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

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Message-ID: <58eb8f0e-a029-cb7f-e63a-9eac6a6444df@oss.qualcomm.com>
Date: Thu, 24 Jul 2025 23:51:23 +0530
From: Shivendra Pratap <shivendra.pratap@....qualcomm.com>
To: Arnd Bergmann <arnd@...db.de>, 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 7/24/2025 8:13 PM, Arnd Bergmann wrote:
> 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.
In current patch, psci driver registers to reboot-mode using a device-tree
node. So reboot-mode does not has a driver name for psci's reboot registration.
its like -  reboot_mode_register(reboot, <struct device_node *np>)

Now when we want to use the registering reboot driver's name for sysfs,
either we- 
1, Pass an explicit name from psci driver(say "psci") while registering
to reboot-mode.
or
2. Create a virtual device in psci driver with name say "psci" and then
register for reboot-mode.

which one is preferred? suggestions? 

> 
> 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");
This will introduce an additional feature in the reboot-mode driver.
If a colon is present in the command like "<driver name>:bootloader",
Call the "<driver name>" specific writes only. 
We want to add this feature? 
> 
>    Arnd