cros_ec: Handle the single duplex requirement in cros_ec

With several chips using the SPI protocol it seems better to put the single
duplex functionality in the EC rather than the SPI driver.

Signed-off-by: Simon Glass <sjg@chromium.org>

drivers/misc/cros_ec_spi.c

@@ -25,6 +25,8 @@ int cros_ec_spi_packet(struct udevice *udev, int out_bytes, int in_bytes)
 {
 	struct cros_ec_dev *dev = dev_get_uclass_priv(udev);
 	struct spi_slave *slave = dev_get_parentdata(dev->dev);
+	ulong start;
+	uint8_t byte;
 	int rv;
 
 	/* Do the transfer */
@@ -33,10 +35,25 @@ int cros_ec_spi_packet(struct udevice *udev, int out_bytes, int in_bytes)
 		return -1;
 	}
 
-	rv = spi_xfer(slave, max(out_bytes, in_bytes) * 8,
-		      dev->dout, dev->din,
-		      SPI_XFER_BEGIN | SPI_XFER_END);
+	rv = spi_xfer(slave, out_bytes * 8, dev->dout, NULL, SPI_XFER_BEGIN);
+	if (rv)
+		goto done;
+	start = get_timer(0);
+	while (1) {
+		rv = spi_xfer(slave, 8, NULL, &byte, 0);
+		if (byte == SPI_PREAMBLE_END_BYTE)
+			break;
+		if (rv)
+			goto done;
+		if (get_timer(start) > 100) {
+			rv = -ETIMEDOUT;
+			goto done;
+		}
+	}
 
+	rv = spi_xfer(slave, in_bytes * 8, NULL, dev->din, 0);
+done:
+	spi_xfer(slave, 0, NULL, NULL, SPI_XFER_END);
 	spi_release_bus(slave);
 
 	if (rv) {