linux-kernel - Re: [PATCH v2 08/12] regulator: allow user configuration of hardware protection action

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Message-ID: <Z433WMKjFx7KJJqN@google.com>
Date: Mon, 20 Jan 2025 07:12:24 +0000
From: Tzung-Bi Shih <tzungbi@...nel.org>
To: Ahmad Fatoum <a.fatoum@...gutronix.de>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Fabio Estevam <festevam@...x.de>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Zhang Rui <rui.zhang@...el.com>, Lukasz Luba <lukasz.luba@....com>,
	Jonathan Corbet <corbet@....net>, Serge Hallyn <serge@...lyn.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>,
	Matti Vaittinen <mazziesaccount@...il.com>,
	Benson Leung <bleung@...omium.org>,
	Guenter Roeck <groeck@...omium.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	chrome-platform@...ts.linux.dev, devicetree@...r.kernel.org,
	kernel@...gutronix.de
Subject: Re: [PATCH v2 08/12] regulator: allow user configuration of hardware
 protection action

On Mon, Jan 13, 2025 at 05:25:33PM +0100, Ahmad Fatoum wrote:
> When the core detects permanent regulator hardware failure or imminent
> power failure of a critical supply, it will call hw_protection_shutdown
> in an attempt to do a limited orderly shutdown followed by powering off
> the system.
> 
> This doesn't work out well for many unattended embedded systems that don't
> have support for shutdown and that power on automatically when power is
> supplied:
> 
>   - A brief power cycle gets detected by the driver
>   - The kernel powers down the system and SoC goes into shutdown mode
>   - Power is restored
>   - The system remains oblivious to the restored power
>   - System needs to be manually power cycled for a duration long enough
>     to drain the capacitors
> 
> Allow users to fix this by calling the newly introduced
> hw_protection_trigger() instead: This way the hw_protection commandline
> or sysfs parameter is used to dictate the policy of dealing with the
> regulator fault.
> 
> Signed-off-by: Ahmad Fatoum <a.fatoum@...gutronix.de>

Reviewed-by: Tzung-Bi Shih <tzungbi@...nel.org>