which did
are modified as follows:

* if the information in i2c_client is sufficient, that's used instead
(client->name);
* configured v. probed comparisons are performed by comparing the
configured name to the detected name, instead of the ids; this
involves strcmp but is still cheaper than comparing all the device
names when scanning the tables;
* anything else is handled by calling i2c_match_id() with the same
level of error-handling (if any) as before.

Additionally, the mismatch message in the ltc2978 driver is adjusted
so that it no longer assumes that the driver_data is an index into
ltc2978_id.

Signed-off-by: Stephen Kitt <steve@sk2.org>
Acked-by: Wolfram Sang <wsa@kernel.org>
Link: https://lore.kernel.org/r/20200808210004.30880-1-steve@sk2.org
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

hwmon: (pmbus) Add 'phase' parameter where needed for multi-phase support

In preparation for multi-phase support, add 'phase' parameter to read_word
and set_page functions. Actual multi-phase support will be added in
a subsequent patch.

Cc: Vadim Pasternak <vadimp@mellanox.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

hwmon: (pmbus/max31785) Remove a useless #define

There is a typo in MAX37185_NUM_FAN_PAGES. To be consistent, it should be
MAX31785_NUM_FAN_PAGES (1 and 7 switched).

At line 24, we already have:
#define MAX31785_NR_FAN_PAGES 6
and MAX37185_NUM_FAN_PAGES seems to be unused.

It is likely that it is only a typo and/or a left-over.
So, axe it.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/20190721101553.20911-1-christophe.jaillet@wanadoo.fr
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152

Based on 1 normalized pattern(s):

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 of the license or at
your option any later version

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 3029 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070032.746973796@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

hwmon: (max31785) Add OF device ID table

The driver doesn't have a struct of_device_id table but supported devices
are registered via Device Trees. This is working on the assumption that a
I2C device registered via OF will always match a legacy I2C device ID and
that the MODALIAS reported will always be of the form i2c:<device>.

But this could change in the future so the correct approach is to have an
OF device ID table if the devices are registered via OF.

Before this patch:

$ modinfo drivers/hwmon/pmbus/max31785.ko | grep alias
alias: i2c:max31785a
alias: i2c:max31785

After this patch:

$ modinfo drivers/hwmon/pmbus/max31785.ko | grep alias
alias: i2c:max31785a
alias: i2c:max31785
alias: of:N*T*Cmaxim,max31785aC*
alias: of:N*T*Cmaxim,max31785a
alias: of:N*T*Cmaxim,max31785C*
alias: of:N*T*Cmaxim,max31785

Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

hwmon: (pmbus/max31785) Add dual tachometer support

The dual tachometer feature is implemented in hardware with a TACHSEL
input to indicate the rotor under measurement, and exposed on the device
by extending the READ_FAN_SPEED_1 word with two extra bytes*. The need
to read the non-standard four-byte response leads to a cut-down
implementation of i2c_smbus_xfer_emulated() included in the driver.
Further, to expose the second rotor tachometer value to userspace the
values are exposed through virtual pages. We re-route accesses to
FAN_CONFIG_1_2 and READ_FAN_SPEED_1 on pages 23-28 (not defined by the
hardware) to the same registers on pages 0-5, and with the latter command
we extract the value from the second word of the four-byte response.

* The documentation recommends the slower rotor be associated with
TACHSEL=0, which corresponds to the first word of the response. The
TACHSEL=0 measurement is used by the controller's closed-loop fan
management to judge target fan rate.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

hwmon: (pmbus/max31785) Add fan control

The implementation makes use of the new fan control virtual registers
exposed by the pmbus core. It mixes use of the default implementations
with some overrides via the read/write handlers to handle FAN_COMMAND_1
on the MAX31785, whose definition breaks the value range into various
control bands dependent on RPM or PWM mode.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

pmbus: Add driver for Maxim MAX31785 Intelligent Fan Controller

The Maxim MAX31785 is a PMBus device providing closed-loop, multi-channel
fan management with temperature and remote voltage sensing. It supports
various fan control features, including PWM frequency control, temperature
hysteresis, dual tachometer measurements, and fan health monitoring.

This patch presents a basic driver using only the existing features of the
PMBus subsystem.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
[groeck: Modified description to clarify that fan control is not yet provided]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>