Phone refused to start/now has cryptic msg & has been downloading something for hours!

[Android Central Question]

Hello.

I have a Galaxy Note 4. It had 72% battery remaining.

When my alarm went off today, whereas normally the screen illuminates allowing one to swipe the alarm off, today the screen wouldn't activate.
I tried pressing the power button to start the screen, but no joy. Tried keeping it pressed to see if that would force the restart/power off option menu, but again no joy.
I removed the battery and replaced it. No joy.
I used a spare battery and it started up with a screen saying...

Could not do normal reboot.
ddi:mmc_read failed
QDIN MODE (HIGH SPEED)
Product name: SM-N910F
Current Binary: Samsung Official
System Status: Custom
Reactivation Lock: Off
Knox Warranty void: 0x0
Qualcom SecureBoot: Enable (CSB)
RP SWREV: S1, T1, R1, A, P1
Secure download: Enable
VDC Start

Downloading...
Do not turn off target!!

It has now been downloading for over 3 hours.

Does anyone have an idea what happened, what caused it, how long should the download take, if there is anything I should do or look for or do & is it likely to work again?

Many thanks.

 

[belodion]

Phone refused to start/now has cryptic msg & has been downloading something for hours!

Try holding Power to power off, then power on normally from there.