mec1322: Refine reset cause detection

The VBAT POR indication is unreliable for detecting a power-on reset,
and thus we often see "unknown" reset cause when we should see
"power-on". A better indication is to check for VCC1 POR, which
manifests by clearing watchdog count. The catch is that we still cannot
tell power-on reset from reset-pin reset.

Also, to distinguish soft/hard reset from actual watchdog reset, we need
to explicitly save soft/hard reset flag before triggering watchdog
reset.

BUG=chrome-os-partner:24107
TEST=Power cycle EVB and see 'power-on' reset cause.
TEST='reboot' and see 'soft' reset cause.
TEST='reboot hard' and see 'hard' reset cause.
TEST='waitms 2000' and see 'watchdog' reset cause.
BRANCH=None

Change-Id: I0075f5bf5cdb032d206c4a53c586b75b69093235
Signed-off-by: Vic (Chun-Ju) Yang <victoryang@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/182120
Reviewed-by: Randall Spangler <rspangler@chromium.org>

2 files changed, 24 insertions, 4 deletions

diff --git a/chip/mec1322/registers.h b/chip/mec1322/registers.h
index 47a839ed96..edc276f0eb 100644
--- a/chip/mec1322/registers.h
+++ b/chip/mec1322/registers.h
@@ -43,6 +43,7 @@
 #define MEC1322_EC_INT_CTRL    REG32(MEC1322_EC_BASE + 0x18)
 #define MEC1322_EC_TRACE_EN    REG32(MEC1322_EC_BASE + 0x1c)
 #define MEC1322_EC_JTAG_EN     REG32(MEC1322_EC_BASE + 0x20)
+#define MEC1322_EC_WDT_CNT     REG32(MEC1322_EC_BASE + 0x28)
 
 
 /* Interrupt aggregator */
diff --git a/chip/mec1322/system.c b/chip/mec1322/system.c
index aa7b36e459..7364029498 100644
--- a/chip/mec1322/system.c
+++ b/chip/mec1322/system.c
@@ -22,6 +22,20 @@ enum hibdata_index {
 	HIBDATA_INDEX_SAVED_RESET_FLAGS  /* Saved reset flags */
 };
 
+static int check_vcc1_por(void)
+{
+	/*
+	 * WDT count resets on VCC1 POR. If we see WDT count = 0, we know
+	 * POR has occurred, and we set WDT count to 1.
+	 */
+	if (MEC1322_EC_WDT_CNT == 0) {
+		MEC1322_EC_WDT_CNT = 1;
+		return 1;
+	}
+
+	return 0;
+}
+
 static void check_reset_cause(void)
 {
 	uint32_t status = MEC1322_VBAT_STS;
@@ -30,15 +44,15 @@ static void check_reset_cause(void)
 	/* Clear the reset causes now that we've read them */
 	MEC1322_VBAT_STS |= status;
 
-	if (status & (1 << 7))
+	if (status & (1 << 7) || check_vcc1_por())
 		flags |= RESET_FLAG_POWER_ON;
 
-	if (status & (1 << 5))
-		flags |= RESET_FLAG_WATCHDOG;
-
 	flags |= MEC1322_VBAT_RAM(HIBDATA_INDEX_SAVED_RESET_FLAGS);
 	MEC1322_VBAT_RAM(HIBDATA_INDEX_SAVED_RESET_FLAGS) = 0;
 
+	if (status & (1 << 5) && !(flags & (RESET_FLAG_SOFT | RESET_FLAG_HARD)))
+		flags |= RESET_FLAG_WATCHDOG;
+
 	system_set_reset_flags(flags);
 }
 
@@ -70,6 +84,11 @@ void system_reset(int flags)
 	if (flags & SYSTEM_RESET_LEAVE_AP_OFF)
 		save_flags |= RESET_FLAG_AP_OFF;
 
+	if (flags & SYSTEM_RESET_HARD)
+		save_flags |= RESET_FLAG_HARD;
+	else
+		save_flags |= RESET_FLAG_SOFT;
+
 	MEC1322_VBAT_RAM(HIBDATA_INDEX_SAVED_RESET_FLAGS) = save_flags;
 
 	/* Trigger watchdog in 1ms */