Re: [PATCH v12 0/8] Implement vendor resets for PSCI SYSTEM_RESET2

Shivendra Pratap
2025-07-24T12:24:15Z

On 7/24/2025 5:46 AM, Florian Fainelli wrote:
> On 7/21/25 11:28, Shivendra Pratap wrote:
>> The PSCI SYSTEM_RESET2 call allows vendor firmware to define
>> additional reset types which could be mapped to the reboot
>> argument.
>>
>> User-space should be able to reboot a device into different
>> operational boot-states supported by underlying bootloader and
>> firmware. Generally, some HW registers need to be written, based
>> on which the bootloader and firmware decide the next boot state
>> of device, after the reset. For example, a requirement on
>> Qualcomm platforms may state that reboot with "bootloader"
>> command, should reboot the device into bootloader flashing mode
>> and reboot with “edl” command, should reboot the device into an
>> 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 defines a
>> vendor-specific reset in SYSTEM_RESET2 spec, which enables the
>> firmware to take care of underlying setting for any such
>> supported vendor-specific reboot. Qualcomm firmwares are
>> beginning to support and expose PSCI SYSTEM_RESET2
>> vendor-specific reset types to simplify driver requirements from
>> Linux. With such support added in the firmware, we now need a
>> Linux interface which can make use of the firmware calls for PSCI
>> vendor-specific resets. This will align such reboot requirement
>> across platforms and vendors.
>>
>> The current psci driver supports two types of resets –
>> SYSTEM_RESET2 Arch warm-reset and SYSTEM_RESET cold-reset. The
>> patchset introduces the PSCI SYSTEM_RESET2 vendor-specific reset
>> into the reset path of the psci driver and aligns it to work with
>> reboot system call - LINUX_REBOOT_CMD_RESTART2, when used along
>> with a supported string-based command in “*arg”.
>>
>> The patchset uses reboot-mode based commands, to define the
>> supported vendor reset-types commands in psci device tree node
>> and registers these commands with the reboot-mode framework.
>>
>> The PSCI vendor-specific reset takes two arguments, being,
>> reset_type and cookie as defined by the spec. To accommodate this
>> requirement, enhance the reboot-mode framework to support two
>> 32-bit arguments by switching to 64-bit magic values.
>>
>> Along this line, the patchset also extends the reboot-mode
>> framework to add a non-device-based registration function, which
>> will allow drivers to register using device tree node, while
>> keeping backward compatibility for existing users of reboot-mode.
>> This will enable psci driver to register for reboot-mode and
>> implement a write function, which will save the magic and then
>> use it in psci reset path to make a vendor-specific reset call
>> into the firmware. In addition, the patchset will expose a sysfs
>> entry interface within reboot-mode which can be used by userspace
>> to view the supported reboot-mode commands.
>>
>> The list of vendor-specific reset commands remains open due to
>> divergent requirements across vendors, but this can be
>> streamlined and standardized through dedicated device tree
>> bindings.
>>
>> Currently three drivers register with reboot-mode framework -
>> syscon-reboot-mode, nvmem-reboot-mode and qcom-pon. Consolidated
>> list of commands currently added across various vendor DTs:
>>   mode-loader
>>   mode-normal
>>   mode-bootloader
>>   mode-charge
>>   mode-fastboot
>>   mode-reboot-ab-update
>>   mode-recovery
>>   mode-rescue
>>   mode-shutdown-thermal
>>   mode-shutdown-thermal-battery
>>
>> Detailed list of commands being used by syscon-reboot-mode:
>>      arm64/boot/dts/exynos/exynosautov9.dtsi:
>>     mode-bootloader = <EXYNOSAUTOV9_BOOT_BOOTLOADER>;
>>     mode-fastboot = <EXYNOSAUTOV9_BOOT_FASTBOOT>;
>>     mode-recovery = <EXYNOSAUTOV9_BOOT_RECOVERY>;
>>
>>      arm64/boot/dts/exynos/google/gs101.dtsi:
>>          mode-bootloader = <0xfc>;
>>          mode-charge = <0x0a>;
>>          mode-fastboot = <0xfa>;
>>          mode-reboot-ab-update = <0x52>;
>>          mode-recovery = <0xff>;
>>          mode-rescue = <0xf9>;
>>          mode-shutdown-thermal = <0x51>;
>>          mode-shutdown-thermal-battery = <0x51>;
>>
>>      arm64/boot/dts/hisilicon/hi3660-hikey960.dts:
>>          mode-normal = <0x77665501>;
>>          mode-bootloader = <0x77665500>;
>>          mode-recovery = <0x77665502>;
>>
>>      arm64/boot/dts/hisilicon/hi6220-hikey.dts:
>>          mode-normal = <0x77665501>;
>>          mode-bootloader = <0x77665500>;
>>          mode-recovery = <0x77665502>;
>>
>>      arm64/boot/dts/rockchip/px30.dtsi:
>>          mode-bootloader = <BOOT_BL_DOWNLOAD>;
>>          mode-fastboot = <BOOT_FASTBOOT>;
>>          mode-loader = <BOOT_BL_DOWNLOAD>;
>>          mode-normal = <BOOT_NORMAL>;
>>          mode-recovery = <BOOT_RECOVERY>;
>>
>>      arm64/boot/dts/rockchip/rk3308.dtsi:
>>          mode-bootloader = <BOOT_BL_DOWNLOAD>;
>>          mode-loader = <BOOT_BL_DOWNLOAD>;
>>          mode-normal = <BOOT_NORMAL>;
>>          mode-recovery = <BOOT_RECOVERY>;
>>          mode-fastboot = <BOOT_FASTBOOT>;
>>
>>      arm64/boot/dts/rockchip/rk3566-lckfb-tspi.dts:
>>          mode-normal = <BOOT_NORMAL>;
>>          mode-loader = <BOOT_BL_DOWNLOAD>;
>>             mode-recovery = <BOOT_RECOVERY>;
>>             mode-bootloader = <BOOT_FASTBOOT>;
>>
>> Detailed list of commands being used by nvmem-reboot-mode:
>>      arm64/boot/dts/qcom/pmXXXX.dtsi:(multiple qcom DTs)
>>             mode-recovery = <0x01>;
>>             mode-bootloader = <0x02>;
>>
>> Previous discussions around SYSTEM_RESET2:
>> - https://lore.kernel.org/lkml/20230724223057.1208122-2-quic_eberman@quicinc.com/T/
>> - https://lore.kernel.org/all/4a679542-b48d-7e11-f33a-63535a5c68cb@quicinc.com/
>>
>> Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
>> Signed-off-by: Shivendra Pratap <shivendra.pratap@oss.qualcomm.com>
>
> On ARCH_BRCMSTB:
>
> Tested-by: Florian Fainelli <florian.fainelli@broadcom.com>
>
> For the sysfs bits, should not we be seeing "psci" instead of "reboot-mode" twice in this path:
>
> # cat /sys/class/reboot-mode/reboot-mode/reboot_modes
> powercycle
As per current patch, we create a class named - "reboot-mode".
/sys/class/reboot-mode

Then comes the DT node name of the registering driver.
/sys/class/reboot-mode/ /

Then the name of the sysfs which is set to "reboot_modes".

For case of vendor reset, psci is parent and node name is reboot-mode,
so its generalized to: /sys/class/reboot-mode/reboot-mode/reboot_modes
--

We can discuss, how to keep it generalized and get some other name
in sysfs. suggestions?

>
> ?