Index: sys/dev/iicbus/twsi/twsi.c
===================================================================
--- sys/dev/iicbus/twsi/twsi.c
+++ sys/dev/iicbus/twsi/twsi.c
@@ -481,12 +481,17 @@
 twsi_transfer(device_t dev, struct iic_msg *msgs, uint32_t nmsgs)
 {
 	struct twsi_softc *sc;
+	int i;
 
 	sc = device_get_softc(dev);
 
 	if (sc->have_intr == false)
 		return (iicbus_transfer_gen(dev, msgs, nmsgs));
 
+	sc->nmsgs = nmsgs;
+	sc->msgs = msgs;
+	sc->msg_idx = 0;
+	sc->transfer = 1;
 	sc->error = 0;
 
 	sc->control_val = TWSI_CONTROL_TWSIEN |
@@ -494,10 +499,6 @@
 	TWSI_WRITE(sc, sc->reg_control, sc->control_val);
 	debugf(dev, "transmitting %d messages\n", nmsgs);
 	debugf(sc->dev, "status=%x\n", TWSI_READ(sc, sc->reg_status));
-	sc->nmsgs = nmsgs;
-	sc->msgs = msgs;
-	sc->msg_idx = 0;
-	sc->transfer = 1;
 
 #ifdef TWSI_DEBUG
 	for (int i = 0; i < nmsgs; i++)
@@ -506,12 +507,15 @@
 	/* Send start and re-enable interrupts */
 	sc->control_val = TWSI_CONTROL_TWSIEN |
 		TWSI_CONTROL_INTEN | TWSI_CONTROL_ACK;
-	if (sc->msgs[0].len == 1)
-		sc->control_val &= ~TWSI_CONTROL_ACK;
 	TWSI_WRITE(sc, sc->reg_control, sc->control_val | TWSI_CONTROL_START);
-	while (sc->error == 0 && sc->transfer != 0) {
+	for (i = 0; i < 100 && sc->error == 0 && sc->transfer != 0; i++) {
 		pause_sbt("twsi", SBT_1MS * 30, SBT_1MS, 0);
 	}
+	if (sc->error == 0 && sc->transfer != 0) {
+		device_printf(sc->dev, "transfer timeout\n");
+		sc->error = IIC_ETIMEOUT;
+		sc->transfer = 0;
+	}
 	debugf(sc->dev, "pause finish\n");
 
 	if (sc->error) {
@@ -533,6 +537,7 @@
 	struct twsi_softc *sc;
 	uint32_t status;
 	int transfer_done = 0;
+	int send_byte = 0;
 
 	sc = arg;
 
@@ -541,6 +546,9 @@
 	status = TWSI_READ(sc, sc->reg_status);
 	debugf(sc->dev, "reg control=%x\n", TWSI_READ(sc, sc->reg_control));
 
+	if (sc->transfer == 0)
+		device_printf(sc->dev, "interrupt without active transfer\n");
+
 	switch (status) {
 	case TWSI_STATUS_START:
 	case TWSI_STATUS_RPTD_START:
@@ -572,6 +580,8 @@
 		debugf(sc->dev, "Ack received after transmitting the address (read)\n");
 		sc->recv_bytes = 0;
 
+		if (sc->msgs[sc->msg_idx].len == 1)
+			sc->control_val &= ~TWSI_CONTROL_ACK;
 		TWSI_WRITE(sc, sc->reg_control, sc->control_val);
 		break;
 
@@ -579,7 +589,7 @@
 	case TWSI_STATUS_ADDR_R_NACK:
 		debugf(sc->dev, "No ack received after transmitting the address\n");
 		sc->transfer = 0;
-		sc->error = ETIMEDOUT;
+		sc->error = IIC_ENOACK;
 		sc->control_val = 0;
 		wakeup(sc);
 		break;
@@ -588,6 +598,8 @@
 		debugf(sc->dev, "Ack received after transmitting data\n");
 		if (sc->sent_bytes == sc->msgs[sc->msg_idx].len) {
 			debugf(sc->dev, "Done sending all the bytes for msg %d\n", sc->msg_idx);
+			send_byte = 0;
+
 			/* Send stop, no interrupts on stop */
 			if (!(sc->msgs[sc->msg_idx].flags & IIC_M_NOSTOP)) {
 				debugf(sc->dev, "Done TX data, send stop\n");
@@ -595,18 +607,29 @@
 				    sc->control_val | TWSI_CONTROL_STOP);
 			} else {
 				debugf(sc->dev, "Done TX data with NO_STOP\n");
-				TWSI_WRITE(sc, sc->reg_control, sc->control_val | TWSI_CONTROL_START);
+				//TWSI_WRITE(sc, sc->reg_control, sc->control_val | TWSI_CONTROL_START);
 			}
 			sc->msg_idx++;
 			if (sc->msg_idx == sc->nmsgs) {
 				debugf(sc->dev, "transfer_done=1\n");
 				transfer_done = 1;
 				sc->error = 0;
-			} else {
+			} else if (!(sc->msgs[sc->msg_idx].flags & IIC_M_NOSTART)) {
 				debugf(sc->dev, "Send repeated start\n");
 				TWSI_WRITE(sc, sc->reg_control, sc->control_val | TWSI_CONTROL_START);
+			} else {
+				/* Just keep sending data. */
+				KASSERT((sc->msgs[sc->msg_idx].flags & IIC_M_RD) == 0,
+				    ("read with nostart after write with nostop"));
+				debugf(sc->dev, "write followed by write\n");
+				sc->sent_bytes = 0;
+				send_byte = 1;
 			}
 		} else {
+			send_byte = 1;
+		}
+
+		if (send_byte) {
 			debugf(sc->dev, "Sending byte %d (of %d) = %x\n",
 			    sc->sent_bytes,
 			    sc->msgs[sc->msg_idx].len,
@@ -660,7 +683,7 @@
 	default:
 		debugf(sc->dev, "status=%x hot handled\n", status);
 		sc->transfer = 0;
-		sc->error = ENXIO;
+		sc->error = IIC_EBUSERR;
 		sc->control_val = 0;
 		wakeup(sc);
 		break;