Yes, Viola can be powered using pin 1 of the connector X9. Please ensure only 5V power supply is used to power up the Viola carrier board.
It is also important to note that connector X9 pins are rated for 2.5A. If the total power required by the system is more than 2.5A, we recommend you to use connector X2 or X3 to power up the board.
For more details, please refer to section : Electrical Characteristics in the Viola carrier board datasheet.
Let us know, if you have any other query.