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imx53 UART SDMA under Linux mainline is broken

Question asked by Rick Bronson on Sep 4, 2014
Latest reply on Sep 17, 2014 by Fabio Estevam



  In the mainline kernel, UART SDMA is only enabled for imx6.  It seems to work just fine for imx53 in 2.6.35 so there shouldn't be any hardware problem in trying to get it working in mainline.  I enabled it and the tx callback happens at the right frequency and the serial driver stats look correct via "cat /proc/tty/driver/IMX-uart" but oddly no char's appear at the TX pin using an oscilloscope.   I made sure they appear when SDMA is turned off using the same test program.  The script binaries are the same between 2.6.35 and mainline and the firmware is getting loaded okay via dmesg:


imx-sdma 63fb0000.sdma: loaded firmware 1.1
imx-sdma 63fb0000.sdma: initialized


  Anyone have any clues to what's happening or how to go about getting it working?


  Thanks much for any help.