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

@@ -871,12 +871,7 @@ 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;
-		}
+		if (prop && len == sizeof(*prop)) {
 			switch (be32_to_cpup(prop)) {
 			case SPI_NBITS_SINGLE:
 				break;
@@ -887,18 +882,16 @@ static void of_register_spi_devices(struct spi_master *master)
 				spi->mode |= SPI_TX_QUAD;
 				break;
 			default:
-			dev_err(&master->dev, "spi-tx-nbits value is not supported\n");
+				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;
-		}
+		if (prop && len == sizeof(*prop)) {
 			switch (be32_to_cpup(prop)) {
 			case SPI_NBITS_SINGLE:
 				break;
@@ -909,10 +902,13 @@ static void of_register_spi_devices(struct spi_master *master)
 				spi->mode |= SPI_RX_QUAD;
 				break;
 			default:
-			dev_err(&master->dev, "spi-rx-nbits value is not supported\n");
+				dev_err(&master->dev,
+					"spi-rx-nbits %d not supported\n",
+					be32_to_cpup(prop));
 				spi_dev_put(spi);
 				continue;
 			}
+		}
 
 		/* Device speed */
 		prop = of_get_property(nc, "spi-max-frequency", &len);