[PATCH v3 0/3] power: reset: pscrr: record reset cause on panic and watchdog pretimeout

[PATCH v3 0/3] power: reset: pscrr: record reset cause on panic and watchdog pretimeout

[Faruque Ansari]

This series extends the Power State Change Reason Register (PSCRR) [1]
framework to capture two additional reset causes.

  1. Kernel panic — a panic notifier writes PSCR_KERNEL_PANIC to NVMEM
     before the system resets, so the next boot can distinguish a panic
     from other reset causes.

  2. Watchdog pretimeout — set_psc_reason(PSCR_WATCHDOG_PRETIMEOUT) is
     called from pretimeout_panic(), when the watchdog fire its
     pre-reset notification before resetting the system, so the reason gets
     saved and we know its was a watchdog timeout that caused the reset.

[1] https://lore.kernel.org/all/20260731095959.296056-1-o.rempel@pengutronix.de/

Changes in v3:
  - Update patch 3/3 based on Guenter Roeck's feedback:
      * Move set_psc_reason(PSCR_WATCHDOG_PRETIMEOUT) from
        watchdog_notify_pretimeout() to pretimeout_panic().

Changes in v2:
https://lore.kernel.org/lkml/20260722-pscrr-reboot-reason-v2-0-495ba3005953@oss.qualcomm.com/
  - Split patch 2/2 into two patches as requested by Guenter Roeck:
      * Patch 2/3: power/reset — add PSCR_WATCHDOG_PRETIMEOUT and guard
          panic notifier against overwriting watchdog reason.
      * Patch 3/3: watchdog — hook set_psc_reason() into
          watchdog_notify_pretimeout().

Signed-off-by: Faruque Ansari <faruque.ansari@oss.qualcomm.com>
---
Faruque Ansari (3):
      power: reset: pscrr: add kernel panic reason tracking
      power: reset: pscrr: add watchdog pretimeout reason tracking
      watchdog: pretimeout: update PSC reason in panic pretimeout governor

 drivers/power/reset/pscrr/pscrr.c     | 30 ++++++++++++++++++++++++++++++
 drivers/watchdog/pretimeout_panic.c   |  2 ++
 include/linux/power/power_on_reason.h |  1 +
 include/linux/reboot.h                |  3 +++
 kernel/reboot.c                       |  1 +
 5 files changed, 37 insertions(+)
---
base-commit: 551961df5728932d968a4aae534714acfa43f3a1
change-id: 20260803-pscrr-reboot-reason-f1254965ec0d

Best regards,
-- 
Faruque Ansari <faruque.ansari@oss.qualcomm.com>

[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@oss.qualcomm.com>
---
 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

[PATCH v3 2/3] power: reset: pscrr: add watchdog pretimeout reason tracking

[Faruque Ansari]

Watchdog pretimeout resets are not recorded with a dedicated reason,
causing subsequent boots to report PSCR_UNKNOWN and making it difficult
to distinguish them from other unexpected resets.

Add PSCR_WATCHDOG_PRETIMEOUT as a dedicated reason code and prevent the
panic notifier from overwriting a watchdog pretimeout reason with
PSCR_KERNEL_PANIC when the pretimeout governor triggers a panic.

Signed-off-by: Faruque Ansari <faruque.ansari@oss.qualcomm.com>
---
 drivers/power/reset/pscrr/pscrr.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/power/reset/pscrr/pscrr.c b/drivers/power/reset/pscrr/pscrr.c
index 8c45b84059a9..b7e6239e207e 100644
--- a/drivers/power/reset/pscrr/pscrr.c
+++ b/drivers/power/reset/pscrr/pscrr.c
@@ -529,12 +529,15 @@ static struct notifier_block pscrr_reboot_nb = {
 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);
+	/*
+	 * Do not overwrite a watchdog pretimeout reason already set by the
+	 * pretimeout path before it triggered this panic.
+	 */
+	if (get_psc_reason() != PSCR_WATCHDOG_PRETIMEOUT)
+		set_psc_reason(PSCR_KERNEL_PANIC);
 
-	list_for_each_entry(dir, &pscrr_dirs, node)
-		pscrr_do_record(dir, get_psc_reason());
+	pscrr_record_current();
 
 	return NOTIFY_DONE;
 }

-- 
2.34.1

[PATCH v3 3/3] watchdog: pretimeout: update PSC reason in panic pretimeout governor

[Faruque Ansari]

Update the PSC reset reason by invoking
set_psc_reason(PSCR_WATCHDOG_PRETIMEOUT) from the panic governor's
pretimeout handler before calling panic(), so the reset cause is
committed to persistent storage before the system goes down.

Signed-off-by: Faruque Ansari <faruque.ansari@oss.qualcomm.com>
---
 drivers/watchdog/pretimeout_panic.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/watchdog/pretimeout_panic.c b/drivers/watchdog/pretimeout_panic.c
index 8c3ac674dc45..819487b5e6fe 100644
--- a/drivers/watchdog/pretimeout_panic.c
+++ b/drivers/watchdog/pretimeout_panic.c
@@ -5,6 +5,7 @@
 
 #include <linux/kernel.h>
 #include <linux/module.h>
+#include <linux/reboot.h>
 #include <linux/watchdog.h>
 
 #include "watchdog_pretimeout.h"
@@ -17,6 +18,7 @@
  */
 static void pretimeout_panic(struct watchdog_device *wdd)
 {
+	set_psc_reason(PSCR_WATCHDOG_PRETIMEOUT);
 	panic("watchdog pretimeout event\n");
 }
 

-- 
2.34.1

Re: [PATCH v3 3/3] watchdog: pretimeout: update PSC reason in panic pretimeout governor

[Guenter Roeck]

On 8/4/26 02:21, Faruque Ansari wrote:
> Update the PSC reset reason by invoking
> set_psc_reason(PSCR_WATCHDOG_PRETIMEOUT) from the panic governor's
> pretimeout handler before calling panic(), so the reset cause is
> committed to persistent storage before the system goes down.
> 
> Signed-off-by: Faruque Ansari <faruque.ansari@oss.qualcomm.com>

Acked-by: Guenter Roeck <linux@roeck-us.net>

> ---
>   drivers/watchdog/pretimeout_panic.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/watchdog/pretimeout_panic.c b/drivers/watchdog/pretimeout_panic.c
> index 8c3ac674dc45..819487b5e6fe 100644
> --- a/drivers/watchdog/pretimeout_panic.c
> +++ b/drivers/watchdog/pretimeout_panic.c
> @@ -5,6 +5,7 @@
>   
>   #include <linux/kernel.h>
>   #include <linux/module.h>
> +#include <linux/reboot.h>
>   #include <linux/watchdog.h>
>   
>   #include "watchdog_pretimeout.h"
> @@ -17,6 +18,7 @@
>    */
>   static void pretimeout_panic(struct watchdog_device *wdd)
>   {
> +	set_psc_reason(PSCR_WATCHDOG_PRETIMEOUT);
>   	panic("watchdog pretimeout event\n");
>   }
>   
>