driver: Add timestamp read-out function.

Implemented protection against overflow between read from
TIMESTAMP_LOW and TIMESTAMP_HIGH word.

driver/ctu_can_fd_hw.c

@@ -774,4 +774,21 @@ bool ctu_can_fd_insert_frame(struct ctucanfd_priv *priv,
 	return true;
 }
 
+static u64 ctu_can_fd_read_timestamp(struct ctucanfd_priv *priv)
+{
+	union ctu_can_fd_timestamp_low ts_low;
+	union ctu_can_fd_timestamp_high ts_high;
+	union ctu_can_fd_timestamp_high ts_high_2;
+
+    ts_high.u32 = priv->read_reg(priv, CTU_CAN_FD_TIMESTAMP_HIGH);	
+    ts_low.u32 = priv->read_reg(priv, CTU_CAN_FD_TIMESTAMP_LOW);
+	ts_high_2.u32 = priv->read_reg(priv, CTU_CAN_FD_TIMESTAMP_HIGH);
+
+	if (ts_high.u32 != ts_high_2.u32){
+		ts_low.u32 = priv->read_reg(priv, CTU_CAN_FD_TIMESTAMP_LOW);
+	}
+
+	return (( (u64) ts_high_2.u32) << 32) | ( (u64) ts_low.u32);
+}
+
 // TODO: AL_CAPTURE and ERROR_CAPTURE

driver/ctu_can_fd_hw.h

@@ -955,6 +955,20 @@ static inline union ctu_can_fd_debug_register
 	return reg;
 }
 
+
+/*
+ * Read timestamp value which is used internally by CTU CAN FD Core.
+ * Reads timestamp twice and checks consistency betwen upper and
+ * lower timestamp word.
+ *
+ * Arguments:
+ *	priv	Private info
+ * Returns:
+ *	Value of timestamp in CTU CAN FD Core
+ */
+static u64 ctu_can_fd_read_timestamp(struct ctucanfd_priv *priv);
+
+
 extern const struct can_bittiming_const ctu_can_fd_bit_timing_max;
 extern const struct can_bittiming_const ctu_can_fd_bit_timing_data_max;