BCH ECC decoder for Qualcomm NAND controller

qcom_nandc_decoder.py

#!/usr/bin/env python3
# BCH ECC decoder for Qualcomm NAND controller
# This script assumes no bad block on flash
# Ref:
# https://elixir.bootlin.com/linux/latest/source/drivers/mtd/nand/raw/qcom_nandc.c
# https://github.com/ecsv/qcom-nandc-pagify

import bchlib

# 128MiB Flash, Page Size：2048+128
page_size = 2048
oob_size = 128
page_count = 128 * 1024 * 1024 // page_size

# 8-Bit BCH, 8x bus: 13 bytes ECC
bbm_size = 1
ecc_bits = 8

chunk_count = page_size // 512
chunk_size = 532 if ecc_bits == 8 else 528
data_size = 516
data1_size = page_size - (chunk_count - 1) * chunk_size
data2_size = data_size - data1_size

bch = bchlib.BCH(8219, ecc_bits)

f = open('nand-dump.bin', 'rb')
fo = open('decoded.bin', 'wb')
for page in range(page_count):
    for chunk in range(chunk_count):
        data = bytearray(f.read(data1_size))
        f.read(bbm_size)
        data += f.read(data2_size)
        ecc = bytearray(f.read(bch.ecc_bytes))
        bit_flip = bch.decode_inplace(data, ecc)
        if (bit_flip > 0):
            print('ecc corrected ' + bit_flip + 'bits on page ' + page + ' chunk ' + chunk)
        elif (bit_flip < 0):
            print('uncorrectable ecc at page ' + page + ' chunk ' + chunk)
        
        if (chunk == chunk_count - 1):
            fo.write(data[:-4 * chunk_count])
        else:
            fo.write(data)
        f.read(chunk_size - data_size - bbm_size - bch.ecc_bytes)
    f.read(page_size + oob_size - chunk_size * chunk_count)