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

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Message-ID: <eb123791-a63d-4a59-a8c2-e7716201d976@gmail.com>
Date: Wed, 22 Jan 2025 13:18:31 +0200
From: Matti Vaittinen <mazziesaccount@...il.com>
To: Ahmad Fatoum <a.fatoum@...gutronix.de>,
 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>,
 Benson Leung <bleung@...omium.org>, Tzung-Bi Shih <tzungbi@...nel.org>,
 Guenter Roeck <groeck@...omium.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>
Cc: 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 13/01/2025 18:25, 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: Matti Vaittinen <mazziesaccount@...il.com>