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

Shivendra Pratap
2026-04-27T17:36:06Z

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)

--
2.34.1