linux-kernel - Re: [RFC PATCH v1 7/7] thermal: core: set Power State Change Reason before hw_protection

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Message-ID: <CAJZ5v0jvJa-TaB_ifNdDCDMLozAuX=e7ddgUcU1tx_3Rzp3rcA@mail.gmail.com>
Date: Fri, 19 Jan 2024 21:11:57 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Oleksij Rempel <o.rempel@...gutronix.de>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, devicetree@...r.kernel.org, 
	Conor Dooley <conor+dt@...nel.org>, Daniel Lezcano <daniel.lezcano@...aro.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Liam Girdwood <lgirdwood@...il.com>, 
	Mark Brown <broonie@...nel.org>, Sebastian Reichel <sre@...nel.org>, linux-kernel@...r.kernel.org, 
	Søren Andersen <san@...v.dk>, 
	Rob Herring <robh+dt@...nel.org>, Srinivas Kandagatla <srinivas.kandagatla@...aro.org>, 
	kernel@...gutronix.de, linux-pm@...r.kernel.org, 
	Zhang Rui <rui.zhang@...el.com>, Lukasz Luba <lukasz.luba@....com>
Subject: Re: [RFC PATCH v1 7/7] thermal: core: set Power State Change Reason
 before hw_protection_shutdown()

On Fri, Jan 19, 2024 at 8:34 PM Oleksij Rempel <o.rempel@...gutronix.de> wrote:
>
> On Fri, Jan 19, 2024 at 07:34:26PM +0100, Rafael J. Wysocki wrote:
> > On Fri, Jan 19, 2024 at 2:25 PM Oleksij Rempel <o.rempel@...gutronix.de> wrote:
> > >
> > > Store the state change reason to some black box for later investigation.
> >
> > Seriously?
> >
> > What black box, where, how this is useful and who is going to use it,
> > pretty please.
>
> The 'black box' refers to a non-volatile memory (NVMEM) cell used by the
> Power State Change Reasons (PSCR) framework. This cell stores reasons
> for sudden power state changes, like voltage drops or over-temperature
> events. This data is invaluable for post-mortem analysis to understand
> system failures or abrupt shutdowns. It's particularly useful for
> systems where PMICs or watchdogs cannot record such events. The data can
> inform recovery routines in the bootloader or early kernel stages during
> subsequent boots, enhancing system reliability and aiding in debugging
> and diagnostics.

OK, so please add all of the above to the patch changelog.