spi: quad: Make DT properties optional

The addition SPI quad support made the DT properties mandatory, breaking
compatibility with existing systems. Fix that by making them optional,
also improving the error messages while we're at it.
Signed-off-by: Mark Brown <broonie@linaro.org>
Tested-by: Stephen Warren <swarren@nvidia.com>

drivers/spi/spi.c

@@ -871,47 +871,43 @@ static void of_register_spi_devices(struct spi_master *master)
 
 		/* Device DUAL/QUAD mode */
 		prop = of_get_property(nc, "spi-tx-nbits", &len);
-		if (!prop || len < sizeof(*prop)) {
-			dev_err(&master->dev, "%s has no 'spi-tx-nbits' property\n",
-				nc->full_name);
-			spi_dev_put(spi);
-			continue;
-		}
-		switch (be32_to_cpup(prop)) {
-		case SPI_NBITS_SINGLE:
-			break;
-		case SPI_NBITS_DUAL:
-			spi->mode |= SPI_TX_DUAL;
-			break;
-		case SPI_NBITS_QUAD:
-			spi->mode |= SPI_TX_QUAD;
-			break;
-		default:
-			dev_err(&master->dev, "spi-tx-nbits value is not supported\n");
-			spi_dev_put(spi);
-			continue;
+		if (prop && len == sizeof(*prop)) {
+			switch (be32_to_cpup(prop)) {
+			case SPI_NBITS_SINGLE:
+				break;
+			case SPI_NBITS_DUAL:
+				spi->mode |= SPI_TX_DUAL;
+				break;
+			case SPI_NBITS_QUAD:
+				spi->mode |= SPI_TX_QUAD;
+				break;
+			default:
+				dev_err(&master->dev,
+					"spi-tx-nbits %d not supported\n",
+					be32_to_cpup(prop));
+				spi_dev_put(spi);
+				continue;
+			}
 		}
 
 		prop = of_get_property(nc, "spi-rx-nbits", &len);
-		if (!prop || len < sizeof(*prop)) {
-			dev_err(&master->dev, "%s has no 'spi-rx-nbits' property\n",
-				nc->full_name);
-			spi_dev_put(spi);
-			continue;
-		}
-		switch (be32_to_cpup(prop)) {
-		case SPI_NBITS_SINGLE:
-			break;
-		case SPI_NBITS_DUAL:
-			spi->mode |= SPI_RX_DUAL;
-			break;
-		case SPI_NBITS_QUAD:
-			spi->mode |= SPI_RX_QUAD;
-			break;
-		default:
-			dev_err(&master->dev, "spi-rx-nbits value is not supported\n");
-			spi_dev_put(spi);
-			continue;
+		if (prop && len == sizeof(*prop)) {
+			switch (be32_to_cpup(prop)) {
+			case SPI_NBITS_SINGLE:
+				break;
+			case SPI_NBITS_DUAL:
+				spi->mode |= SPI_RX_DUAL;
+				break;
+			case SPI_NBITS_QUAD:
+				spi->mode |= SPI_RX_QUAD;
+				break;
+			default:
+				dev_err(&master->dev,
+					"spi-rx-nbits %d not supported\n",
+					be32_to_cpup(prop));
+				spi_dev_put(spi);
+				continue;
+			}
 		}
 
 		/* Device speed */