linux-kernel - Re: [PATCH v2 2/4] dt-bindings: arm: Document reboot mode magic

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Date: Tue, 16 Apr 2024 15:32:02 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Sudeep Holla <sudeep.holla@....com>
Cc: Elliot Berman <quic_eberman@...cinc.com>, Bjorn Andersson <andersson@...nel.org>, 
	Konrad Dybcio <konrad.dybcio@...aro.org>, Sebastian Reichel <sre@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	Vinod Koul <vkoul@...nel.org>, Andy Yan <andy.yan@...k-chips.com>, 
	Lorenzo Pieralisi <lpieralisi@...nel.org>, Mark Rutland <mark.rutland@....com>, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>, 
	Satya Durga Srinivasu Prabhala <quic_satyap@...cinc.com>, Melody Olvera <quic_molvera@...cinc.com>, 
	Shivendra Pratap <quic_spratap@...cinc.com>, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	Florian Fainelli <florian.fainelli@...adcom.com>, linux-pm@...r.kernel.org, 
	linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v2 2/4] dt-bindings: arm: Document reboot mode magic

On Tue, 16 Apr 2024 at 12:30, Sudeep Holla <sudeep.holla@....com> wrote:
>
> On Sun, Apr 14, 2024 at 12:30:25PM -0700, Elliot Berman wrote:
> > Add bindings to describe vendor-specific reboot modes. Values here
> > correspond to valid parameters to vendor-specific reset types in PSCI
> > SYSTEM_RESET2 call.
> >
>
> IIUC, PSCI SYSTEM_RESET will be always supported, so the choice of using
> SYSTEM_RESET2 sounds like a system policy and must not have any information
> in the device tree. All required support from PSCI is discoverable and
> the policy choice must be userspace driven. That's my opinion.

Well, we are talking about the vendor-specific resets, which are not
discoverable. The spec defines them as "implementation defined".
For example, PCSI spec doesn't define a way to add "reset to
bootloader" or "reset to recovery" kinds of resets.

I think the bindings at least should make it clear that the vendor bit
it being set automatically. I won't comment whether this is a good
decision or not.

-- 
With best wishes
Dmitry