memory: mvebu-devbus: fix the conversion of the bus width

According to the Armada 370 and Armada XP datasheets, the part of the
Device Bus register that configure the bus width should contain 0 for
a 8 bits bus width, and 1 for a 16 bits bus width (other values are
unsupported/reserved).

However, the current conversion done in the driver to convert from a
bus width in bits to the value expected by the register leads to
setting the register to 1 for a 8 bits bus, and 2 for a 16 bits bus.

This mistake was compensated by a mistake in the existing Device Tree
files for Armada 370/XP platforms: they were declaring a 8 bits bus
width, while the hardware in fact uses a 16 bits bus width.

This commit fixes that by adjusting the conversion logic.

This patch fixes a bug that was introduced in
3edad321 ('drivers: memory: Introduce
Marvell EBU Device Bus driver'), which was merged in v3.11.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Link: https://lkml.kernel.org/r/1397489361-5833-2-git-send-email-thomas.petazzoni@free-electrons.com
Fixes: 3edad321 ('drivers: memory: Introduce Marvell EBU Device Bus driver')
Cc: stable@vger.kernel.org # v3.11+
Acked-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Acked-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>

drivers/memory/mvebu-devbus.c

@@ -108,8 +108,19 @@ static int devbus_set_timing_params(struct devbus *devbus,
 			node->full_name);
 		return err;
 	}
-	/* Convert bit width to byte width */
-	r.bus_width /= 8;
+
+	/*
+	 * The bus width is encoded into the register as 0 for 8 bits,
+	 * and 1 for 16 bits, so we do the necessary conversion here.
+	 */
+	if (r.bus_width == 8)
+		r.bus_width = 0;
+	else if (r.bus_width == 16)
+		r.bus_width = 1;
+	else {
+		dev_err(devbus->dev, "invalid bus width %d\n", r.bus_width);
+		return -EINVAL;
+	}
 
 	err = get_timing_param_ps(devbus, node, "devbus,badr-skew-ps",
 				 &r.badr_skew);