linux-kernel - Re: [PATCH v7 3/7] power: reset: Introduce PSCR Recording Framework for Non-Volatile Storage

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Message-ID: <Z9ly2eC0_r3gyToy@pengutronix.de>
Date: Tue, 18 Mar 2025 14:19:21 +0100
From: Oleksij Rempel <o.rempel@...gutronix.de>
To: Matti Vaittinen <mazziesaccount@...il.com>
Cc: 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>,
	chrome-platform@...ts.linux.dev,
	Ahmad Fatoum <a.fatoum@...gutronix.de>,
	"Rafael J. Wysocki" <rafael@...nel.org>, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>, kernel@...gutronix.de,
	Søren Andersen <san@...v.dk>,
	Guenter Roeck <groeck@...omium.org>,
	Zhang Rui <rui.zhang@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Lukasz Luba <lukasz.luba@....com>
Subject: Re: [PATCH v7 3/7] power: reset: Introduce PSCR Recording Framework
 for Non-Volatile Storage

On Tue, Mar 18, 2025 at 01:01:30PM +0200, Matti Vaittinen wrote:
> On 18/03/2025 11:47, Oleksij Rempel wrote:
> > This commit introduces the Power State Change Reasons Recording (PSCRR)
> > framework into the kernel. The framework is vital for systems where
> > PMICs or watchdogs cannot provide information on power state changes. It
> > stores reasons for system shutdowns and reboots, like under-voltage or
> > software-triggered events, in non-volatile hardware storage. This
> > approach is essential for postmortem analysis in scenarios where
> > traditional storage methods (block devices, RAM) are not feasible. The
> > framework aids bootloaders and early-stage system components in recovery
> > decision-making, although it does not cover resets caused by hardware
> > issues like system freezes or watchdog timeouts.
> 
> We might want to rephrase this if we envision that boot reason could be read
> from PMICs (or other devices able to store the boot reason) using PSCRR
> interface. (Because a few PMICs can store the boot reason even for the
> hardware initiated shutdowns like Watchdog or voltage/current protection).

ack.

> > It is primarily intended for controlled power
> > +	  state transitions.
> > +
> > +	  If unsure, say N.
> > diff --git a/drivers/power/reset/Makefile b/drivers/power/reset/Makefile
> > index 10782d32e1da..dbd6ae6b26a4 100644
> > --- a/drivers/power/reset/Makefile
> > +++ b/drivers/power/reset/Makefile
> > @@ -32,6 +32,7 @@ obj-$(CONFIG_POWER_RESET_KEYSTONE) += keystone-reset.o
> >   obj-$(CONFIG_POWER_RESET_SYSCON) += syscon-reboot.o
> >   obj-$(CONFIG_POWER_RESET_SYSCON_POWEROFF) += syscon-poweroff.o
> >   obj-$(CONFIG_POWER_RESET_RMOBILE) += rmobile-reset.o
> > +obj-$(CONFIG_PSCRR) += pscrr.o
> >   obj-$(CONFIG_REBOOT_MODE) += reboot-mode.o
> >   obj-$(CONFIG_SYSCON_REBOOT_MODE) += syscon-reboot-mode.o
> >   obj-$(CONFIG_POWER_RESET_SC27XX) += sc27xx-poweroff.o
> > diff --git a/drivers/power/reset/pscrr.c b/drivers/power/reset/pscrr.c
> > new file mode 100644
> > index 000000000000..466eca0e4f7f
> > --- /dev/null
> > +++ b/drivers/power/reset/pscrr.c
> > @@ -0,0 +1,417 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * pscrr_core.c - Core Power State Change Reason Recording
> > + *
> > + * This framework provides a method for recording the cause of the last system
> > + * reboot, particularly in scenarios where **hardware protection events** (e.g.,
> > + * undervoltage, overcurrent, thermal shutdown) force an immediate reset.
> 
> Is this contradicting the Kconfig / commit message?

There is so many redundant text, i already lost track of it.  What do
you mean?

> 
> > Unlike
> > + * traditional logging mechanisms that rely on block storage (e.g., NAND, eMMC),
> > + * PSCRR ensures shutdown reasons are preserved in a way that survives power
> > + * loss for later analysis.
> 
> Here, the 'level of power-loss' plays a role, right? I assume some level of
> power must be retained for the 'storage' to stay alive.

Yes, on the system I'm working on, there is designed capacity and
voltage drop detector to do $THINGS before the system will go off. To
get the full picture you may take a look to following patches:

https://lore.kernel.org/all/20231026144824.4065145-1-o.rempel@pengutronix.de
https://lore.kernel.org/all/20250310102229.381887-1-o.rempel@pengutronix.de

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