linux-kernel - Re: [PATCH v2 2/2] regulator: fixed: add support for under-voltage IRQ

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Message-ID: <471281bf-4126-496b-93ef-0807f4910ce7@sirena.org.uk>
Date:   Tue, 24 Oct 2023 14:26:24 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Oleksij Rempel <o.rempel@...gutronix.de>
Cc:     Liam Girdwood <lgirdwood@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>, kernel@...gutronix.de,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 2/2] regulator: fixed: add support for under-voltage
 IRQ

On Tue, Oct 24, 2023 at 03:08:42PM +0200, Oleksij Rempel wrote:

> Add interrupt support for under-voltage notification. This functionality
> can be used on systems capable to detect under-voltage state and having
> enough capacity to let the SoC do some emergency preparation.
> 
> This change enforce default policy to shutdown system as soon as
> interrupt is triggered.

...

> +static irqreturn_t reg_fixed_under_voltage_irq_handler(int irq, void *data)
> +{
> +	hw_protection_shutdown("Critical voltage drop reached",
> +			       FV_DEF_EMERG_SHUTDWN_TMO);
> +
> +	return IRQ_HANDLED;
> +}

We need a bit more policy here - the regulator could be critical to
system function but it could also be well isolated and just affecting
whatever device it's directly supplying in a way that the system can
tolerate and might even want to (eg, for something like a SD card or USB
port where end users are plugging in external hardware).

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