+ * nand_id_has_period - Check if an ID string has a given wraparound period
+ * @id_data: the ID string
+ * @arrlen: the length of the @id_data array
+ * @period: the period of repitition
+ *
+ * Check if an ID string is repeated within a given sequence of bytes at
+ * specific repetition interval period (e.g., {0x20,0x01,0x7F,0x20} has a
+ * period of 2). This is a helper function for nand_id_len(). Returns non-zero
+ * if the repetition has a period of @period; otherwise, returns zero.
+ */
+static int nand_id_has_period(u8 *id_data, int arrlen, int period)
+{
+ int i, j;
+ for (i = 0; i < period; i++)
+ for (j = i + period; j < arrlen; j += period)
+ if (id_data[i] != id_data[j])
+ return 0;
+ return 1;
+}
+
+/*
+ * nand_id_len - Get the length of an ID string returned by CMD_READID
+ * @id_data: the ID string
+ * @arrlen: the length of the @id_data array
+
+ * Returns the length of the ID string, according to known wraparound/trailing
+ * zero patterns. If no pattern exists, returns the length of the array.
+ */
+static int nand_id_len(u8 *id_data, int arrlen)
+{
+ int last_nonzero, period;
+
+ /* Find last non-zero byte */
+ for (last_nonzero = arrlen - 1; last_nonzero >= 0; last_nonzero--)
+ if (id_data[last_nonzero])
+ break;
+
+ /* All zeros */
+ if (last_nonzero < 0)
+ return 0;
+
+ /* Calculate wraparound period */
+ for (period = 1; period < arrlen; period++)
+ if (nand_id_has_period(id_data, arrlen, period))
+ break;
+
+ /* There's a repeated pattern */
+ if (period < arrlen)
+ return period;
+
+ /* There are trailing zeros */
+ if (last_nonzero < arrlen - 1)
+ return last_nonzero + 1;
+
+ /* No pattern detected */
+ return arrlen;
+}
+
+/*
+ * Many new NAND share similar device ID codes, which represent the size of the
+ * chip. The rest of the parameters must be decoded according to generic or
+ * manufacturer-specific "extended ID" decoding patterns.
+ */
+static void nand_decode_ext_id(struct mtd_info *mtd, struct nand_chip *chip,
+ u8 id_data[8], int *busw)
+{
+ int extid, id_len;
+ /* The 3rd id byte holds MLC / multichip data */
+ chip->cellinfo = id_data[2];
+ /* The 4th id byte is the important one */
+ extid = id_data[3];
+
+ id_len = nand_id_len(id_data, 8);
+
+ /*
+ * Field definitions are in the following datasheets:
+ * Old style (4,5 byte ID): Samsung K9GAG08U0M (p.32)
+ * New Samsung (6 byte ID): Samsung K9GAG08U0F (p.44)
+ * Hynix MLC (6 byte ID): Hynix H27UBG8T2B (p.22)
+ *
+ * Check for ID length, non-zero 6th byte, cell type, and Hynix/Samsung
+ * ID to decide what to do.
+ */
+ if (id_len == 6 && id_data[0] == NAND_MFR_SAMSUNG &&
+ (chip->cellinfo & NAND_CI_CELLTYPE_MSK) &&
+ id_data[5] != 0x00) {
+ /* Calc pagesize */
+ mtd->writesize = 2048 << (extid & 0x03);
+ extid >>= 2;
+ /* Calc oobsize */
+ switch (((extid >> 2) & 0x04) | (extid & 0x03)) {
+ case 1:
+ mtd->oobsize = 128;
+ break;
+ case 2:
+ mtd->oobsize = 218;
+ break;
+ case 3:
+ mtd->oobsize = 400;
+ break;
+ case 4:
+ mtd->oobsize = 436;
+ break;
+ case 5:
+ mtd->oobsize = 512;
+ break;
+ case 6:
+ default: /* Other cases are "reserved" (unknown) */
+ mtd->oobsize = 640;
+ break;
+ }
+ extid >>= 2;
+ /* Calc blocksize */
+ mtd->erasesize = (128 * 1024) <<
+ (((extid >> 1) & 0x04) | (extid & 0x03));
+ *busw = 0;
+ } else if (id_len == 6 && id_data[0] == NAND_MFR_HYNIX &&
+ (chip->cellinfo & NAND_CI_CELLTYPE_MSK)) {
+ unsigned int tmp;
+
+ /* Calc pagesize */
+ mtd->writesize = 2048 << (extid & 0x03);
+ extid >>= 2;
+ /* Calc oobsize */
+ switch (((extid >> 2) & 0x04) | (extid & 0x03)) {
+ case 0:
+ mtd->oobsize = 128;
+ break;
+ case 1:
+ mtd->oobsize = 224;
+ break;
+ case 2:
+ mtd->oobsize = 448;
+ break;
+ case 3:
+ mtd->oobsize = 64;
+ break;
+ case 4:
+ mtd->oobsize = 32;
+ break;
+ case 5:
+ mtd->oobsize = 16;
+ break;
+ default:
+ mtd->oobsize = 640;
+ break;
+ }
+ extid >>= 2;
+ /* Calc blocksize */
+ tmp = ((extid >> 1) & 0x04) | (extid & 0x03);
+ if (tmp < 0x03)
+ mtd->erasesize = (128 * 1024) << tmp;
+ else if (tmp == 0x03)
+ mtd->erasesize = 768 * 1024;
+ else
+ mtd->erasesize = (64 * 1024) << tmp;
+ *busw = 0;
+ } else {
+ /* Calc pagesize */
+ mtd->writesize = 1024 << (extid & 0x03);
+ extid >>= 2;
+ /* Calc oobsize */
+ mtd->oobsize = (8 << (extid & 0x01)) *
+ (mtd->writesize >> 9);
+ extid >>= 2;
+ /* Calc blocksize. Blocksize is multiples of 64KiB */
+ mtd->erasesize = (64 * 1024) << (extid & 0x03);
+ extid >>= 2;
+ /* Get buswidth information */
+ *busw = (extid & 0x01) ? NAND_BUSWIDTH_16 : 0;
+ }
+}
+
+ /*
+ * Old devices have chip data hardcoded in the device ID table. nand_decode_id
+ * decodes a matching ID table entry and assigns the MTD size parameters for
+ * the chip.
+ */
+static void nand_decode_id(struct mtd_info *mtd, struct nand_chip *chip,
+ const struct nand_flash_dev *type, u8 id_data[8],
+ int *busw)
+{
+ int maf_id = id_data[0];
+
+ mtd->erasesize = type->erasesize;
+ mtd->writesize = type->pagesize;
+ mtd->oobsize = mtd->writesize / 32;
+ *busw = type->options & NAND_BUSWIDTH_16;
+
+ /*
+ * Check for Spansion/AMD ID + repeating 5th, 6th byte since
+ * some Spansion chips have erasesize that conflicts with size
+ * listed in nand_ids table.
+ * Data sheet (5 byte ID): Spansion S30ML-P ORNAND (p.39)
+ */
+ if (maf_id == NAND_MFR_AMD && id_data[4] != 0x00 && id_data[5] == 0x00
+ && id_data[6] == 0x00 && id_data[7] == 0x00
+ && mtd->writesize == 512) {
+ mtd->erasesize = 128 * 1024;
+ mtd->erasesize <<= ((id_data[3] & 0x03) << 1);
+ }
+}
+
+ /*
+ * Set the bad block marker/indicator (BBM/BBI) patterns according to some
+ * heuristic patterns using various detected parameters (e.g., manufacturer,
+ * page size, cell-type information).
+ */
+static void nand_decode_bbm_options(struct mtd_info *mtd,
+ struct nand_chip *chip, u8 id_data[8])
+{
+ int maf_id = id_data[0];
+
+ /* Set the bad block position */
+ if (mtd->writesize > 512 || (chip->options & NAND_BUSWIDTH_16))
+ chip->badblockpos = NAND_LARGE_BADBLOCK_POS;
+ else
+ chip->badblockpos = NAND_SMALL_BADBLOCK_POS;
+
+ /*
+ * Bad block marker is stored in the last page of each block on Samsung
+ * and Hynix MLC devices; stored in first two pages of each block on
+ * Micron devices with 2KiB pages and on SLC Samsung, Hynix, Toshiba,
+ * AMD/Spansion, and Macronix. All others scan only the first page.
+ */
+ if ((chip->cellinfo & NAND_CI_CELLTYPE_MSK) &&
+ (maf_id == NAND_MFR_SAMSUNG ||
+ maf_id == NAND_MFR_HYNIX))
+ chip->bbt_options |= NAND_BBT_SCANLASTPAGE;
+ else if ((!(chip->cellinfo & NAND_CI_CELLTYPE_MSK) &&
+ (maf_id == NAND_MFR_SAMSUNG ||
+ maf_id == NAND_MFR_HYNIX ||
+ maf_id == NAND_MFR_TOSHIBA ||
+ maf_id == NAND_MFR_AMD ||
+ maf_id == NAND_MFR_MACRONIX)) ||
+ (mtd->writesize == 2048 &&
+ maf_id == NAND_MFR_MICRON))
+ chip->bbt_options |= NAND_BBT_SCAN2NDPAGE;
+}
+
+/*
+ * Get the flash and manufacturer id and lookup if the type is supported.