[PATCH v3 1/3] power: reset: pscrr: add kernel panic reason tracking

[Faruque Ansari]

Kernel panic resets are not recorded in NVMEM, causing subsequent
boots to report PSCR_UNKNOWN and making post-mortem analysis more
difficult.

Register a panic notifier to preserve the shutdown reason across
panic-triggered resets. Add PSCR_KERNEL_PANIC as a dedicated reset
reason code and its corresponding reason string to identify kernel
panic resets on subsequent boots.

Signed-off-by: Faruque Ansari <faruque.ansari@xxxxxxxxxxxxxxxx>
---
 drivers/power/reset/pscrr/pscrr.c     | 27 +++++++++++++++++++++++++++
 include/linux/power/power_on_reason.h |  1 +
 include/linux/reboot.h                |  3 +++
 kernel/reboot.c                       |  1 +
 4 files changed, 32 insertions(+)

diff --git a/drivers/power/reset/pscrr/pscrr.c b/drivers/power/reset/pscrr/pscrr.c
index 6f23f4c4f590..8c45b84059a9 100644
--- a/drivers/power/reset/pscrr/pscrr.c
+++ b/drivers/power/reset/pscrr/pscrr.c
@@ -41,6 +41,7 @@
 #include <linux/mutex.h>
 #include <linux/notifier.h>
 #include <linux/of.h>
+#include <linux/panic_notifier.h>
 #include <linux/pscrr.h>
 #include <linux/reboot.h>
 #include <linux/slab.h>
@@ -519,6 +520,29 @@ static struct notifier_block pscrr_reboot_nb = {
 	.notifier_call = pscrr_reboot_notifier,
 };
 
+/*
+ * Panic notifier: record that the machine went down through a kernel panic, so
+ * the cause is visible on the next boot. Runs in atomic panic context, so the
+ * provider list is walked without pscrr_lock - providers no longer come or go
+ * once the machine is going down.
+ */
+static int pscrr_panic_notifier(struct notifier_block *nb,
+				unsigned long action, void *unused)
+{
+	struct pscrr_provider_dir *dir;
+
+	set_psc_reason(PSCR_KERNEL_PANIC);
+
+	list_for_each_entry(dir, &pscrr_dirs, node)
+		pscrr_do_record(dir, get_psc_reason());
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block pscrr_panic_nb = {
+	.notifier_call = pscrr_panic_notifier,
+};
+
 /*----------------------------------------------------------------------*/
 /* Built-in provider: device-tree /chosen/reset-source                  */
 /*----------------------------------------------------------------------*/
@@ -611,6 +635,8 @@ static int __init pscrr_core_init(void)
 		return ret;
 	}
 
+	atomic_notifier_chain_register(&panic_notifier_list, &pscrr_panic_nb);
+
 	pscrr_register_reset_source();
 
 	return 0;
@@ -619,6 +645,7 @@ static int __init pscrr_core_init(void)
 static void __exit pscrr_core_exit(void)
 {
 	pscrr_provider_unregister(&pscrr_reset_source_provider);
+	atomic_notifier_chain_unregister(&panic_notifier_list, &pscrr_panic_nb);
 	unregister_reboot_notifier(&pscrr_reboot_nb);
 	kobject_put(pscrr_root);
 	pscrr_root = NULL;
diff --git a/include/linux/power/power_on_reason.h b/include/linux/power/power_on_reason.h
index 13e61ace14f5..8c99bdd75021 100644
--- a/include/linux/power/power_on_reason.h
+++ b/include/linux/power/power_on_reason.h
@@ -20,5 +20,6 @@
 #define POWER_ON_REASON_OVER_TEMPERATURE "over temperature"
 #define POWER_ON_REASON_EC_PANIC "EC panic"
 #define POWER_ON_REASON_EXTERNAL "external reset"
+#define POWER_ON_REASON_KERNEL_PANIC "kernel panic"
 
 #endif /* POWER_ON_REASON_H */
diff --git a/include/linux/reboot.h b/include/linux/reboot.h
index 13f004ad1066..a117dd5eaecd 100644
--- a/include/linux/reboot.h
+++ b/include/linux/reboot.h
@@ -241,6 +241,8 @@ extern void orderly_reboot(void);
  *
  * @PSCR_XTAL_FAIL: Reset caused by a crystal oscillator failure.
  *
+ * @PSCR_KERNEL_PANIC: Reset that followed a kernel panic.
+ *
  * @PSCR_REASON_COUNT: Number of defined power state change reasons. This
  *	value is useful for range checking and potential future extensions
  *	while maintaining compatibility.
@@ -264,6 +266,7 @@ enum psc_reason {
 	PSCR_RESET_BUTTON,
 	PSCR_CPU_CLK_FAIL,
 	PSCR_XTAL_FAIL,
+	PSCR_KERNEL_PANIC,
 
 	/* Number of reasons */
 	PSCR_REASON_COUNT,
diff --git a/kernel/reboot.c b/kernel/reboot.c
index 75af5d763465..979ecf3b093c 100644
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -1109,6 +1109,7 @@ static const struct psc_reason_desc psc_reason_descs[] = {
 	[PSCR_RESET_BUTTON]	 = { "reset-button",	  POWER_ON_REASON_RST_BTN },
 	[PSCR_CPU_CLK_FAIL]	 = { "cpu-clock-failure", POWER_ON_REASON_CPU_CLK_FAIL },
 	[PSCR_XTAL_FAIL]	 = { "crystal-failure",	  POWER_ON_REASON_XTAL_FAIL },
+	[PSCR_KERNEL_PANIC]	 = { "kernel-panic",	  POWER_ON_REASON_KERNEL_PANIC },
 };
 
 /**

-- 
2.34.1