qdma can't access on chip memory ( L2 RAM)

hi,experts!

I have a codec engine examples doing video encode.
In my codec, I use qdma to copy data between L2 RAM and DDR so that it can speed up.

The problem is qdma transfer between L2 RAM and DDR, it works wrong.but when qdma is between two DDR address it works right.

I try the way TI emploree Gunjan said.  below:

1,DMAN3.queuePri=[2,2];

2,adding offset 0x30000000 to L2RAM address(like 0x10800000 ---->0x40800000);

But it still works wrong.In detail, the data it transfered is always zero!

How to  solve it? Hope your help urgently!

My board is C6a8168 evm board.

francis