linux-kernel - Re: [PATCH v4 1/5] dt-bindings: mfd: rk806: allow to customize PMIC reset mode

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Message-ID: <175105158757.4019943.860671576753586474.robh@kernel.org>
Date: Fri, 27 Jun 2025 14:13:08 -0500
From: "Rob Herring (Arm)" <robh@...nel.org>
To: Quentin Schulz <foss+kernel@...il.net>
Cc: Conor Dooley <conor+dt@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
	Daniel Semkowicz <dse@...umatec.com>,
	Nicolas Frattaroli <nicolas.frattaroli@...labora.com>,
	Sebastian Reichel <sebastian.reichel@...labora.com>,
	linux-arm-kernel@...ts.infradead.org,
	Lukasz Czechowski <lukasz.czechowski@...umatec.com>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	devicetree@...r.kernel.org, linux-rockchip@...ts.infradead.org,
	Heiko Stuebner <heiko@...ech.de>, Lee Jones <lee@...nel.org>,
	Quentin Schulz <quentin.schulz@...rry.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/5] dt-bindings: mfd: rk806: allow to customize PMIC
 reset mode


On Fri, 27 Jun 2025 12:53:53 +0200, Quentin Schulz wrote:
> From: Quentin Schulz <quentin.schulz@...rry.de>
> 
> The RK806 PMIC allows to configure its reset/restart behavior whenever
> the PMIC is reset either programmatically or via some external pins
> (e.g. PWRCTRL or RESETB).
> 
> The following modes exist:
>  - 0; restart PMU,
>  - 1; reset all power off reset registers and force state to switch to
>    ACTIVE mode,
>  - 2; same as mode 1 and also pull RESETB pin down for 5ms,
> 
> For example, some hardware may require a full restart (mode 0) in order
> to function properly as regulators are shortly interrupted in this mode.
> 
> This is the case for RK3588 Jaguar and RK3588 Tiger which have a
> companion microcontroller running on an independent power supply and
> monitoring the PMIC power rail to know the state of the main system.
> When it detects a restart, it resets its own IPs exposed to the main
> system as if to simulate its own reset. Failing to perform this fake
> reset of the microcontroller may break things (e.g. watchdog not
> automatically disabled, buzzer still running until manually disabled,
> leftover configuration from previous main system state, etc...).
> 
> Some other systems may be depending on the power rails to not be
> interrupted even for a small amount of time[1].
> 
> This allows to specify how the PMIC should perform on the hardware level
> and may differ between harwdare designs, so a DT property seems
> warranted. I unfortunately do not see how this could be made generic
> enough to make it a non-vendor property.
> 
> [1] https://lore.kernel.org/linux-rockchip/2577051.irdbgypaU6@workhorse/
> 
> Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> Signed-off-by: Quentin Schulz <quentin.schulz@...rry.de>
> ---
>  .../devicetree/bindings/mfd/rockchip,rk806.yaml     | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 

Reviewed-by: Rob Herring (Arm) <robh@...nel.org>