[PATCH v13 07/10] firmware: psci: Implement vendor-specific resets as reboot-mode

[Arnd Bergmann]

On Wed, Jul 30, 2025, at 17:23, André Draszik wrote:
> On Wed, 2025-07-30 at 18:33 +0530, Shivendra Pratap wrote:
>> On 7/30/2025 2:14 PM, André Draszik wrote:

>> 1. For this, both commands will be defined in the psci->reboot-mode DT Node with the arguments that
>>    are defined and supported by the firmware.
>> 2. Further, such requirement will now be taken care by the underlying firmware that supports
>>    PSCI vendor-specific reset. When we call into firmware with vendor specific reset arguments,
>>    firmware will take care of the defined HW writes and warm/cold reset as per the mapping of the
>>    defined arguments. Firmware and the Linux kernel here are in agreement for executing the
>>    vendor-specific resets.
>
> So that means
>
>     echo warm > /sys/kernel/reboot/mode
>     reboot bootloader
>
> and
>
>     echo cold > /sys/kernel/reboot/mode
>     reboot bootloader
>
> can not be distinguished.
>
> The firmware can not know whether or not cold or warm reboot was
> requested in this case by the user.

My feeling is that this is fine: the /sys/kernel/reboot/mode
interface is not really used on anything other than 32-bit
arm and x86 machines, and the way it is specific as
cold/warm/hard/soft/gpio is not that useful.

I think for the purpose of the new code here, we should talk
about reboot "commands" instead of "modes" to avoid confusing
between the global "enum reboot_mode" variable and the
firmware interface for reboot modes as listed in DT.

    Arnd