linux-kernel - Re: [PATCH v7 2/7] reboot: hw_protection_trigger: use standardized numeric shutdown/reboot reasons instead of strings

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Message-ID: <e87c1389-c173-47ee-8b01-cb0764a55afc@gmail.com>
Date: Tue, 18 Mar 2025 13:26:09 +0200
From: Matti Vaittinen <mazziesaccount@...il.com>
To: Oleksij Rempel <o.rempel@...gutronix.de>,
 Sebastian Reichel <sre@...nel.org>,
 Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
 Benson Leung <bleung@...omium.org>, Tzung-Bi Shih <tzungbi@...nel.org>,
 Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: kernel@...gutronix.de, linux-kernel@...r.kernel.org,
 Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>,
 "Rafael J. Wysocki" <rafael@...nel.org>, Zhang Rui <rui.zhang@...el.com>,
 Lukasz Luba <lukasz.luba@....com>, linux-pm@...r.kernel.org,
 Søren Andersen <san@...v.dk>,
 Guenter Roeck <groeck@...omium.org>, Ahmad Fatoum <a.fatoum@...gutronix.de>,
 Andrew Morton <akpm@...ux-foundation.org>, chrome-platform@...ts.linux.dev
Subject: Re: [PATCH v7 2/7] reboot: hw_protection_trigger: use standardized
 numeric shutdown/reboot reasons instead of strings

On 18/03/2025 11:47, Oleksij Rempel wrote:
> Prepares the kernel for the Power State Change Reason (PSCR) recorder,
> which will store shutdown and reboot reasons in persistent storage.
> 
> Instead of using string-based reason descriptions, which are often too
> large to fit within limited storage spaces (e.g., RTC clocks with only 8
> bits of battery-backed storage), we introduce `enum psc_reason`. This
> enumerates predefined reasons for power state changes, making it
> efficient to store and retrieve shutdown causes.
> 
> Key changes:
> - Introduced `enum psc_reason`, defining structured reasons for power state
>    changes.
> - Replaced string-based shutdown reasons with `psc_reason` identifiers.
> - Implemented `get_psc_reason()` and `set_psc_reason()` for tracking the
>    last shutdown cause.
> - Added `psc_reason_to_str()` to map enum values to human-readable strings.
> - Updated `hw_protection_trigger()` to use `psc_reason` instead of string
>    parameters.
> - Updated all consumers of `hw_protection_trigger()` to pass an appropriate
>    `psc_reason` value instead
>    of a string.
> 
> Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>

Reviewed-by: Matti Vaittinen <mazziesaccount@...il.com>

> +
> +/**
> + * enum psc_reason - Enumerates reasons for power state changes.
> + *
> + * This enum defines various reasons why a system might transition into a
> + * shutdown, reboot, or kexec state. While originally intended for hardware
> + * protection events, `psc_reason` can be extended to track other system
> + * transitions, such as controlled reboots triggered by software or
> + * maintenance operations.
> + *
> + * The values in this enumeration provide structured and standardized
> + * identifiers that replace free-form string descriptions. They are designed
> + * to be stored efficiently, making them suitable for use in environments
> + * with limited storage, such as battery-backed RTC registers, non-volatile
> + * memory, or bootloader communication mechanisms.
> + *
> + * Importantly, the order of these values **must remain stable**, as
> + * bootloaders, user-space tools, or post-mortem investigation utilities
> + * may rely on their numerical representation for consistent behavior.

Oh, here is the comment I was asking for in the other patch. So, this is 
all fine - please ignore my comment in the other patch.

> + *
> + * @PSCR_UNKNOWN: Unknown or unspecified reason for the power state change.
> + *	This value serves as a default when no explicit cause is recorded.
> + *
> + * @PSCR_UNDER_VOLTAGE: Shutdown or reboot triggered due to supply voltage
> + *      dropping below a safe threshold. This helps prevent instability or
> + *      corruption caused by insufficient power.
> + *
> + * @PSCR_OVER_CURRENT: System shutdown or reboot due to excessive current draw,
> + *      which may indicate a short circuit, an overloaded power rail, or other
> + *      hardware faults requiring immediate action.
> + *
> + * @PSCR_REGULATOR_FAILURE: A critical failure in a voltage regulator, causing
> + *      improper power delivery. This may be due to internal component failure,
> + *      transient conditions, or external load issues requiring mitigation.
> + *
> + * @PSCR_OVER_TEMPERATURE: System shutdown or reboot due to excessive thermal
> + *	conditions. This attempts to prevent hardware damage when temperature
> + *	sensors detect unsafe levels, often impacting CPUs, GPUs, or power
> + *	components.
> + *
> + * @PSCR_EC_PANIC: Shutdown or reboot triggered by an Embedded Controller (EC)
> + *	panic. The EC is a microcontroller responsible for low-level system
> + *	management, including power sequencing, thermal control, and battery
> + *	management. An EC panic may indicate critical firmware issues, power
> + *	management errors, or an unrecoverable hardware fault requiring
> + *	immediate response.
> + *
> + * @PSCR_REASON_COUNT: Number of defined power state change reasons. This
> + *	value is useful for range checking and potential future extensions
> + *	while maintaining compatibility.
> + */
> +enum psc_reason {
> +	PSCR_UNKNOWN,
> +	PSCR_UNDER_VOLTAGE,
> +	PSCR_OVER_CURRENT,
> +	PSCR_REGULATOR_FAILURE,
> +	PSCR_OVER_TEMPERATURE,
> +	PSCR_EC_PANIC,
> +
> +	/* Number of reasons */
> +	PSCR_REASON_COUNT,
> +};