linux-kernel - Re: [PATCH v12 0/8] Implement vendor resets for PSCI SYSTEM

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Message-Id: <36f62026-9517-42bd-8f9a-92f39fcdc136@app.fastmail.com>
Date: Thu, 24 Jul 2025 16:43:48 +0200
From: "Arnd Bergmann" <arnd@...db.de>
To: "Shivendra Pratap" <shivendra.pratap@....qualcomm.com>,
 "Krzysztof Kozlowski" <krzk@...nel.org>,
 "Florian Fainelli" <florian.fainelli@...adcom.com>,
 "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>,
 "Lorenzo Pieralisi" <lpieralisi@...nel.org>,
 "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>
Cc: "Dmitry Baryshkov" <dmitry.baryshkov@....qualcomm.com>,
 "Mukesh Ojha" <mukesh.ojha@....qualcomm.com>,
 "Stephen Boyd" <swboyd@...omium.org>,
 André Draszik <andre.draszik@...aro.org>,
 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>,
 "Srinivas Kandagatla" <srini@...nel.org>,
 "Elliot Berman" <elliot.berman@....qualcomm.com>,
 "Konrad Dybcio" <konrad.dybcio@....qualcomm.com>
Subject: Re: [PATCH v12 0/8] Implement vendor resets for PSCI SYSTEM_RESET2

On Thu, Jul 24, 2025, at 16:04, Shivendra Pratap wrote:
> On 7/24/2025 6:18 PM, Krzysztof Kozlowski wrote:
>> On 24/07/2025 14:24, Shivendra Pratap wrote:

>> I strongly insist using compatible as way to find your device, not node
>> names.
> It will look better to switch to compatible. Will define a compatible for
> psci reboot-mode binding and align the patch to use the compatible for sysfs.
> Current patch defines reboot-mode as a property to psci, hope its fine to
> define a compatible for this property like "psci-vendor-reset" or
> "psci-reboot-modes"?
>

How about using the reboot driver name as the identifier in sysfs
instead of the compatible string? That would make it independent of
devicetree.

I had a related idea to provide some namespacing on the actual
reboot syscall parameter, as we have two (or more) orthogonal
concepts here, when there is more than one reboot driver and
drivers support multiple modes.

E.g. you could use

    syscall(__NR_reboot, LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, 
            LINUX_REBOOT_CMD_RESTART2, "watchdog");

vs

    syscall(__NR_reboot, LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, 
            LINUX_REBOOT_CMD_RESTART2, "psci");

to pick one of the drivers, or

    syscall(__NR_reboot, LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, 
            LINUX_REBOOT_CMD_RESTART2, "bootloader");

    syscall(__NR_reboot, LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, 
            LINUX_REBOOT_CMD_RESTART2, "recovery");

to ask for a reboot from any driver that supports a mode, or
combine the two and ask a specific mode in a specific driver like

    syscall(__NR_reboot, LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, 
            LINUX_REBOOT_CMD_RESTART2, "psci:bootloader");

   Arnd