linux-kernel - Re: [PATCH v17 07/12] firmware: psci: Implement vendor-specific resets as reboot-mode

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Message-ID: <aSc2Yh3AvLXOBvcz@lpieralisi>
Date: Wed, 26 Nov 2025 18:18:26 +0100
From: Lorenzo Pieralisi <lpieralisi@...nel.org>
To: Shivendra Pratap <shivendra.pratap@....qualcomm.com>
Cc: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
	Bjorn Andersson <andersson@...nel.org>,
	Sebastian Reichel <sre@...nel.org>, Rob Herring <robh@...nel.org>,
	Sudeep Holla <sudeep.holla@....com>,
	Souvik Chakravarty <Souvik.Chakravarty@....com>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Andy Yan <andy.yan@...k-chips.com>,
	Mark Rutland <mark.rutland@....com>, Arnd Bergmann <arnd@...db.de>,
	Konrad Dybcio <konradybcio@...nel.org>,
	cros-qcom-dts-watchers@...omium.org, Vinod Koul <vkoul@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Moritz Fischer <moritz.fischer@...us.com>,
	John Stultz <john.stultz@...aro.org>,
	Matthias Brugger <matthias.bgg@...il.com>,
	Krzysztof Kozlowski <krzk@...nel.org>,
	Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
	Mukesh Ojha <mukesh.ojha@....qualcomm.com>,
	Stephen Boyd <swboyd@...omium.org>,
	Andre Draszik <andre.draszik@...aro.org>,
	Kathiravan Thirumoorthy <kathiravan.thirumoorthy@....qualcomm.com>,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-arm-msm@...r.kernel.org,
	Elliot Berman <quic_eberman@...cinc.com>,
	Xin Liu <xin.liu@....qualcomm.com>,
	Srinivas Kandagatla <srini@...nel.org>,
	Umang Chheda <umang.chheda@....qualcomm.com>,
	Nirmesh Kumar Singh <nirmesh.singh@....qualcomm.com>
Subject: Re: [PATCH v17 07/12] firmware: psci: Implement vendor-specific
 resets as reboot-mode

On Wed, Nov 19, 2025 at 05:32:42PM +0530, Shivendra Pratap wrote:
> 
> 
> On 11/19/2025 3:07 PM, Lorenzo Pieralisi wrote:
> > On Tue, Nov 18, 2025 at 11:11:33PM +0530, Shivendra Pratap wrote:
> > 
> > [...]
> > 
> >>> Yes this could be a potential way forward but that's decoupled from the
> >>> options below. If we take this route PSCI maintainers should be added
> >>> as maintainers for this reboot mode driver.
> >>
> >> you mean the new psci_reset driver? yes. Maintainer would be PSCI maintainer,
> >> if we create a new  psci_reset reboot mode driver.
> > 
> > Yes.
> > 
> >>>> - struct with pre-built psci reset_types - (warm, soft, cold). Currently
> >>>>   only two modes supported, anything other than warm/soft defaults to cold.
> >>>> - vendor resets to be added as per vendor choice, inside psci device tree(SOC specific).
> >>>> - psci_reset registers with reboot-mode for registering  vendor resets. Here, we
> >>>>   have a problem, the pre-built psci reset_types - (warm, soft, cold) cannot be added via
> >>>>   reboot-mode framework.
> >>>
> >>> Why ?
> >>
> >> If we want the new psci_reset to take the reboot-mode framework route, is it ok to
> >> add default modes (warm, cold) in the device tree?
> >> If not, then the design of reboot-mode framework(power:reset:reboot-mode.c) needs to be
> >> further changed to equip this new feature. 
> > 
> > Well, yes, all it needs to do is allowing prepopulated reboot modes on top
> > of which DT based ones are added.
> 
> The mode-cold , adds a third variable to reboot-modes as the first parameter for 
> invoke_psci_fn is different for cold vs warm/vendor.
> 
> cold reset call       : invoke_psci_fn(PSCI_0_2_FN_SYSTEM_RESET, 0, 0, 0);
> vendor/warm reset call: invoke_psci_fn(PSCI_FN_NATIVE(1_1, SYSTEM_RESET2), vendor, cookiee, 0);
> 
> Each mode will have 3 argument - like:
> _ _ _ _ _ _ _ _ _ _ _ _ _  _ _ _ _ _ _ 
> MODE   , cold reset, reset_type, cookie
> _ _ _ _ _ _ _ _ _ _ _ _ _  _ _ _ _ _ _ - 
> COLD   ,   1       ,    0      ,     0
> WARM   ,   0       ,    0      ,     0
> vendor1,   0       ,0x80000000 ,     1
> vendor2,   0       ,0x80000010 ,     0
> 
> So reboot-mode framework will now define and support upto three 32 bit arguments for each mode?

The cookie value is unused for SYSTEM_WARM_RESET, you can encode there whether
it is a cold (SYSTEM_RESET) or warm (SYSTEM_RESET2 - SYSTEM_WARM_RESET) architectural
reset when the magic value(aka reset_type) == 0x0 ?

The reboot mode parameters do not necessarily need to map to PSCI function
calls parameters - provided we define that explicitly.

Lorenzo