What's P1 and P2 board?

The Flashing the Bootloader Connecting the DB820c section says:

If you have a P2 board (or above, which is the most likely situation), set it to ON,OFF,OFF,ON. Otherwise, if you have a P1 board, set it to ON,ON,OFF,ON

What’s P1 and P2 board?
On the back of the board I have 3 identifiers:

  • MP25-P2214-2 REV A
  • 25-P2214-P1 REV A
  • PWB. MAIN. P4 DB820C. SBC. APQ8096

Do I have a P1 or P4 board?

there have been various revisions of the board since the early days. P1 was the very first prototype, then we saw P2 and P4. I think P1 and P2 were very restricted in terms of distribution. P4 are the one most people out there should have (and the one that Arrow is currently selling). the changes between the boards were ‘small’ h/w bug fixes most of the time with little impact on the software.