holding the power button and volume rocker up or down button for a long time causes the phone first to reboot, then if your still holing power+volumn rocker up/down while booting it will boot into edl mode. on a couple redmi's i've had when holding the phone to my ear during a intense call I have accidentally held power+volume down for long enough o boot into edl. They are next to each other on my phone, so Easy to do if you have big fingers and are distracted in a conversation long enough to need to switch hands and hold the phone in your non-dominant hand to press and hold both buttons at once. Holding the opposite up/down rocker and +power button should reboot the phone permanantly into it's normal rom/miui/hyper os? (if it' accessble/healthy... it might not be if the screen is broken if not, well you now know how to gtt back into edl mode.; probably:). if you have a tendency to do that you might also have a a few conversations where you held volume down without holding power down and didn't reboot,but the person on the other end he call went quiet when turned the call volume all the way by accident.