used gpc-dma instead of memcpy for memory copy

Referring to the dmatest module, I used gpc-dma instead of memcpy for memory copy in my module, but the speed was only 220MB/S. I feel a little incredible, ask GPCDMA in memory copy of the maximum speed can reach?
My environment is Tx2i.
Thanks all!

Could you boost the system by sudo ./jetson_clocks.sh to check again.
Or max the emc clock by below command.

sudo su
echo 1 > /sys/kernel/debug/bpmp/debug/clk/emc/mrq_rate_locked
cat /sys/kernel/debug/bpmp/debug/clk/emc/max_rate
echo {$max_rate} > /sys/kernel/debug/bpmp/debug/clk/emc/rate