The basic Debian install
Nowadays, Debian works natively, although it requires a non-free binary blob to boot. This blob has been packaged since Bullseye in the raspi-firmware package (in Buster and earlier: raspi3-firmware).
For more detailed and historic information on the rpi2, please refer to Debian Jessie on RPi2 article by Sjoerd Simons
Add U-boot to the basic Debian install
The boot blob is required. However, to have a better control of the boot process, you can boot to u-boot.
read https://parobalth.wordpress.com/2015/07/07/raspberry-pi-2-debian-jessie-and-u-boot/ (this approach boots all cores with a recent version of u-boot)
Ready to run
The free driver
kernel driver in development: https://docs.mesa3d.org/drivers/vc4.html
- to be continued
Overclocking the Raspberry Pi 2
Overclocking is quite easy and convenient, and doesn't invalidate your warranty if you don't change voltage. It happens that the actual L2 speed of the Raspberry Pi 2 is severelly underclocked, making the device much more slower that it should actually be. There has been reports of users using overclocked speeds of the processor and the L2 for months without a single issue, but you must be carefull in respecting a good proportion between L2 speed and processor, and overclocking the RAM is generally not recommended.
Try this setting, it has demonstrated to be stable and doubles the speed of this small machine in general. Edit /boot/config.txt and substitute or add these lines:
arm_freq=1000 core_freq=500 sdram_freq=400 over_voltage=0 over_voltage_sdram_p=0 over_voltage_sdram_i=0 over_voltage_sdram_c=0
Unfortunatelly, the options shown when running raspi-config are not quite stable even they are slower than this recommended option.