Starting kernel ...

[    0.000000] Linux version 4.14.78 (arny@depc0045) (gcc version 7.3.0 (OpenWrt GCC 7.3.0 r0+8403-fa8e9a8889)) #0 SMP Sun Dec 2 16:35:45 2018
...
[    2.258362] samsung_nand_decode_id: ID is len=6, EC DC 10 95 54 EC EC DC				<-------------------- Info
[    2.263636] samsung_nand_decode_id: original chip->ecc_step_ds=0, chip->ecc_strength_ds=0
[    2.271801] samsung_nand_decode_id: changed  chip->ecc_step_ds=512, chip->ecc_strength_ds=1
[    2.280157] samsung_nand_decode_id: id.data[1] is 0xDC, allowing subpage writes
[    2.287471] nand: device found, Manufacturer ID: 0xec, Chip ID: 0xdc
[    2.293822] nand: Samsung NAND 512MiB 3,3V 8-bit
[    2.298439] nand: 512 MiB, SLC, erase size: 128 KiB, page size: 2048, OOB size: 64
[    2.306695] Bad block table found at page 262080, version 0x01
[    2.312642] Bad block table found at page 262016, version 0x01
[    2.317960] nand_read_bbt: bad block at 0x000004200000
[    2.322955] nand_read_bbt: bad block at 0x0000142c0000
[    2.328249] 16 fixed-partitions partitions found on MTD device 14000000.nand
[    2.335041] Creating 16 MTD partitions on "14000000.nand":
[    2.340553] 0x000000000000-0x000000040000 : "uboot"
[    2.347168] 0x000000040000-0x000003c40000 : "rootfs1"
[    2.353317] 0x000003c40000-0x000004140000 : "kernel"
[    2.358704] 0x000004140000-0x000004240000 : "tmp1"
[    2.363836] 0x000004240000-0x000004440000 : "tmp2"
[    2.368934] 0x000004440000-0x000004540000 : "sysconfig"
[    2.374535] 0x000004540000-0x000004640000 : "ubootconfig"
[    2.380245] 0x000004640000-0x000004700000 : "fwdiag"
[    2.385479] 0x000004700000-0x000004a00000 : "lcdimage"
[    2.391102] 0x000004a00000-0x000004b00000 : "mfgconfig"
[    2.396641] 0x000004b00000-0x000004c00000 : "sipdata"
[    2.401989] 0x000004c00000-0x000008c00000 : "voice"
[    2.408113] 0x000008c00000-0x00001be00000 : "ubi"
[    2.417214] 0x00001be00000-0x00001fa00000 : "rootfs2"
[    2.423419] 0x00001fa00000-0x00001ff00000 : "kernel2"
[    2.428804] 0x00001ff00000-0x000020000000 : "mystery"
[    2.437287] rtl8367b rtl8367b: cannot find mdio bus from bus handle, try again later
...

root@OpenWrt:~# cd /sys/class/mtd/mtd12
root@OpenWrt:/sys/devices/platform/1f400000.fpi/1f400000.fpi:localbus@0/14000000.nand/mtd/mtd12# grep "" *
bad_blocks:1
bbt_blocks:0
bitflip_threshold:1
corrected_bits:0
dev:90:24
ecc_failures:0		I later modified nand_samsung.c and VGV952CJW33-E-IR.dts and removed certain lines...
ecc_step_size:256	seems not to be affected by "chip->ecc_step_ds=512"   in nand_samsung.c or by "nand-ecc-step-size = <256>" in dts
ecc_strength:1		seems not to be affected by "chip->ecc_strength_ds=1" in nand_samsung.c or by "nand-ecc-strength = <3>"    in dts
erasesize:131072
flags:0x400
name:ubi
numeraseregions:0
offset:146800640
oobsize:64
size:320864256
subpagesize:512
type:nand
uevent:MAJOR=90
uevent:MINOR=24
uevent:DEVNAME=mtd12
uevent:DEVTYPE=mtd
uevent:OF_NAME=partition
uevent:OF_FULLNAME=/fpi@10000000/localbus@0/nand@0/partitions/partition@8C00000
uevent:OF_COMPATIBLE_N=0
writesize:2048
root@OpenWrt:/sys/devices/platform/1f400000.fpi/1f400000.fpi:localbus@0/14000000.nand/mtd/mtd12# 

================= from nand_samsung.c

static void samsung_nand_decode_id(struct nand_chip *chip)
{
        struct mtd_info *mtd = nand_to_mtd(chip);

        u8 *d  = chip->id.data;
        printk("samsung_nand_decode_id: ID is len=%d, %02X %02X %02X %02X %02X %02X %02X %02X\n",
               chip->id.len, d[0], d[1], d[2], d[3], d[4], d[5], d[6], d[7]);

        /* New Samsung (6 byte ID): Samsung K9GAG08U0F (p.44) */
        if (chip->id.len == 6 && !nand_is_slc(chip) &&
...
                nand_decode_ext_id(chip);
                if (nand_is_slc(chip)) {
                        switch (chip->id.data[1]) {
                                /* K9F4G08U0D-S[I|C]B0(T00) */
                                case 0xDC:
                                        printk("samsung_nand_decode_id: original chip->ecc_step_ds=%d, chip->ecc_strength_ds=%d\n",
                                               chip->ecc_step_ds, chip->ecc_strength_ds);
                                        chip->ecc_step_ds = 512;
                                        chip->ecc_strength_ds = 1;
                                        printk("samsung_nand_decode_id: changed  chip->ecc_step_ds=%d, chip->ecc_strength_ds=%d\n",
                                               chip->ecc_step_ds, chip->ecc_strength_ds);
                                        if (chip->id.len > 4 &&
                                                (chip->id.data[4] & GENMASK(1, 0)) == 0x1){
                                                chip->options |= NAND_NO_SUBPAGE_WRITE;
                                        } else {
                                                printk("samsung_nand_decode_id: id.data[1] is 0x%02X, allowing subpage writes\n", d[1]);
                                        }
                                break;

                                /* K9F1G08U0E 21nm chips do not support subpage write */
...