AM3358: UART FIFO Trigger Level Issue

I am using AM3358 (Beaglebone Black). Facing issue to configure UART FIFO trigger level. 

 pseudo code

Set FCR -> 0xC1           ' FC[76,7] = 3  => 60 character  

while

TLR = 0

SCR[7] RXTRIGGRANU1   = 0

if  360 byte are receive  then 6 interrupts occurred that fine but set if  FCR =   0x41  "16 characters"  still we have 6 interrupts at receiving 360 bytes.

we have consider the modes to set the corresponding registers.

is there any special sequence to configure the FIFO trigger level.

Is there any example code to test the different FIFO levels.