linux-kernel - Re: About regulator error events

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Message-ID: <Y/yt8nzVuO4sUg3v@sirena.org.uk>
Date:   Mon, 27 Feb 2023 13:19:46 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Sascha Hauer <sha@...gutronix.de>
Cc:     linux-kernel@...r.kernel.org, Liam Girdwood <lgirdwood@...il.com>,
        kernel@...gutronix.de, linux-arm-kernel@...ts.infradead.org,
        Matti Vaittinen <mazziesaccount@...il.com>
Subject: Re: About regulator error events

On Mon, Feb 27, 2023 at 02:05:42PM +0100, Sascha Hauer wrote:
> I have a board here which has some current limited power switches on it
> and I wonder if I can do something reasonable with the error interrupt
> pins these switches have.

Just noticed that Matti (who's been doing a bunch of work here) wasn't
CCed so adding him.

> The devices do not have a communication channel, instead they only have
> an enable pin and an error interrupt pin. See
> https://www.diodes.com/assets/Datasheets/AP22652_53_52A_53A.pdf for a
> datasheet.  The devices come in two variants, one goes into current
> limiting mode in case of overcurrent and the other variant switches off
> until it gets re-enabled again.
> 
> At first sight it seemed logical to me to wire up the error interrupt
> pins to REGULATOR_EVENT_OVER_CURRENT events. That was easy to do, but
> now the question is: What can a regulator consumer do with these events?
> 
> The strategy I had in mind was to disable the regulator, enable it again
> to see if the errors persists and if it does, permanently disable the
> device.  Disabling the regulator only works though when there's only one
> consumer.  With multiple consumers only the enable count decreases, but
> the regulator itself stays enabled. This means implementing such a
> policy at the consumer side is not generally possible. Implementing a
> policy in the regulator core seems awkward as well, as a good strategy
> likely differs between different consumers.
> 
> A first good step might be to notify the user somehow. While we can get
> the overcurrent status of a regulator from
> /sys/class/regulator/*/over_current there doesn't seem to be any way to
> get a regulator event in userspace, right?  Would patches changing that
> be welcomed?
> 
> There doesn't seem to be much prior art for handling regulator error
> events in the kernel. It would be great to get some input what others do
> in this situation, or to get some ideas what they would do if they had
> the time to do so ;)
> 
> Sascha
> 
> -- 
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