Re: short-circuit and over-current IRQs

From: Mark Brown <broonie@kernel.org>
To: AngeloGioacchino Del Regno  <angelogioacchino.delregno@somainline.org>
Cc: matti.vaittinen@fi.rohmeurope.com,
	"lgirdwood@gmail.com" <lgirdwood@gmail.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: short-circuit and over-current IRQs
Date: Wed, 27 Jan 2021 16:32:18 +0000	[thread overview]
Message-ID: <20210127163218.GD4387@sirena.org.uk> (raw)
In-Reply-To: <c10cf8d6-f36a-60f4-93cc-807e11a7cec9@somainline.org>

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On Wed, Jan 27, 2021 at 03:34:46PM +0100, AngeloGioacchino Del Regno wrote:
> Il 27/01/21 13:56, Matti Vaittinen ha scritto:

> > I can only speak for BD9576MUF - which has two limits for monitored
> > entity (temperature/voltage). One limit being 'warning' limit (or
> > 'detection' as data-sheet says), the other being 'protection' limit.

> I would tend to agree with you here, Matti. Also from what I understand,
> the wanted outcome is software handling a possibly temporary issue with
> you charging caps, external IC initialization using (expectedly) much
> more power than needed before stabilizing, and eventually handling other
> "real" issues for which there is a solution that may not even include
> disabling the regulator itself, but some other handling on the connected
> device driver.

Note that the events the API currently has are expected to be for the
actual error conditions, not for the warning ones - indicating that the
voltage is out of regulation for example.  If you're supporting warning
notifications as well you'll want to add more events (or possibly
another flag to munge in with the existing events to indicate that it's
a warning rather than an error).

> Though, Mark: for example, on qcom labibb, there's "PBS" that is killing
> the regulators on short-circuit condition and as you see, handling that
> is a little trickier compared to the over-current one, where there is no
> such auto-magic-thing...
> .... I wouldn't know if it'd be a good idea to have a system like qcom's
> PBS everywhere.
> For the sake of protecting HW "paranoidly" though.. maybe :))

Well, if these things are kicking in the hardware is in serious trouble
anyway so it's unclear what the system would be likely to do in
software, and also unclear how safe it is to rely on software to be able
to take that action given that it let things get into such a bad state
in the first place.

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