Re: [PATCH v21 04/13] firmware: psci: Introduce command-based with magic

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

Correction in commit subject - firmware: psci: Introduce command-based 
resets

On 27-04-2026 23:04, Shivendra Pratap wrote:
> PSCI currently supports only two resets - SYSTEM_RESET and SYSTEM_RESET2
> ARCH WARM reset. The reset patch is selected based on the Linux
> reboot_mode variable. The PSCI specification now includes SYSTEM_RESET2
> for vendor-specific resets but there's no mechanism to issue these
> through psci_sys_reset().
> 
> Add a command-based reset mechanism that allows external drivers to set
> the psci reset command via a exported psci_set_reset_cmd() function.
> 
> Define predefined reset_types - PSCI_RESET_TYPE_SYSTEM_RESET to map to
> SYSTEM_RESET, and PSCI_RESET_TYPE_SYSTEM_RESET2_ARCH_WARM to map to
> SYSTEM_RESET2 arch warm reset. Interpret zero cmd_reset_type, for
> predefined reset-command selection via cmd_cookie. For non-zero
> cmd_reset_type, check for valid vendor_reset_type and set the psci
> reset_command and cookie accordingly.
> 
> Disable PSCI command-based reset by default and treat invalid reset
> commands as no‑op. psci_sys_reset() follows its original flow based on
> reboot_mode until a reset command is explicitly set by
> psci_set_reset_cmd().  In the device reset flow, psci_set_reset_cmd() is
> called in reboot_notifier phase and the device reset happens in
> psci_sys_reset() which is called later in the restart_notifier phase. If
> a kernel panic occurs in between these two phases, the reboot should
> take its original flow based on the value of reboot_mode. Disable the
> command-based reset in such case.
> 
> Signed-off-by: Shivendra Pratap <shivendra.pratap@oss.qualcomm.com>
> ---
>   drivers/firmware/psci/psci.c | 75 ++++++++++++++++++++++++++++++++++++++++++--
>   include/linux/psci.h         | 19 +++++++++++
>   2 files changed, 92 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
> index 38ca190d4a22d6e7e0f06420e8478a2b0ec2fe6f..cb37c39e2b4b1d99f0080f6a5cd6c92a070beda8 100644
> --- a/drivers/firmware/psci/psci.c
> +++ b/drivers/firmware/psci/psci.c
> @@ -51,6 +51,16 @@ static int resident_cpu = -1;
>   struct psci_operations psci_ops;
>   static enum arm_smccc_conduit psci_conduit = SMCCC_CONDUIT_NONE;
>   
> +/*
> + * Encoded reset command:
> + * bits[63:32] = cookie
> + * bits[31:0]  = reset_type
> + */
> +static u64 reset_cmd;
> +
> +#define PSCI_RESET_TYPE(reset_cmd)	((u32)(reset_cmd))
> +#define PSCI_RESET_COOKIE(reset_cmd)	((u32)((reset_cmd) >> 32))
> +
>   bool psci_tos_resident_on(int cpu)
>   {
>   	return cpu == resident_cpu;
> @@ -80,6 +90,35 @@ static u32 psci_cpu_suspend_feature;
>   static bool psci_system_reset2_supported;
>   static bool psci_system_off2_hibernate_supported;
>   
> +static u32 psci_fn_from_cookie(u32 cookie)
> +{
> +	switch (cookie) {
> +	case PSCI_RESET_TYPE_SYSTEM_RESET2_ARCH_WARM:
> +		if (psci_system_reset2_supported)
> +			return PSCI_FN_NATIVE(1_1, SYSTEM_RESET2);
> +		return 0;
> +	case PSCI_RESET_TYPE_SYSTEM_RESET:
> +		return PSCI_0_2_FN_SYSTEM_RESET;
> +	default:
> +		return 0;
> +	}
> +}
> +
> +/** psci_set_reset_cmd() - Configure reset request for psci_sys_reset()
> + * @psci_reset_cmd: reset command encoded as cookie[63:32] | reset_type[31:0]
> + *
> + * Save reset command.
> + */
> +void psci_set_reset_cmd(u64 psci_reset_cmd)
> +{
> +	reset_cmd = psci_reset_cmd;
> +}
> +
> +bool psci_has_system_reset2_support(void)
> +{
> +	return psci_system_reset2_supported;
> +}
> +
>   static inline bool psci_has_ext_power_state(void)
>   {
>   	return psci_cpu_suspend_feature &
> @@ -306,8 +345,24 @@ static int get_set_conduit_method(const struct device_node *np)
>   	return 0;
>   }
>   
> -static int psci_sys_reset(struct notifier_block *nb, unsigned long action,
> -			  void *data)
> +static void psci_handle_reset_cmd(void)
> +{
> +	u32 psci_sys_reset_fn;
> +
> +	if ((reset_cmd & BIT_ULL(31)) && psci_system_reset2_supported) {
> +		/* PSCI SYSTEM_RESET2 Vendor-specific reset */
> +		invoke_psci_fn(PSCI_FN_NATIVE(1_1, SYSTEM_RESET2),
> +			       PSCI_RESET_TYPE(reset_cmd),
> +			       PSCI_RESET_COOKIE(reset_cmd), 0);
> +	} else {
> +		/* cookie part of the reset_cmd decides ARCH WARM RESET vs SYSTEM_RESET */
> +		psci_sys_reset_fn = psci_fn_from_cookie(PSCI_RESET_COOKIE(reset_cmd));
> +		if (!PSCI_RESET_TYPE(reset_cmd) && psci_sys_reset_fn)
> +			invoke_psci_fn(psci_sys_reset_fn, 0, 0, 0);
> +	}
> +}
> +
> +static void psci_handle_reboot_mode(void)
>   {
>   	if ((reboot_mode == REBOOT_WARM || reboot_mode == REBOOT_SOFT) &&
>   	    psci_system_reset2_supported) {
> @@ -320,6 +375,22 @@ static int psci_sys_reset(struct notifier_block *nb, unsigned long action,
>   	} else {
>   		invoke_psci_fn(PSCI_0_2_FN_SYSTEM_RESET, 0, 0, 0);
>   	}
> +}
> +
> +static int psci_sys_reset(struct notifier_block *nb, unsigned long action,
> +			  void *data)
> +{
> +	/*
> +	 * Command-based resets are configured at the reboot_notifier phase.
> +	 * If a kernel panic occurs between the reboot_notifier and this final
> +	 * reset, ignore the command-based reset and let reboot_mode drive the
> +	 * reset flow.
> +	 * If reset_cmd is zero, there is no command to handle.
> +	 */
> +	if (reset_cmd && !panic_in_progress())
> +		psci_handle_reset_cmd();
> +	else
> +		psci_handle_reboot_mode();
>   
>   	return NOTIFY_DONE;
>   }
> diff --git a/include/linux/psci.h b/include/linux/psci.h
> index 4ca0060a3fc42ba1ca751c7862fb4ad8dda35a4c..c2458291a3faf5ac89b1528dae2c9b805a2dd075 100644
> --- a/include/linux/psci.h
> +++ b/include/linux/psci.h
> @@ -21,6 +21,21 @@ bool psci_power_state_is_valid(u32 state);
>   int psci_set_osi_mode(bool enable);
>   bool psci_has_osi_support(void);
>   
> +/**
> + * enum psci_reset_type	-	PSCI_RESET_TYPE for SYSTEM_RESET.
> + * @PSCI_RESET_TYPE_SYSTEM_RESET: Standard SYSTEM_RESET command.
> + * @PSCI_RESET_TYPE_SYSTEM_RESET2_ARCH_WARM: SYSTEM_RESET2 architectural warm reset.
> + *
> + * These enum values map PSCI_RESET_TYPE_SYSTEM_* constants to reset strings
> + * issued from user space. When user space requests a reset, the cookie
> + * carries one of these values, and the PSCI reset path translates it into
> + * the appropriate PSCI system reset call.
> + */
> +enum psci_reset_type {
> +	PSCI_RESET_TYPE_SYSTEM_RESET = 1,
> +	PSCI_RESET_TYPE_SYSTEM_RESET2_ARCH_WARM,
> +};
> +
>   struct psci_operations {
>   	u32 (*get_version)(void);
>   	int (*cpu_suspend)(u32 state, unsigned long entry_point);
> @@ -45,8 +60,12 @@ struct psci_0_1_function_ids get_psci_0_1_function_ids(void);
>   
>   #if defined(CONFIG_ARM_PSCI_FW)
>   int __init psci_dt_init(void);
> +void psci_set_reset_cmd(u64 psci_reset_cmd);
> +bool psci_has_system_reset2_support(void);
>   #else
>   static inline int psci_dt_init(void) { return 0; }
> +static inline void psci_set_reset_cmd(u64 psci_reset_cmd) { }
> +static inline bool psci_has_system_reset2_support(void) { return false; }
>   #endif
>   
>   #if defined(CONFIG_ARM_PSCI_FW) && defined(CONFIG_ACPI)
>