Re: [PATCH v15 07/14] firmware: psci: Implement vendor-specific resets as reboot-mode

[Umang Chheda <umang.chheda@oss.qualcomm.com>]

On 9/22/2025 7:10 PM, Shivendra Pratap wrote:
> SoC vendors have different types of resets which are controlled
> through various hardware registers. For instance, Qualcomm SoC
> may have a requirement that reboot with “bootloader” command
> should reboot the device to bootloader flashing mode and reboot
> with “edl” should reboot the device into Emergency flashing mode.
> Setting up such reboots on Qualcomm devices can be inconsistent
> across SoC platforms and may require setting different HW
> registers, where some of these registers may not be accessible to
> HLOS. These knobs evolve over product generations and require
> more drivers. PSCI spec defines, SYSTEM_RESET2, vendor-specific
> reset which can help align this requirement. Add support for PSCI
> SYSTEM_RESET2, vendor-specific resets and align the implementation
> to allow user-space initiated reboots to trigger these resets.
> 
> Implement the PSCI vendor-specific resets by registering to the
> reboot-mode framework. As psci init is done at early kernel init,
> reboot-mode registration cannot be done at the time of psci init.
> This is because reboot-mode creates a “reboot-mode” class for
> exposing sysfs, which can fail at early kernel init. To overcome
> this, introduce a late_initcall to register PSCI vendor-specific
> resets as reboot modes. Implement a reboot-mode write function
> that sets reset_type and cookie values during the reboot notifier
> callback.  Introduce a firmware-based call for SYSTEM_RESET2
> vendor-specific reset in the psci_sys_reset path, using
> reset_type and cookie if supported by secure firmware. Register a
> panic notifier and clear vendor_reset valid status during panic.
> This is needed for any kernel panic that occurs post
> reboot_notifiers.
> 
> By using the above implementation, userspace will be able to issue
> such resets using the reboot() system call with the "*arg"
> parameter as a string based command. The commands can be defined
> in PSCI device tree node under “reboot-mode” and are based on the
> reboot-mode based commands.
> 
> Signed-off-by: Shivendra Pratap <shivendra.pratap@oss.qualcomm.com>
> ---
>  drivers/firmware/psci/Kconfig |  2 +
>  drivers/firmware/psci/psci.c  | 89 ++++++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 90 insertions(+), 1 deletion(-)
> 

Reviewed-by: Umang Chheda <umang.chheda@oss.qualcomm.com>

Thanks,
Umang