UART 2 RX receive problems in AM335x Linux.

Hi Forum,

I've a strange problem using the UART2 on a beaglebone using ti-sdk-am335x-evm-06.00.00.00.

The pin initialisation in board-am335xevm.c got changed. 

I added {uart2_init, DEV_ON_BASEBOARD, PROFILE_NONE}, in beaglebone_dev_cfg[]

I checked the states of the pin's and they seem to be correct.

root@am335x-evm:/sys/kernel/debug/omap_mux# cat spi0_sclk 
name: spi0_sclk.uart2_rxd (0x44e10950/0x950 = 0x0071), b NA, t NA 
mode: OMAP_MUX_MODE1 | AM33XX_PIN_INPUT_PULLUP | AM33XX_SLEWCTRL_SLOW 
signals: spi0_sclk | uart2_rxd | i2c2_sda | NA | NA | NA | NA | gpio0_2

root@am335x-evm:/sys/kernel/debug/omap_mux# cat spi0_d0 
name: spi0_d0.uart2_txd (0x44e10954/0x954 = 0x0059), b NA, t NA 
mode: OMAP_MUX_MODE1 | AM33XX_SLEWCTRL_SLOW 
signals: spi0_d0 | uart2_txd | i2c2_scl | NA | NA | NA | NA | gpio0_3

Now I can send messages via e.g.

   echo "hello world" > /dev/ttyO2

and this is received correctly at the RX side.

But when I try to receive messages sent to the beaglebone, then it becomes strange. There are only parts of the message received correctly. The rest is complete garbage. 

We tested all different baud rates and also different tools. I compiled minicom, I compiled a termios example and also did a cat < /dev/ttyO2 and all results in the same.

We narrowed the issue down to the fact, that the 2 first characters are always correct. The rest .... unusable. 

So we wonder what could cause this behaviour? Can the DMA (edma_req) or some timings or buffers cause this?

Any ideas or suggestions?

Thanks,

Florian