Devices with Qualcomm Snapdragon chipsets feature an alternative boot mode called Emergency Download Mode (EDL), which is strictly intended for OEM servicing. With the right combination of model-specific software binaries (usually referred to as programmers) and EDL flashing tool, it is possible to revive a hard bricked device that has lost Fastboot access. OnePlus, for example, labels their EDL flasher as “MsmDownloadTool”, which is used by customer support representatives to perform a low-level flash on your device to restore the factory firmware. The company has apparently upgraded their repository to support the newly-released OnePlus 8 series, as the MsmDownloadTool for the OnePlus 8 Pro is now up for grabs.
Apart from unbricking, the EDL package is especially useful to carry out a downgrade, as neither the stock recovery nor the local update option of OxygenOS allows end-users to do so. Triggering the EDL boot mode is quite simple – all you need to do is turn off your OnePlus 8 Pro, then hold down both volume up and volume down buttons and plug the phone into your PC. The flasher should detect the phone automatically, otherwise, you need to install the correct driver linked in the thread below. Keep in mind that the flashing tool will wipe your phone, and re-lock the bootloader as well.
Due to the scope of access over the device’s storage, the EDL mode is often exploited by security researchers as well as the modding community. As a preventive measure, companies like Nokia and Xiaomi have imposed server-side lockdowns over the flashing procedure. Fortunately, owners of the OnePlus 8 don’t need to go through all these troubles, and the MsmDownloadTool (based on OxygenOS 10.5.4) even allows cross-flashing the Indian firmware on the global units (and vice-versa). It is still advised to take a backup of the ‘persist’ partition before cross-flashing as the fingerprint scanner may give an error related to some enrollment issues afterward.
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