mtd: nand: add support for "nand-ecc-algo" DT property

So far it was only possible to specify ECC algorithm using "soft" and
"soft_bch" values of nand-ecc-mode prop. There wasn't a way to specify
it for a hardware ECC mode.

Now that we have independent field in NAND subsystem for storing info
about ECC algorithm we may also add support for this new DT property.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

Documentation/devicetree/bindings/mtd/nand.txt

@@ -22,6 +22,8 @@ Optional NAND chip properties:
 - nand-ecc-mode : String, operation mode of the NAND ecc mode.
   Supported values are: "none", "soft", "hw", "hw_syndrome", "hw_oob_first",
   "soft_bch".
+- nand-ecc-algo: string, algorithm of NAND ECC.
+		 Supported values are: "hamming", "bch".
 - nand-bus-width : 8 or 16 bus width if not present 8
 - nand-on-flash-bbt: boolean to enable on flash bbt option if not present false
 

drivers/mtd/nand/nand_base.c

@@ -4003,17 +4003,23 @@ static int of_get_nand_ecc_mode(struct device_node *np)
 	return -ENODEV;
 }
 
+static const char * const nand_ecc_algos[] = {
+	[NAND_ECC_HAMMING]	= "hamming",
+	[NAND_ECC_BCH]		= "bch",
+};
+
 static int of_get_nand_ecc_algo(struct device_node *np)
 {
 	const char *pm;
-	int err;
+	int err, i;
 
-	/*
-	 * TODO: Read ECC algo OF property and map it to enum nand_ecc_algo.
-	 * It's not implemented yet as currently NAND subsystem ignores
-	 * algorithm explicitly set this way. Once it's handled we should
-	 * document & support new property.
-	 */
+	err = of_property_read_string(np, "nand-ecc-algo", &pm);
+	if (!err) {
+		for (i = NAND_ECC_HAMMING; i < ARRAY_SIZE(nand_ecc_algos); i++)
+			if (!strcasecmp(pm, nand_ecc_algos[i]))
+				return i;
+		return -ENODEV;
+	}
 
 	/*
 	 * For backward compatibility we also read "nand-ecc-mode" checking