Bootloop and locked bootloader, how to restore data/unlock?

[Cestis]

Hey. I tried to install an update for MIUI on my Mi4C and ended up getting into a bootloop with locked bootloader. I've never logged in into any Mi account on the device, and MiUnlock says that I cannot unlock it (tried both methods from "[Unlock BL] Mi Devices Bootloader Unlocking FAQ: Announcement, Troubleshoot, and Tips" thread on eu.miui.com, can't post URLs).

Is there any way to access my data, or unlock my device without data loss? Thank you!

 

[k23m]

Is there any way to access my data, or unlock my device without data loss? Thank you!

Hi, it's doable, but if you were on MIUI9+ it will be difficult. Basically you have to enter the EDL mode and flash a modified ROM. On an old MIUI you enter EDL with "fastboot oem edl" but on MIUI9+ with hardware test point method - please refer to:
https://www.smartphones.how/repair/edl-mode
and
https://www.arenaflashing.com/2017/12/test-point-xiaomi-mi4c.html
Try "fastboot oem edl" anyway.

When you're in EDL follow https://forum.xda-developers.com/mi-4c/general/guide-unlocking-mi4c-bl-verification-t3336779
but since you want to preserve your data you need to modify libra_images_6.1.7... a bit. Just delete the following line from "rawprogram0.xml"

<program SECTOR_SIZE_IN_BYTES="512" file_sector_offset="0" filename="userdata.img" label="userdata" num_partition_sectors="0" partofsingleimage="false" physical_partition_number="0" readbackverify="false" size_in_KB="0" sparse="true" start_byte_hex="0xc4000000" start_sector="6422528"/>

Also delete the "userdata.img" file before flashing. OK?
Then run the old MIUI, backup your data and then unlock.