Thanks I'm actually working on an ADS-based board. The thing is, I know that the GPIO must be muxed that UART5's register must be put into alternate mode. Obviously this board I'm working on is different from the reference platform in that it only has 1 serial port. This is proving to be a challenge because the board has problems working with UART 1 (the default debug port on the LTIB platform) because of bus contention, so the only way is to work with UART 5. I've got this working in u-boot and it is sending and receiving just fine. I've also changed the include/asm/arch/uncompress.h file to point to UART5's base physical address, so when the kernel is decompressing it is printing "uncompressing linux ........ booting.." as it should.
From there on, silence. I've added console=ttymxc4,57600n8 and console=mxcuart,0x43fb4000,57600n8 to the bootargs but still, nothing. Do you perhaps have pointers as to where I should change what so that the kernel pushes all its debug out of UART 5 / ttymxc4?
Let me remind, MX31 ADS board has three UARTs: UART A, UART B and UART C. UART A can be mapped to UART1 or UART5 using the register setting on Peripheral Bus Controller (PBC). UART B can be mapped to UART3 or UART4 using the register setting on PBC. UART C can be mapped to UART1 or UART2 using the register setting on PBC. For more details, refer Peripheral Bus Controller document for MX31 ADS. MX31 UART1 is connected to UART C on MX31 ADS. MX31 UART3 is connected to UART B on MX31 ADS. MX31 UART4 is connected to UART B on MX31 ADS. MX31 UART5 is connected to UART A on MX31 ADS. Since there is a conflict between UART3 and UART4 for connecting to the DB-9 port on MX31 ADS, only one of UART3 and UART4 can be included at a time in the image. Also one should remember about SW1 – UART Enable Switches of the ADS. Default configuration of SW1 is that UART1, UART2, UART3 are enabled (ON), but UART5 is disabled (OFF). As resume : /dev/ttymxc/0 – UART1 of the i.MX31 (UART C) /dev/ttymxc/2 – UART3 of the i.MX31 (UART B) /dev/ttymxc/4 – UART5 of the i.MX31 (UART A) So, set properly the SW1 to enable UART5 and use it as /dev/ttymxc/4). That is, one may connect proper cable between COM port of the PC and UART A (UART 5) and try, for example, the following : stty -F /dev/ttymxc/4 115200 ls>/dev/ttymxc/4 It should work.