62e3d6fad9
When three threads run on three different cpu, and write 60 byte to the same uart at the same time, which causes the data loss. After test, it is caused by DMA bursts 16 byte when the fifo is more than 48 byte(fifo total 64 byte). It is solved by clearing the uart dma request before start dma tx. Signed-off-by: Huibin Hong <huibin.hong@rock-chips.com> Change-Id: I4e2099337e25e41a34ceeb9ea774a04cc7c71f07