AM3356: UART3 with DMA

Hi Tashiro-san,

Koichiro Tashiro said:

Q1) Could you tell me how to enable DMA for UART3?

First we need to get the DMA channel information from TRM:

- Check Table 11-25 (Crossbar Mapped) shows UART3 uses crossbar event #7 for TX, #8 for RX;

- Check Table 11-24 (Direct Mapped) for any pair of "Open" event numbers which are not used. They will be used in the crossbar configuration for UART3.

The following device tree example shows to use DMA event #34 and #35 for UART3:

 &uart3 {
       dmas = <&edma_xbar 34 0 7
               &edma_xbar 35 0 8>;
       dma-names = "tx", "rx";
 };

Koichiro Tashiro said:

Q2) Can UART3 with DMA support up to 1Mbsp?

Yes, it should.