polling interrupt flag, without activate interrupt

I was working with SPI dma transmision. I config two channels for transmit and receive, however I didn't enable interrupt option in dma, however, before each transmision I cleared tc flag, and then enable spi while polling the tc flag. This works really well.

Now I am trying to do the same for usart, I config the dma peripheral before transmission and reception, and I don't activate the interrupt, but I clear the tc flag for each dma channel. This works well the first time, but second time, rx line does not generate tc flag rise.