[OnePlus 8 Pro  Guides, News, & Discussion] ZedXYZ:
This will not work if your phone bricked after updating to Android 12. You should use the MSM in this case. This guide details downgrading to an earlier version of Android 11 FROM a newer Android 11. You have been warned.

This evening after updating my phone (installing to inactive slot + flashing with Magisk as I have done many times before), I restarted only to receive a Qualcomm CrashDump.

Unlike what I've read online, my one seemed to be a bit more severe. I could not boot into recovery mode (black screen; had to power phone off) and entering Fastboot did not fix the issue. After spending several hours reading through XDA, Stack Overflow, various other sites etc I finally managed to get it fixed. Not only that, but I kept ALL my data AND my root. It's like nothing ever happened.

The issues I faced:

- Mistakenly had USB debugging off (which cannot be enabled when your phone is soft bricked). This made using ADB for initial diagnostics virtually impossible

- Recovery mode showed a black screen; not accessible.

- Installing TWRP, only to find my device passcode (PIN) wasn't allowing me to decrypt my phone data so I could make a backup

- My phone was buggered

How I solved it: Given recovery mode was blank, I flashed TWRP to my recovery drive via Fastboot to bring it back. Because USB debugging was OFF and TWRP wasn't decrypting my data (meaning I couldn't back up any data or download the ROM to my internal storage without wiping it), I activated ADB Sideload within TWRP and then used this to downgrade my version of OxygenOS! After a reboot I received the Qualcomm error one more time, before it continued to boot into OxygenOS with all my data intact.

Your bootloader should already be unlocked. If it isn't, chances are you will be saying goodbye to your data :(

These steps may not work for everybody, but I wanted to give back what I learned from this, and it was rather unconventional and against the grain of what others have suggested. With that said, do so at your own risk.

This is a simple guide. I will explain the tools you will need and how to fix the issue. Anything beyond that (i.e. installing SDK platform tools) can be researched.

This is written assuming you are on Windows, although the steps are generally quite similar.

Tools Needed:

A computer to download and install:

- SDK Platform Tools/ADB (https://developer.android.com/studio/releases/platform-tools)

- TWRP for OnePlus 8 Pro (https://xdaforums.com/t/twrp-3-6-1-11-instantnoodle-twrp-for-oneplus-8-8pro-official-beta.4341707/)

- OnePlus 8 Pro Drivers (You will need this installed if it isn't already for your phone to appear in SDK Platform Tools. You may need to disable driver signature enforcement on Windows 10)

- The version of OxygenOS you were running before the CrashDump occurred (https://xdaforums.com/t/oneplus-8-pro-rom-ota-oxygen-os-repo-of-oxygen-os-builds.4084315/)

Steps to take - Initial Setup and Installation of TWRP:

1. Download everything above and then install SDK Platform Tools + OnePlus 8 Pro Drivers if you don't already have them.

2. Enter Fastboot mode on your phone and then connect it to the computer.

3. Ensure the TWRP .img file is in the same directory as your SDK Platform Tools install

4. Open up command prompt with SDK Platform Tools installed and type in

fastboot devices

Confirm your device ID appears along with "fastboot" beside it.

4. If the device is being recognised, we're ready to install TWRP. Note: Remember your Bootloader must be unlocked for the next steps. While in Fastboot mode, your phone will tell you if your bootloader is locked or unlocked. Now that we've confirmed it is unlocked, Type in:

fastboot flash recovery_a twrpname.img

followed by:

fastboot flash recovery_b twrpname.img

5. You can now boot into recovery mode! On your phone, use the volume keys to navigate and choose Recovery so you can enter TWRP

Downgrading to an older version:

When I installed TWRP, I was horrified to see that I couldn't decrypt my phone with my pin code. Apparently this is an ongoing problem with TWRP and the ability to decrypt your phone data varies between devices and builds of TWRP.

1. Now that you have entered TWRP, enter the "Advanced" settings and enable "ADB Sideload".

2. On the computer, type in

adb devices

. You should see your device appear.

3. Ensure the OxygenOS file is in the same directory as your SDK Platform Tools install

4. Type in

adb sideload updatename.zip

and let it flash to your phone.

And that's it! Reboot your phone. You may receive the Qualcomm error one last time, so kiss that sucker goodbye with a final reboot (I pressed power + volume up but then it continued to boot as normal; much to my surprise) and you should be good to go.

Hope this helps. This is my first ever guide, but my phone bricked itself this afternoon and it took me 3-4 hours of research to figure out what to do. This community played its role in helping me, and I'm sure someone out there will appreciate this information - definitely wanted to give back. I didn't see any information like this outside of wiping the phone entirely... I'm pretty stubborn and didn't want to do that.

This is definitely a "dirty flash", although given I couldn't even boot into the updated version, I would say a downgrade is definitely just fine in this instance.