linux-kernel - Re: [PATCH v2 2/3] hwmon: (pmbus/core): Add regulator event support

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Date:   Wed, 5 Apr 2023 16:19:40 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Matti Vaittinen <mazziesaccount@...il.com>,
        Naresh Solanki <naresh.solanki@...ements.com>,
        linux-hwmon@...r.kernel.org, Jean Delvare <jdelvare@...e.com>,
        Patrick Rudolph <patrick.rudolph@...ements.com>,
        linux-kernel@...r.kernel.org, Sascha Hauer <sha@...gutronix.de>,
        jerome Neanne <jneanne@...libre.com>,
        "Mutanen, Mikko" <Mikko.Mutanen@...rohmeurope.com>
Subject: Re: [PATCH v2 2/3] hwmon: (pmbus/core): Add regulator event support

On Wed, Apr 05, 2023 at 07:18:32AM -0700, Guenter Roeck wrote:

> The consumers for the regulators provided by PMBus devices are the devices
> connected to those PMBus devices, just like with (presumably) every other
> regulator. Not sure why a regulator instantiated by a regulator driver
> would provide a regulator regulating itself.

Some devices have optionally used internal regulators which can also be
left idle with the supply done externally, and it is also very common to
chain LDOs to DCDCs provided by the same chip (DCDCs provide much better
efficiency but have lower quality output so doing most of the voltage
drop with a DCDC then cleaning up the output with a LDO can be an
effective combination).

> Same situation. I though a regulator driver would notify the regulator subsystem
> if it observes a problem with the supplies it regulates, but based on your feedback
> I am not sure anymore what those notifications are supposed to be used for,
> and if such notifications are appropriate. That means I'll have to read up on all
> this, and I don't have the time to do that in the near future given that I am buried
> in pending reviews and the work I am actually getting paid for.

The theory is that if a consumer detects that the device it's
controlling has bad power then it can take corrective action if there's
some specification mandated error handling (for something like a
standard bus) or risk of hardware damage.  It can also try to avoid
interacting with hardware if that might not work.

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