Re: [PATCH] mtd: rawnand: nand_base: Handle algorithm selection

[William Zhang]

Hi Linus,

On 01/21/2023 03:43 PM, Linus Walleij wrote:

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.

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

For 1 bit HW ECC, the BRCMNAND driver only uses HAMMING ECC. The brcmnand_setup_dev function should take care of it with just these two properties in the device tress without any code changes: unless these D-Link device has always been using software BCH-1 and wants to continue to use software BCH-1. BTW, I didn't see this change from master branch of linux nand base driver. The "nand-ecc-algo" is only used by the ecc engine code(ecc.c) but this code is not in the u-boot obviously. Were you porting this from a different version of linux nand driver?

Signed-off-by: Linus Walleij <linus.wall...@linaro.org>
---
  drivers/mtd/nand/raw/nand_base.c | 13 ++++++++++---
  1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
index 9eba360d55f3..872b58ec5f23 100644
--- 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;

@@ -4512,10 +4513,13 @@ static int nand_dt_init(struct mtd_info *mtd, struct 
nand_chip *chip, ofnode nod
                        ecc_mode = NAND_ECC_SOFT_BCH;
        }

-               str = ofnode_read_string(node, "nand-ecc-algo");
-               if (str && !strcmp(str, "bch"))
+       str = ofnode_read_string(node, "nand-ecc-algo");
+       if (str && !strcmp(str, "bch")) {
+               ecc_algo = NAND_ECC_BCH;
+               if (ecc_mode == NAND_ECC_SOFT)
                        ecc_mode = NAND_ECC_SOFT_BCH;
+       } else if (!strcmp(str, "hamming")) {
+               ecc_algo = NAND_ECC_HAMMING;
        }

@@ -4529,6 +4533,9 @@ static int nand_dt_init(struct mtd_info *mtd, struct 
nand_chip *chip, ofnode nod
                return -EINVAL;
        }

+               chip->ecc.algo = ecc_algo;
+
        if (ecc_mode >= 0)
                chip->ecc.mode = ecc_mode;

ret = ofnode_read_s32_default(node, "nand-bus-width", -1); - if (ecc_mode == NAND_ECC_SOFT) { ecc_strength = ofnode_read_s32_default(node, + if (ecc_algo >= 0)

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