reboot: add support for configuring emergency hardware protection action

We currently leave the decision of whether to shutdown or reboot to
protect hardware in an emergency situation to the individual drivers.

This works out in some cases, where the driver detecting the critical
failure has inside knowledge: It binds to the system management controller
for example or is guided by hardware description that defines what to do.

In the general case, however, the driver detecting the issue can't know
what the appropriate course of action is and shouldn't be dictating the
policy of dealing with it.

Therefore, add a global hw_protection toggle that allows the user to
specify whether shutdown or reboot should be the default action when the
driver doesn't set policy.

This introduces no functional change yet as hw_protection_trigger() has no
callers, but these will be added in subsequent commits.

[arnd@arndb.de: hide unused hw_protection_attr]
  Link: https://lkml.kernel.org/r/20250224141849.1546019-1-arnd@kernel.org
Link: https://lkml.kernel.org/r/20250217-hw_protection-reboot-v3-7-e1c09b090c0c@pengutronix.de
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Reviewed-by: Tzung-Bi Shih <tzungbi@kernel.org>
Cc: Benson Leung <bleung@chromium.org>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Fabio Estevam <festevam@denx.de>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Lukasz Luba <lukasz.luba@arm.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Matteo Croce <teknoraver@meta.com>
Cc: Matti Vaittinen <mazziesaccount@gmail.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Rob Herring (Arm) <robh@kernel.org>
Cc: Rui Zhang <rui.zhang@intel.com>
Cc: Sascha Hauer <kernel@pengutronix.de>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index fb8752b42ec8..b2f04967876f 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1933,6 +1933,12 @@
 			which allow the hypervisor to 'idle' the guest
 			on lock contention.
 
+	hw_protection=	[HW]
+			Format: reboot | shutdown
+
+			Hardware protection action taken on critical events like
+			overtemperature or imminent voltage loss.
+
 	i2c_bus=	[HW]	Override the default board specific I2C bus speed
 				or register an additional I2C bus that is not
 				registered from board initialization code.