panic: Set watchdog panic reason if old watchdog panic

The watchdog panic info may be set in watchdog handler or during system
pre init after the watchdog reset. It depends on the chip
implementation. For cortex-m on Zephyr, the watchdog panic reason is
not set in the watchdog handler.

The current logic in system pre init only sets the watchdog panic reason
when the current reason is not a watchdog. This means only the first
watchdog is reported. Successive watchdogs are ignored because the panic
flags are never reset. The panic flags will only be reset if a
non-watchdog panic occurs or EC memory cleared (FW update or 0 battery).

This change checks if the current watchdog panic is old. This is
inferred by checking for the PANIC_DATA_FLAG_OLD_HOSTCMD flag, which is
set when the host reads the panic info.

BUG=b:273516527
BRANCH=Zephyer NPCX boards
TEST=Succesive watchdogs are correctly reported in elog
TEST=drivers.system unit test

Change-Id: I91ec1bf75a85ea7fed978895a262ff74e6ac16c7
Signed-off-by: Rob Barnes <robbarnes@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/4415329
Commit-Queue: Aaron Massey <aaronmassey@google.com>
Reviewed-by: Aaron Massey <aaronmassey@google.com>

2 files changed, 59 insertions, 1 deletions

diff --git a/common/system.c b/common/system.c
index f7bdd5d402..adb8c665c3 100644
--- a/common/system.c
+++ b/common/system.c
@@ -903,9 +903,17 @@ void system_common_pre_init(void)
 		uint32_t reason;
 		uint32_t info;
 		uint8_t exception;
+		struct panic_data *pdata;
 
 		panic_get_reason(&reason, &info, &exception);
-		if (reason != PANIC_SW_WATCHDOG)
+		pdata = panic_get_data();
+		/* The watchdog panic info may have already been initialized by
+		 * the watchdog handler, so only set it here if the panic reason
+		 * is not a watchdog or the panic info has already been read,
+		 * i.e. an old watchdog panic.
+		 */
+		if (reason != PANIC_SW_WATCHDOG || !pdata ||
+		    pdata->flags & PANIC_DATA_FLAG_OLD_HOSTCMD)
 			panic_set_reason(PANIC_SW_WATCHDOG, 0, 0);
 	}
 
diff --git a/zephyr/test/drivers/system/src/system.c b/zephyr/test/drivers/system/src/system.c
index 2bd8554994..051723f194 100644
--- a/zephyr/test/drivers/system/src/system.c
+++ b/zephyr/test/drivers/system/src/system.c
@@ -98,11 +98,61 @@ ZTEST(system, test_system_common_pre_init__watch_dog_panic)
 	uint32_t info;
 	uint8_t exception;
 
+	/* Watchdog reset should result in any existing panic data being
+	 * overwritten
+	 */
+	panic_set_reason(PANIC_SW_DIV_ZERO, 0x12, 0x34);
+
+	/* Clear all reset flags and set them arbitrarily */
+	system_set_reset_flags(EC_RESET_FLAG_WATCHDOG);
+	system_common_pre_init();
+	panic_get_reason(&reason, &info, &exception);
+	zassert_equal(reason, PANIC_SW_WATCHDOG);
+	zassert_equal(info, 0);
+	zassert_equal(exception, 0);
+}
+
+ZTEST(system, test_system_common_pre_init__watch_dog_panic_already_initialized)
+{
+	uint32_t reason;
+	uint32_t info;
+	uint8_t exception;
+
+	/* Watchdog reset should not overwrite panic info if already filled
+	 * in with watchdog panic info that HAS NOT been read by host
+	 */
+	panic_set_reason(PANIC_SW_WATCHDOG, 0x12, 0x34);
+
+	/* Clear all reset flags and set them arbitrarily */
+	system_set_reset_flags(EC_RESET_FLAG_WATCHDOG);
+	system_common_pre_init();
+	panic_get_reason(&reason, &info, &exception);
+	zassert_equal(reason, PANIC_SW_WATCHDOG);
+	zassert_equal(info, 0x12);
+	zassert_equal(exception, 0x34);
+}
+
+ZTEST(system, test_system_common_pre_init__watch_dog_panic_already_read)
+{
+	uint32_t reason;
+	uint32_t info;
+	uint8_t exception;
+	struct panic_data *pdata;
+
+	/* Watchdog reset should overwrite panic info if already filled
+	 * in with watchdog panic info that HAS been read by host
+	 */
+	panic_set_reason(PANIC_SW_WATCHDOG, 0x12, 0x34);
+	pdata = get_panic_data_write();
+	pdata->flags |= PANIC_DATA_FLAG_OLD_HOSTCMD;
+
 	/* Clear all reset flags and set them arbitrarily */
 	system_set_reset_flags(EC_RESET_FLAG_WATCHDOG);
 	system_common_pre_init();
 	panic_get_reason(&reason, &info, &exception);
 	zassert_equal(reason, PANIC_SW_WATCHDOG);
+	zassert_equal(info, 0);
+	zassert_equal(exception, 0);
 }
 
 ZTEST(system, test_system_encode_save_flags)