Is your model with SD 625 processor? If so, sp tool won't work on it.
If yours is the SD 625 one then you're lucky.
My phone was bricked, stuck on mi logo for hours, this is what I did to flash global fastbootrom and got it up n running. But mine had bootloader unlocked and usb debugging on.
Go to
en.miui.com/a-234.html
1) download MIUI ROM flashing tool
2) download the ROM of your choice from this page.
3) install the flashing tool
4) unzip ROM (use 7zip tool) to the folder where u've installed the tool & rename the parent folder of the ROM to something simple like ROM (usually c:\xiaomi\rom
5) open up the app, select the location of your ROM folder (step 4)
6) press refresh, it should show your device connected
7) choose what you want from the options in the bottom right of the app i.e.
I: clean all > like factory reset, all data gone, brand new or
ii: save user data > this installs the system, but leaves apps n user data intact > if you chose a different ROM then when I had on, can't say if this will be safe to do, better install as fresh.
8) press flash and wait for it to finish.
9) reboot phone, enjoy!
Hope this works