can: c_can: Update D_CAN TX and RX functions to 32 bit - fix Altera Cyclone access

commit 427460c8 upstream.

When testing CAN write floods on Altera's CycloneV, the first 2 bytes
are sometimes 0x00, 0x00 or corrupted instead of the values sent. Also
observed bytes 4 & 5 were corrupted in some cases.

The D_CAN Data registers are 32 bits and changing from 16 bit writes to
32 bit writes fixes the problem.

Testing performed on Altera CycloneV (D_CAN).  Requesting tests on other
C_CAN & D_CAN platforms.
Reported-by: Richard Andrysek <richard.andrysek@gomtec.de>
Signed-off-by: Thor Thayer <tthayer@opensource.altera.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/net/can/c_can/c_can.c

@@ -331,9 +331,23 @@ static void c_can_setup_tx_object(struct net_device *dev, int iface,
 
 	priv->write_reg(priv, C_CAN_IFACE(MSGCTRL_REG, iface), ctrl);
 
+	if (priv->type == BOSCH_D_CAN) {
+		u32 data = 0, dreg = C_CAN_IFACE(DATA1_REG, iface);
+
+		for (i = 0; i < frame->can_dlc; i += 4, dreg += 2) {
+			data = (u32)frame->data[i];
+			data |= (u32)frame->data[i + 1] << 8;
+			data |= (u32)frame->data[i + 2] << 16;
+			data |= (u32)frame->data[i + 3] << 24;
+			priv->write_reg32(priv, dreg, data);
+		}
+	} else {
 		for (i = 0; i < frame->can_dlc; i += 2) {
-		priv->write_reg(priv, C_CAN_IFACE(DATA1_REG, iface) + i / 2,
-				frame->data[i] | (frame->data[i + 1] << 8));
+			priv->write_reg(priv,
+					C_CAN_IFACE(DATA1_REG, iface) + i / 2,
+					frame->data[i] |
+					(frame->data[i + 1] << 8));
+		}
 	}
 }
 
@@ -401,12 +415,22 @@ static int c_can_read_msg_object(struct net_device *dev, int iface, u32 ctrl)
 	} else {
 		int i, dreg = C_CAN_IFACE(DATA1_REG, iface);
 
-		for (i = 0; i < frame->can_dlc; i += 2, dreg ++) {
+		if (priv->type == BOSCH_D_CAN) {
+			for (i = 0; i < frame->can_dlc; i += 4, dreg += 2) {
+				data = priv->read_reg32(priv, dreg);
+				frame->data[i] = data;
+				frame->data[i + 1] = data >> 8;
+				frame->data[i + 2] = data >> 16;
+				frame->data[i + 3] = data >> 24;
+			}
+		} else {
+			for (i = 0; i < frame->can_dlc; i += 2, dreg++) {
 				data = priv->read_reg(priv, dreg);
 				frame->data[i] = data;
 				frame->data[i + 1] = data >> 8;
 			}
 		}
+	}
 
 	stats->rx_packets++;
 	stats->rx_bytes += frame->can_dlc;