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

[Shivendra Pratap <shivendra.pratap@oss.qualcomm.com>]

On 9/30/2025 11:15 AM, Kathiravan Thirumoorthy wrote:
> 
> 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(-)
>>
>> diff --git a/drivers/firmware/psci/Kconfig b/drivers/firmware/psci/Kconfig
>> index 97944168b5e66aea1e38a7eb2d4ced8348fce64b..93ff7b071a0c364a376699733e6bc5654d56a17f 100644
>> --- a/drivers/firmware/psci/Kconfig
>> +++ b/drivers/firmware/psci/Kconfig
>> @@ -1,6 +1,8 @@
>>   # SPDX-License-Identifier: GPL-2.0-only
>>   config ARM_PSCI_FW
>>       bool
>> +    select POWER_RESET
>> +    select REBOOT_MODE
>>     config ARM_PSCI_CHECKER
>>       bool "ARM PSCI checker"
>> diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
>> index 38ca190d4a22d6e7e0f06420e8478a2b0ec2fe6f..40a27bc2cc3a3393acc14c7b2314155540ed06c9 100644
>> --- a/drivers/firmware/psci/psci.c
>> +++ b/drivers/firmware/psci/psci.c
>> @@ -13,10 +13,12 @@
>>   #include <linux/errno.h>
>>   #include <linux/linkage.h>
>>   #include <linux/of.h>
>> +#include <linux/panic_notifier.h>
>>   #include <linux/pm.h>
>>   #include <linux/printk.h>
>>   #include <linux/psci.h>
>>   #include <linux/reboot.h>
>> +#include <linux/reboot-mode.h>
>>   #include <linux/slab.h>
>>   #include <linux/suspend.h>
>>   @@ -51,6 +53,24 @@ static int resident_cpu = -1;
>>   struct psci_operations psci_ops;
>>   static enum arm_smccc_conduit psci_conduit = SMCCC_CONDUIT_NONE;
>>   +struct psci_vendor_sysreset2 {
>> +    u32 reset_type;
>> +    u32 cookie;
>> +    bool valid;
>> +};
>> +
>> +static struct psci_vendor_sysreset2 vendor_reset;
>> +
>> +static int psci_panic_event(struct notifier_block *nb, unsigned long v, void *p)
>> +{
>> +    vendor_reset.valid = false;
>> +    return NOTIFY_DONE;
>> +}
>> +
>> +static struct notifier_block psci_panic_block = {
>> +    .notifier_call = psci_panic_event
>> +};
>> +
>>   bool psci_tos_resident_on(int cpu)
>>   {
>>       return cpu == resident_cpu;
>> @@ -309,7 +329,10 @@ static int get_set_conduit_method(const struct device_node *np)
>>   static int psci_sys_reset(struct notifier_block *nb, unsigned long action,
>>                 void *data)
>>   {
>> -    if ((reboot_mode == REBOOT_WARM || reboot_mode == REBOOT_SOFT) &&
>> +    if (vendor_reset.valid && psci_system_reset2_supported) {
>> +        invoke_psci_fn(PSCI_FN_NATIVE(1_1, SYSTEM_RESET2), vendor_reset.reset_type,
>> +                   vendor_reset.cookie, 0);
>> +    } else if ((reboot_mode == REBOOT_WARM || reboot_mode == REBOOT_SOFT) &&
>>           psci_system_reset2_supported) {
>>           /*
>>            * reset_type[31] = 0 (architectural)
>> @@ -547,6 +570,70 @@ static const struct platform_suspend_ops psci_suspend_ops = {
>>       .enter          = psci_system_suspend_enter,
>>   };
>>   +static int psci_set_vendor_sys_reset2(struct reboot_mode_driver *reboot, u64 magic)
>> +{
>> +    u32 magic_32;
>> +
>> +    if (psci_system_reset2_supported) {
>> +        magic_32 = magic & 0xffffffff;
>> +        vendor_reset.reset_type = PSCI_1_1_RESET_TYPE_VENDOR_START | magic_32;
>> +        vendor_reset.cookie = (magic >> 32) & 0xffffffff;
> 
> 
> Minor Nit: Can we use GENMASK(31, 0) instead of 0xffffffff? Apart from this, change LGTM. With that,

Ack. Will update this.

> 
> Reviewed-by: Kathiravan Thirumoorthy <kathiravan.thirumoorthy@oss.qualcomm.com>

thanks for review.

thanks,
Shivendra