[FS#3887] MTD partition offset not correctly mapped when bad eraseblocks present

[OpenWrt Bugs]

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A new Flyspray task has been opened.  Details are below. 

User who did this - csharper2005 (csharper2005) 

Attached to Project - OpenWrt/LEDE Project
Summary - MTD partition offset not correctly mapped when bad eraseblocks present
Task Type - Bug Report
Category - Kernel
Status - Unconfirmed
Assigned To - 
Operating System - All
Severity - High
Priority - Very Low
Reported Version - Trunk
Due in Version - Undecided
Due Date - Undecided
Details -  - Device problem occurs on:
  * Beeline Smartbox GIGA with bad erase block on NAND flash
  * Possible other NAND devices with bad erase blocks on flash 
 - Software versions of OpenWrt/LEDE release, packages, etc:
OpenWrt SNAPSHOT r16952-677813c776
 - Steps to reproduce:
1. Write Openwrt kernel (mtd4) and UBI (mtd6) partitions from the stock firmware on a device with badblock(s).
2. Get bootloop:
[    4.040886] mt7530 mdio-bus:1f: Link is Up - 1Gbps/Full - flow control off
[    4.042039] UBI error: no valid UBI magic found inside mtd6
[    4.065746] hctosys: unable to open rtc device (rtc0)
[    4.076584] /dev/root: Can't open blockdev
[    4.084755] VFS: Cannot open root device "(null)" or unknown-block(0,0): error -6

Root cause:
1. Both U-Boot and stock firmware detects a bad eraseblock, all following offsets are sifted by one block (0x20000). Our mtd4 and mtd6 in fact are written at 0x420000 and 0x1020000.
********************************************
Flash Map Information
********************************************
Partition           Logic_Offs  Logic_size  Real_Offs   Real_Size
u-boot              0           100000      0           100000
part_map            100000      100000      100000      100000
factory-data        200000      100000      200000      120000
dual-flag           300000      100000      320000      100000
uImage1             400000      600000      420000      600000
uImage2             a00000      600000      a20000      600000
rootfs1             1000000     1800000     1020000     1800000
rootfs2             2800000     1800000     2820000     1800000
config/log          4000000     800000      4020000     800000
app-tmp             4800000     c00000      4820000     c00000
free-space          5400000     2800000     5420000     2800000
badblock-reserve    7c00000     400000      7c20000     360000
2. U-Boot still waiting for a kernel at 0x420000 and it's ok.
3. Openwrt detects a bad eraseblock, but does NOT shift all following offsets by one block:
[    1.198092] nand: device found, Manufacturer ID: 0xc2, Chip ID: 0xf1
[    1.210738] nand: Macronix MX30LF1G18AC
[    1.218369] nand: 128 MiB, SLC, erase size: 128 KiB, page size: 2048, OOB size: 64
[    1.233435] mt7621-nand 1e003000.nand: ECC strength adjusted to 4 bits
[    1.246486] mt7621-nand 1e003000.nand: Using programmed access timing: 21005134
[    1.261038] mt7621-nand 1e003000.nand: Using programmed access timing: 21005134
[    1.275588] Scanning device for bad blocks
[    1.312129] Bad eraseblock 22 at 0x0000002c0000
[    2.583817] 8 fixed-partitions partitions found on MTD device mt7621-nand
[    2.597331] Creating 8 MTD partitions on "mt7621-nand":
[    2.607736] 0x000000000000-0x000000100000 : "u-boot"
[    2.618828] 0x000000100000-0x000000200000 : "dynamic partition map"
[    2.632380] 0x000000200000-0x000000300000 : "Factory"
[    2.643531] 0x000000300000-0x000000400000 : "Boot Flag"
[    2.655139] 0x000000400000-0x000000a00000 : "kernel"
[    2.666172] 0x000000a00000-0x000001000000 : "Kernel 2"
[    2.677543] 0x000001000000-0x000007c00000 : "ubi"
[    2.688598] 0x000007c20000-0x000007fa0000 : "bad block reserved"
3. As a result OpenWRT expects to find UBI at 0x1000000. In fact UBI is at 0x10200000. It causes boot loop:

[    4.025957] pci 0000:00:01.0:   bridge window [mem 0x60400000-0x604fffff pref]
[    4.040886] mt7530 mdio-bus:1f: Link is Up - 1Gbps/Full - flow control off
[    4.042039] UBI error: no valid UBI magic found inside mtd6
[    4.065746] hctosys: unable to open rtc device (rtc0)
[    4.076584] /dev/root: Can't open blockdev
[    4.084755] VFS: Cannot open root device "(null)" or unknown-block(0,0): error -6
[    4.099639] Please append a correct "root=" boot option; here are the available partitions:
[    4.116269] 1f00            1024 mtdblock0
[    4.116274]  (driver?)
[    4.129299] 1f01            1024 mtdblock1
[    4.129302]  (driver?)
[    4.142303] 1f02            1024 mtdblock2
[    4.142305]  (driver?)
[    4.155316] 1f03            1024 mtdblock3
[    4.155319]  (driver?)
[    4.168323] 1f04            6144 mtdblock4
[    4.168326]  (driver?)
[    4.181324] 1f05            6144 mtdblock5
[    4.181327]  (driver?)
[    4.194323] 1f06          110592 mtdblock6
[    4.194326]  (driver?)
[    4.207336] 1f07            3584 mtdblock7
[    4.207339]  (driver?)
[    4.220336] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
[    4.236804] Rebooting in 1 seconds..

More information can be found at the following URL:
https://bugs.openwrt.org/index.php?do=details&task_id=3887

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