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Imx6UL uart DMA TX 4095 Bytes

Question asked by Andrew Kolesnik on Oct 21, 2019
Latest reply on Oct 24, 2019 by igorpadykov


I'm using imx6ul-evk board (i.MX6UltraLite Evaluation Kit | NXP ) with linux 4.9.11. While communication between  board and PC thrue uart with DMA I have a situation that board send to PC all it's Tx buffer - 4095 Bytes (if Tx frame more then 32 Bytes). When I'm turned off a DMA the communication without Tx 4095 Bytes, but board miss regular Tx frame ask. Figure below shows  regular ask and regular answer (1 column its ask + answer not recognize on that scale). I found that software in the board send  ask Tx frame, but uart driver ignore its and then software is fixed answer  timeout (but PC even get not an ask). My qustchion is how can I fix DMA uart (in imx.c) and turn it on to solve problem with regular Tx frame?  uart communication without DMA