[Huawei P9 Guides, News, & Discussion] zgfg:
Ok, flashing from Fastboot to eRecovery (erecovery_ramdisk) fails.

For flashing to eRecovery, Russian TWRP for Honor 9, TWRP-3.2.1.0_Mod_9.img from 4pda was used:

https://4pda.ru/forum/index.php?showtopic=934177&st=60#entry82590973

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Edit: Revised Storage decryption guide:

https://xdaforums.com/showpost.php?p=80029346&postcount=1843

Easier, shorter (no need for Russian TWRP), with Internal memory, NW patch, Face unlock, Magisk and its modules, even ECO Kernel - all surviving decryption (no need to back-up / install and configure them again)

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So, made it for P9 dual SIM, rebranded to EVA-AL10c00b540 Patch02, with Network and Face unlock patches from [MENTION=6870018]Tecalote[/MENTION]

Credits to [MENTION=7447057]rambik33[/MENTION] (made it for DL00c17b540), and to [MENTION=808575]ant0nwax[/MENTION] (experimented and made it also for AL10c00b540)

* From Fastboot, flashed Russian TWRP to Recovery

* Rebooted to Russian TWRP in Recovery and from there:

- Flashed Chinese TWRP, TWRP-8.0.0-EVA-DECRYPTION SUPPORT.img from post #1, to eRecovery

- Flashed also ''regular' [MENTION=2642882]Pretoriano80[/MENTION]'s TWRP P9-EVA-8.0.0-TWRP-v4.img to Recovery

* Rebooted to Chinese TWRP in eRecovery and from there:

- Format Data

- Flashed update_data_full_public.zip (from FullOTA b540), with Success

- Flashed b540-update_full_EVA-AL10_all_cn.zip [MENTION=6870018]Tecalote[/MENTION] provided based on TWRP logs from failing to flash the original update_full_EVA-AL10_all_cn.zip), with Success

- Fix encryption (all in that order)

* Booted to 'new' System to perform basic set-up, without configuring WiFi and accounts, and without restoring apps yet

- Dual SIM worked but VoLTE settings got lost

- Face Unlock settings were present

* Rebooted to Pretoriano's TWRP in Recovery

and/or Chinese TWRP in Recovery

- They both now read Internal memory and Data (as well as Cache, Dalwik) partitions

- Hence, they now also save their settings (check by rebooting to either of them :)

- Flashed (from either of the two TWRPs) Enable-Huawei-OTA.zip and stock Recovery AL10c00b540-Stock-RECOVERY_RAMDIS.img to Recovery

* Rebooted to System and configured WiFi (there was no keyboard, installed GBoard from SD card)

- Settings / About showing Patch02 but System Update notifies for OTA Patch02

- Successfully updated to OTA Patch02 (still with Chinese TWRP in eRecovery)

* Rebooted to Chinese TWRP in eRecovery:

- Flashed (my P9 is dual SIM) EVA-L19_b540-DualSIM_NetworkPatch-v2.6.zip (when you reboot to System you will see that VoLTE settings are present back) and VIE-EVA-FaceUnlock-Oreo-v1.5.zip

- Flashed Russian TWRP to Recovery

* Rebooted to Russian TWRP in Recovery:

- Fllashed stock eRecovery AL10c00b540-Stock-ERECOVERY_RAMDI.img to eRecovery

- Fllashed Pretoriano's (or Chinese, if you wish) TWRP to Recovery

* Rebooted to just flashed TWRP in Recovery:

- Flashed patched Ramdisk for Magisk v19.2

AL10c00b540_Patch02-Magisk_v19_2-Encrypt_AVB-Ramdisk.img (root)

* Rebooted to System, installed Magisk Manager and configured Google account

- SafetyNet ok, Playtore working fine and showing Device Certified

- Now, apps, settings, data can be carefully restored/reinstalled

All resources and utilities can be found on my Mega:

https://mega.nz/#F!JwkVyRya!Rb7OUE0z3PEpXBRxGOM-vQ

NOTE 1:

Procedure as above did not wipe Internal memory (only Data, Dalwik and Cache) but it made Internal memory also accessible to TWRPs

NOTE 2:

Russian TWRP is for Honor 9 and not recommended for Huawei P9, but only that TWRP has the option for flashing to eRecovery (and Fastboot cannot flash to eRecovery either).

Hence, when we need so, we temporarily flash Russian TWRP to Recovery to use it for flashing to eRecovery (Chinese TWRP or back the stock eRecovery), but immediately after, we flash Pretoriano's (or Chinese) TWRP or stock Recovery back to Recovery.