Qualcomm EDL mode

Screenshot of Device Manager, containing a Qualcomm device booted in the Emergency Download Mode

The Qualcomm Emergency Download mode, commonly known as Qualcomm EDL mode and officially known as Qualcomm HS-USB QD-Loader 9008^[1] is a feature implemented in the boot ROM of a system on a chip by Qualcomm which can be used to recover bricked smartphones.^[2][3] On Google's Pixel 3, the feature was accidentally shown to users after the phone was bricked.^[4]

Device support

See also: Devices using Qualcomm Snapdragon processors

For a device to support EDL it must be using Qualcomm hardware. The Snapdragon family is very widely used.

Access

ADB

The Android Debug Bridge can be utilized to get access to EDL mode, with the command adb reboot edl.^[2]

Windows

The Qualcomm Product Support Tool (QPST) is normally used internally by service center executives for low-level firmware flashing to revive Android devices from a hard-brick or to fix persistent software issues. To flash the firmware, the tool communicates with supported devices via EDL.^{[5][unreliable source?]} The QPST has not been officially released by Qualcomm.^{[citation needed]}

Linux

Qualcomm Download (QDL) is a tool to communicate with Qualcomm System On a Chip bootroms to install or execute code. The source code is maintained by Bjorn Andersson aka andersson.^{[6][non-primary source needed]}

Test points

Qualcomm implemented motherboards always include a test point. These can vary between phone models. Generally, test points are a pair of contacts, which can be some way apart. EDL can be accessed by opening the back of the phone, finding the location of the test point, which depends on the model, and by using a pair of metal tweezers to short the connectors and boot the phone into EDL. Further software tools are needed for actions in EDL mode.

EDL Deep Flash Cable

Qualcomm implemented a feature in motherboards with the presence of EDL, where they can be booted to EDL via an EDL Deep Flash Cable. This specific cable has the general appearance of a button present in the cable. The button can be represented as a switch, to be able to make the phone boot into EDL mode. With the use of the cable, in most devices and cases, it will not be necessary to use the test points. The cable also works on hard-bricked devices to boot them into EDL mode. This cable works by having a button present between D+ and GND.

References

1. Zhao, Longze; Xi, Bin; Wu, Shunxiang; Aizezi, Yasen; Ming, Daodong; Wang, Fulin; Yi, Chao (2018). "Physical Mirror Extraction on Qualcomm-based Android Mobile Devices". Proceedings of the 2nd International Conference on Computer Science and Application Engineering. Hohhot, China: ACM Press. pp. 1–5. doi:10.1145/3207677.3278046. ISBN 978-1-4503-6512-3. S2CID 53038902.
2. EASTTOM, CHUCK (2021). An In-Depth Guide to Mobile Device Forensics. [S.l.]: CRC Press. p. 72. ISBN 978-0-367-63300-4. OCLC 1250310301.
3. Tang, Qinghao (2021). Internet of things security : principles and practice. Fan Du. Singapore. p. 166. ISBN 978-981-15-9942-2. OCLC 1236261208.
4. Amadeo, Ron (2021-09-03). "Reports of Pixel 3s bricking with "EDL" message are growing". Ars Technica. Retrieved 2021-09-11.
5. Bhardwaj, Dhananjay (April 2, 2021). "Download QPST Flash Tool & How to Use it to Flash Firmware on Qualcomm Android Devices". The Custom Droid. Retrieved February 21, 2022.
6. Andersson, Bjorn. "Source code of qdl". Github. Retrieved February 21, 2022.