mtd: nand: fix generating over-boundary ECC data when writing

When mtk_ecc_encode() is writing the ECC parity data to the OOB
region,because each register is 4 bytes in length,but the len's unit is
in bytes,the operation in the for loop will cross the ECC's boundary.
Signed-off-by: RogerCC Lin <rogercc.lin@mediatek.com>
Fixes: 1d6b1e46 ("mtd: mediatek: driver for MTK Smart Device")
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

drivers/mtd/nand/mtk_ecc.c

@@ -366,7 +366,8 @@ int mtk_ecc_encode(struct mtk_ecc *ecc, struct mtk_ecc_config *config,
 		   u8 *data, u32 bytes)
 {
 	dma_addr_t addr;
-	u32 *p, len, i;
+	u8 *p;
+	u32 len, i, val;
 	int ret = 0;
 
 	addr = dma_map_single(ecc->dev, data, bytes, DMA_TO_DEVICE);
@@ -392,11 +393,14 @@ int mtk_ecc_encode(struct mtk_ecc *ecc, struct mtk_ecc_config *config,
 
 	/* Program ECC bytes to OOB: per sector oob = FDM + ECC + SPARE */
 	len = (config->strength * ECC_PARITY_BITS + 7) >> 3;
-	p = (u32 *)(data + bytes);
+	p = data + bytes;
 
 	/* write the parity bytes generated by the ECC back to the OOB region */
-	for (i = 0; i < len; i++)
-		p[i] = readl(ecc->regs + ECC_ENCPAR(i));
+	for (i = 0; i < len; i++) {
+		if ((i % 4) == 0)
+			val = readl(ecc->regs + ECC_ENCPAR(i / 4));
+		p[i] = (val >> ((i % 4) * 8)) & 0xff;
+	}
 timeout:
 
 	dma_unmap_single(ecc->dev, addr, bytes, DMA_TO_DEVICE);