UART2 hardware flow control


Hello everyone,

I have a HiKey LeMaker board running a debian image (20160629) with kernel 4.4.
Currently I try to get the UART 2 (/dev/ttyAMA2, Low Speed Expansion Connector 3, 5, 7, 9) to work with hardware flow control.
It is possible to communicate without flow control, so RX and TX are connected correctly to the other device.
If flow control is turned on, only the HiKey is able to send something, receiving does not work. I assume this is because RTS is high.
Now I am wondering why RTS is always high? Was someone able to get UART 2 to work with hardware flow control?

I tried to set RTS (gpio 13.7 = 407) manually with /sys/class/gpio after disabling UART 2 in the dtb (uart@f7114000 status = “disabled”) but the pin was always high. I checked pinmux-pins, pin 54 - 57 are not used by uart. The other pins (13.6, 14.0, 14.1 = 406, 392, 393) can be controlled by exporting, setting the direction and finally setting the value. Does someone know how to get 0V at gpio 407, or can confirm that it is not possible?

Thanks for your help


Asked hisilicon to help this.
Thanks for bring this to us.