linux-kernel - [PATCH v3 03/12] docs: thermal: sync hardware protection doc with code

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Message-Id: <20250217-hw_protection-reboot-v3-3-e1c09b090c0c@pengutronix.de>
Date: Mon, 17 Feb 2025 21:39:43 +0100
From: Ahmad Fatoum <a.fatoum@...gutronix.de>
To: 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>, 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, Ahmad Fatoum <a.fatoum@...gutronix.de>
Subject: [PATCH v3 03/12] docs: thermal: sync hardware protection doc with
 code

Originally, the thermal framework's only hardware protection action was
to trigger a shutdown. This has been changed a little over a year ago to
also support rebooting as alternative hardware protection action.

Update the documentation to reflect this.

Fixes: 62e79e38b257 ("thermal/thermal_of: Allow rebooting after critical temp")
Reviewed-by: Tzung-Bi Shih <tzungbi@...nel.org>
Reviewed-by: Matti Vaittinen <mazziesaccount@...il.com>
Signed-off-by: Ahmad Fatoum <a.fatoum@...gutronix.de>
---
 Documentation/driver-api/thermal/sysfs-api.rst | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/Documentation/driver-api/thermal/sysfs-api.rst b/Documentation/driver-api/thermal/sysfs-api.rst
index c803b89b7248f9f26ac24608b0144db5e9c2ddb4..f73de211bdced452b578fb77fb8707b8e59c9180 100644
--- a/Documentation/driver-api/thermal/sysfs-api.rst
+++ b/Documentation/driver-api/thermal/sysfs-api.rst
@@ -413,18 +413,21 @@ This function serves as an arbitrator to set the state of a cooling
 device. It sets the cooling device to the deepest cooling state if
 possible.

-5. thermal_emergency_poweroff
-=============================
+5. Critical Events
+==================

-On an event of critical trip temperature crossing the thermal framework
-shuts down the system by calling hw_protection_shutdown(). The
-hw_protection_shutdown() first attempts to perform an orderly shutdown
-but accepts a delay after which it proceeds doing a forced power-off
-or as last resort an emergency_restart.
+On an event of critical trip temperature crossing, the thermal framework
+will trigger a hardware protection power-off (shutdown) or reboot,
+depending on configuration.
+
+At first, the kernel will attempt an orderly power-off or reboot, but
+accepts a delay after which it proceeds to do a forced power-off or
+reboot, respectively. If this fails, ``emergency_restart()`` is invoked
+as last resort.

 The delay should be carefully profiled so as to give adequate time for
-orderly poweroff.
+orderly power-off or reboot.

-If the delay is set to 0 emergency poweroff will not be supported. So a
-carefully profiled non-zero positive value is a must for emergency
-poweroff to be triggered.
+If the delay is set to 0, the emergency action will not be supported. So a
+carefully profiled non-zero positive value is a must for the emergency
+action to be triggered.

-- 
2.39.5