mtd:mxs:nand calculate ecc strength dynamically

Calculate ecc strength according oobsize, but not hardcoded
which is not aligned with kernel driver
Signed-off-by: NPeng Fan <Peng.Fan@freescale.com>
Signed-off-by: NYe.Li <b37916@freescale.com>
Reviewed-by: NMarek Vasut <marex@denx.de>
Signed-off-by: NJörg Krause <joerg.krause@embedded.rocks>

drivers/mtd/nand/mxs_nand.c

@@ -146,26 +146,20 @@ static uint32_t mxs_nand_aux_status_offset(void)
 static inline uint32_t mxs_nand_get_ecc_strength(uint32_t page_data_size,
 						uint32_t page_oob_size)
 {
-	if (page_data_size == 2048) {
-		if (page_oob_size == 64)
-			return 8;
+	int ecc_strength;
 
-		if (page_oob_size == 112)
-			return 14;
-	}
-
-	if (page_data_size == 4096) {
-		if (page_oob_size == 128)
-			return 8;
-
-		if (page_oob_size == 218)
-			return 16;
-
-		if (page_oob_size == 224)
-			return 16;
-	}
+	/*
+	 * Determine the ECC layout with the formula:
+	 *	ECC bits per chunk = (total page spare data bits) /
+	 *		(bits per ECC level) / (chunks per page)
+	 * where:
+	 *	total page spare data bits =
+	 *		(page oob size - meta data size) * (bits per byte)
+	 */
+	ecc_strength = ((page_oob_size - MXS_NAND_METADATA_SIZE) * 8)
+			/ (13 * mxs_nand_ecc_chunk_cnt(page_data_size));
 
-	return 0;
+	return round_down(ecc_strength, 2);
 }
 
 static inline uint32_t mxs_nand_get_mark_offset(uint32_t page_data_size,