mtd: rawnand: nand_base: Handle algorithm selection

For BRCMNAND with 1-bit BCH ECC (BCH-1) such as used on the
D-Link DIR-885L and DIR-890L routers, we need to explicitly
select the ECC like this in the device tree:

  nand-ecc-algo = "bch";
  nand-ecc-strength = <1>;
  nand-ecc-step-size = <512>;

This is handled by the Linux kernel but U-Boot core does
not respect this. Fix it up by parsing the algorithm and
preserve the behaviour using this property to select
software BCH as far as possible.

Reviewed-by: Michael Trimarchi <michael@amarulasolutions.com>
Acked-by: William Zhang <william.zhang@broadcom.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Tom Rini <trini@konsulko.com> [am335x_evm]
Link: https://lore.kernel.org/all/20230407134008.1939717-3-linus.walleij@linaro.org/
Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>

diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
index 9eba360..6b4adcf 100644 (file)
--- a/drivers/mtd/nand/raw/nand_base.c
+++ b/drivers/mtd/nand/raw/nand_base.c
@@ -4487,6 +4487,7 @@ EXPORT_SYMBOL(nand_detect);
 static int nand_dt_init(struct mtd_info *mtd, struct nand_chip *chip, ofnode node)
 {
        int ret, ecc_mode = -1, ecc_strength, ecc_step;
+       int ecc_algo = NAND_ECC_UNKNOWN;
        const char *str;
 
        ret = ofnode_read_s32_default(node, "nand-bus-width", -1);
@@ -4512,10 +4513,22 @@ static int nand_dt_init(struct mtd_info *mtd, struct nand_chip *chip, ofnode nod
                        ecc_mode = NAND_ECC_SOFT_BCH;
        }
 
-       if (ecc_mode == NAND_ECC_SOFT) {
-               str = ofnode_read_string(node, "nand-ecc-algo");
-               if (str && !strcmp(str, "bch"))
-                       ecc_mode = NAND_ECC_SOFT_BCH;
+       str = ofnode_read_string(node, "nand-ecc-algo");
+       if (str) {
+               /*
+                * If we are in NAND_ECC_SOFT mode, just alter the
+                * soft mode to BCH here. No change of algorithm.
+                */
+               if (ecc_mode == NAND_ECC_SOFT) {
+                       if (!strcmp(str, "bch"))
+                               ecc_mode = NAND_ECC_SOFT_BCH;
+               } else {
+                       if (!strcmp(str, "bch")) {
+                               ecc_algo = NAND_ECC_BCH;
+                       } else if (!strcmp(str, "hamming")) {
+                               ecc_algo = NAND_ECC_HAMMING;
+                       }
+               }
        }
 
        ecc_strength = ofnode_read_s32_default(node,
@@ -4529,6 +4542,14 @@ static int nand_dt_init(struct mtd_info *mtd, struct nand_chip *chip, ofnode nod
                return -EINVAL;
        }
 
+       /*
+        * Chip drivers may have assigned default algorithms here,
+        * onlt override it if we have found something explicitly
+        * specified in the device tree.
+        */
+       if (ecc_algo != NAND_ECC_UNKNOWN)
+               chip->ecc.algo = ecc_algo;
+
        if (ecc_mode >= 0)
                chip->ecc.mode = ecc_mode;