[PATCH v23 04/13] firmware: psci: Introduce command-based resets
Shivendra Pratap
shivendra.pratap at oss.qualcomm.com
Tue Jul 14 10:16:32 PDT 2026
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 by passing a reset_type and a cookie.
Add support for the following reset commands:
- SYSTEM_RESET2 vendor-specific resets.
- SYSTEM_RESET2 ARCH WARM reset and SYSTEM_RESET (reset_type = 0 and
cookie maps to psci_standard_resets).
Unsupported commands fall back to the regular PSCI reset path.
Default to the existing reboot_mode-based reset flow unless a reset
command is configured. If a kernel panic occurs after a reset command is
set but before the final PSCI reset is issued, ignore the reset command
and follow the normal reboot_mode-based reset path.
Signed-off-by: Shivendra Pratap <shivendra.pratap at oss.qualcomm.com>
---
drivers/firmware/psci/psci.c | 106 ++++++++++++++++++++++++++++++++++++++++++-
include/linux/psci.h | 36 +++++++++++++++
2 files changed, 140 insertions(+), 2 deletions(-)
diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
index e73bae6cb23a..881819d09911 100644
--- a/drivers/firmware/psci/psci.c
+++ b/drivers/firmware/psci/psci.c
@@ -12,7 +12,9 @@
#include <linux/debugfs.h>
#include <linux/errno.h>
#include <linux/linkage.h>
+#include <linux/mutex.h>
#include <linux/of.h>
+#include <linux/panic.h>
#include <linux/pm.h>
#include <linux/printk.h>
#include <linux/psci.h>
@@ -51,6 +53,14 @@ static int resident_cpu = -1;
struct psci_operations psci_ops;
static enum arm_smccc_conduit psci_conduit = SMCCC_CONDUIT_NONE;
+struct psci_system_reset_cmd {
+ u32 reset_type;
+ u64 cookie;
+};
+
+static struct psci_system_reset_cmd reset_cmd;
+static DEFINE_MUTEX(reset_cmd_mutex);
+
bool psci_tos_resident_on(int cpu)
{
return cpu == resident_cpu;
@@ -80,6 +90,62 @@ static u32 psci_cpu_suspend_feature;
static bool psci_system_reset2_supported;
static bool psci_system_off2_hibernate_supported;
+static u32 psci_get_sys_reset_fn(void)
+{
+ switch (reset_cmd.cookie) {
+ case PSCI_SYSTEM_RESET2_ARCH_WARM_RESET:
+ if (psci_system_reset2_supported)
+ return PSCI_FN_NATIVE(1_1, SYSTEM_RESET2);
+ return 0;
+ case PSCI_SYSTEM_RESET_COLD_RESET:
+ return PSCI_0_2_FN_SYSTEM_RESET;
+ default:
+ return 0;
+ }
+}
+
+/** psci_set_reset_cmd() - Configure PSCI reset command
+ * @reset_type: SYSTEM_RESET2 vendor-specific reset_type as defined by
+ * firmware, or 0 for standard resets
+ * @cookie: SYSTEM_RESET2 vendor-specific cookie as defined by firmware or one
+ * of enum psci_standard_resets when @reset_type is set to 0
+ *
+ * Supported commands:
+ * - PSCI SYSTEM_RESET2 vendor-specific reset:
+ * - @reset_type and @cookie must follow platform-specific SYSTEM_RESET2
+ * vendor-specific resets.
+ * - Standard reset selector:
+ * - @reset_type must be 0.
+ * - @cookie must be one of enum psci_standard_resets.
+ *
+ * This is an in-kernel helper intended for built-in reboot flow callers.
+ * reset command can be set only one time per boot cycle.
+ *
+ * Return: 0 on success, -EINVAL if both inputs are zero, -EBUSY if reset
+ * command is already set.
+ */
+int psci_set_reset_cmd(u32 reset_type, u64 cookie)
+{
+ if (!reset_type && !cookie)
+ return -EINVAL;
+
+ scoped_guard(mutex, &reset_cmd_mutex) {
+ if (reset_cmd.reset_type || reset_cmd.cookie)
+ return -EBUSY;
+
+ reset_cmd.reset_type = reset_type;
+ reset_cmd.cookie = cookie;
+ }
+
+ return 0;
+}
+
+bool psci_has_system_reset2_support(void)
+{
+ return psci_system_reset2_supported;
+}
+EXPORT_SYMBOL_GPL(psci_has_system_reset2_support);
+
static inline bool psci_has_ext_power_state(void)
{
return psci_cpu_suspend_feature &
@@ -306,8 +372,24 @@ 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.reset_type & PSCI_1_1_RESET_TYPE_VENDOR_START) &&
+ psci_system_reset2_supported) {
+ /* PSCI SYSTEM_RESET2 Vendor-specific reset */
+ invoke_psci_fn(PSCI_FN_NATIVE(1_1, SYSTEM_RESET2),
+ reset_cmd.reset_type, reset_cmd.cookie, 0);
+ } else {
+ /* Retrieve the psci reset function from reset_cmd */
+ psci_sys_reset_fn = psci_get_sys_reset_fn();
+ if (!reset_cmd.reset_type && 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 +402,26 @@ 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)
+{
+ /* The function psci_handle_reboot_mode follows reboot_mode based
+ * reset flow and psci_handle_reset_cmd uses reset_cmd based reset flow.
+ *
+ * The reset_cmd is configured at the reboot_notifier phase. If a kernel
+ * panic occurs between the reboot_notifier and this final reset, skip the
+ * command-based reset and let reboot_mode drive the reset flow.
+ *
+ * The function psci_handle_reset_cmd invokes non-returning PSCI SYSTEM_RESET
+ * calls to reset the device. If it returns, either the reset failed, or the
+ * command was unsupported. Fallback to reboot_mode based reset flow.
+ */
+ if ((reset_cmd.reset_type || reset_cmd.cookie) && !panic_in_progress())
+ psci_handle_reset_cmd();
+
+ psci_handle_reboot_mode();
return NOTIFY_DONE;
}
diff --git a/include/linux/psci.h b/include/linux/psci.h
index 4ca0060a3fc4..39fe0edec651 100644
--- a/include/linux/psci.h
+++ b/include/linux/psci.h
@@ -8,6 +8,7 @@
#define __LINUX_PSCI_H
#include <linux/arm-smccc.h>
+#include <linux/errno.h>
#include <linux/init.h>
#include <linux/types.h>
@@ -21,6 +22,16 @@ bool psci_power_state_is_valid(u32 state);
int psci_set_osi_mode(bool enable);
bool psci_has_osi_support(void);
+/**
+ * enum psci_standard_resets - Standard reset selectors for PSCI reset
+ * @PSCI_SYSTEM_RESET_COLD_RESET: Standard SYSTEM_RESET command.
+ * @PSCI_SYSTEM_RESET2_ARCH_WARM_RESET: SYSTEM_RESET2 architectural warm reset.
+ */
+enum psci_standard_resets {
+ PSCI_SYSTEM_RESET_COLD_RESET = 1,
+ PSCI_SYSTEM_RESET2_ARCH_WARM_RESET,
+};
+
struct psci_operations {
u32 (*get_version)(void);
int (*cpu_suspend)(u32 state, unsigned long entry_point);
@@ -45,8 +56,33 @@ 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);
+/**
+ * psci_set_reset_cmd() - Configure PSCI reset command
+ * @reset_type: SYSTEM_RESET2 vendor-specific reset_type as defined by
+ * firmware, or 0 for standard resets
+ * @cookie: SYSTEM_RESET2 vendor-specific cookie as defined by firmware or one
+ * of enum psci_standard_resets when @reset_type is set to 0
+ *
+ * Supported commands:
+ * - PSCI SYSTEM_RESET2 vendor-specific reset:
+ * - @reset_type and @cookie must follow platform-specific SYSTEM_RESET2
+ * vendor-reset encoding.
+ * - Standard reset selector:
+ * - @reset_type must be 0.
+ * - @cookie must be one of enum psci_standard_resets.
+ *
+ * This is an in-kernel helper intended for built-in reboot flow callers.
+ * reset command can be set only one time per boot cycle.
+ *
+ * Return: 0 on success, -EINVAL if both inputs are zero, -EBUSY if reset
+ * command is already set.
+ */
+int psci_set_reset_cmd(u32 reset_type, u64 cookie);
+bool psci_has_system_reset2_support(void);
#else
static inline int psci_dt_init(void) { return 0; }
+static inline int psci_set_reset_cmd(u32 reset_type, u64 cookie) { return 0; }
+static inline bool psci_has_system_reset2_support(void) { return false; }
#endif
#if defined(CONFIG_ARM_PSCI_FW) && defined(CONFIG_ACPI)
--
2.34.1
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