mtd: mxc-nand: Do the word to byte mangling in the read_byte callback

When the hardware operates in 16 bit mode it always reads 16 bits even
for operations that only have the lower 8 bits defined. So the upper
bits must be discarded. Do this in the read_byte callback instead of
when reading the NAND id to support reading byte wise more than 5 bytes
and at other occations (like reading the ONFI parameter page).
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/nand/mxc_nand.c

@@ -552,30 +552,17 @@ static void send_page_v1(struct mtd_info *mtd, unsigned int ops)
 
 static void send_read_id_v3(struct mxc_nand_host *host)
 {
-	struct nand_chip *this = &host->nand;
-
 	/* Read ID into main buffer */
 	writel(NFC_ID, NFC_V3_LAUNCH);
 
 	wait_op_done(host, true);
 
 	memcpy32_fromio(host->data_buf, host->main_area0, 16);
-
-	if (this->options & NAND_BUSWIDTH_16) {
-		/* compress the ID info */
-		host->data_buf[1] = host->data_buf[2];
-		host->data_buf[2] = host->data_buf[4];
-		host->data_buf[3] = host->data_buf[6];
-		host->data_buf[4] = host->data_buf[8];
-		host->data_buf[5] = host->data_buf[10];
-	}
 }
 
 /* Request the NANDFC to perform a read of the NAND device ID. */
 static void send_read_id_v1_v2(struct mxc_nand_host *host)
 {
-	struct nand_chip *this = &host->nand;
-
 	/* NANDFC buffer 0 is used for device ID output */
 	writew(host->active_cs << 4, NFC_V1_V2_BUF_ADDR);
 
@@ -585,15 +572,6 @@ static void send_read_id_v1_v2(struct mxc_nand_host *host)
 	wait_op_done(host, true);
 
 	memcpy32_fromio(host->data_buf, host->main_area0, 16);
-
-	if (this->options & NAND_BUSWIDTH_16) {
-		/* compress the ID info */
-		host->data_buf[1] = host->data_buf[2];
-		host->data_buf[2] = host->data_buf[4];
-		host->data_buf[3] = host->data_buf[6];
-		host->data_buf[4] = host->data_buf[8];
-		host->data_buf[5] = host->data_buf[10];
-	}
 }
 
 static uint16_t get_dev_status_v3(struct mxc_nand_host *host)
@@ -719,9 +697,17 @@ static u_char mxc_nand_read_byte(struct mtd_info *mtd)
 	if (host->status_request)
 		return host->devtype_data->get_dev_status(host) & 0xFF;
 
-	ret = *(uint8_t *)(host->data_buf + host->buf_start);
-	host->buf_start++;
+	if (nand_chip->options & NAND_BUSWIDTH_16) {
+		/* only take the lower byte of each word */
+		ret = *(uint16_t *)(host->data_buf + host->buf_start);
+
+		host->buf_start += 2;
+	} else {
+		ret = *(uint8_t *)(host->data_buf + host->buf_start);
+		host->buf_start++;
+	}
 
+	pr_debug("%s: ret=0x%hhx (start=%u)\n", __func__, ret, host->buf_start);
 	return ret;
 }