drivers: i3c: mcux: tighten the FIFO read

At high i3c rates, the mcux_i3c_do_one_xfer_read()
could get into an infinite loop where the rx_count
kept returning 0 but the complete status bit
was never set. I believe the problem was that
the function was not emptying the FIFO fast enough,
so tighten the loop that processes the FIFO.

Signed-off-by: Mike J. Chen <[email protected]>

drivers/i3c/i3c_mcux.c

@@ -879,9 +879,7 @@ static int mcux_i3c_recover_bus(const struct device *dev)
  */
 static int mcux_i3c_do_one_xfer_read(I3C_Type *base, uint8_t *buf, uint8_t buf_sz)
 {
-	int rx_count;
 	bool completed = false;
-	bool overflow = false;
 	int ret = 0;
 	int offset = 0;
 
@@ -908,28 +906,19 @@ static int mcux_i3c_do_one_xfer_read(I3C_Type *base, uint8_t *buf, uint8_t buf_s
 		}
 
 		/*
-		 * Transfer data from FIFO into buffer.
+		 * Transfer data from FIFO into buffer. Read
+		 * in a tight loop to reduce chance of losing
+		 * FIFO data when the i3c speed is high.
 		 */
-		rx_count = mcux_i3c_fifo_rx_count_get(base);
-		while (rx_count > 0) {
-			uint8_t data = (uint8_t)base->MRDATAB;
-
-			if (offset < buf_sz) {
-				buf[offset] = data;
-				offset += 1;
-			} else {
-				overflow = true;
+		while (offset < buf_sz) {
+			if (mcux_i3c_fifo_rx_count_get(base) == 0) {
+				break;
 			}
-
-			rx_count -= 1;
+			buf[offset++] = (uint8_t)base->MRDATAB;
 		}
 	}
 
-	if (overflow) {
-		ret = -EINVAL;
-	} else {
-		ret = offset;
-	}
+	ret = offset;
 
 one_xfer_read_out:
 	return ret;