I have an imx53 QSB and added a custom expansion board so I can access the signals for UART4 and UART 5 RXD and TXD. When I run dmesg | grep tty, I can see ttymxc3 at MMIO 0x53ff000 (irq = 13) and ttymxc4 at MMIO 0x63f90000 (irq =86).
My test application tries to write "TEST" to the UART a thousand times but when I look at signal with an oscilloscope, nothing shows up. If I direct the output of my application to UART1 (ttymxc0), then I see the correct output.
There was a discussion in Nov 2011 that showed how changes may need to be made to board-mx53_loco.c However, in that instance, it seemed like nothing came back when issuing dmesg, which is not the case in my instance.
Is there something else I have to do to enable UART5? Do I have to configure the output pin to UART function? If so, how do I do this?