How to enable uart0 in rock 3a?

#1

I uart the PIN with by this link:
https://wiki.radxa.com/Rock3/dev/libmraa
https://wiki.radxa.com/Rock3/hardware/3a/gpio
So I try:
PIN22 UART0_TX
PIN15 UART0_RX

Then I add “rk3568-uart0” to “overlays=” line in /boot/uEnv.txt, and I can found it in /dev/ttyS0, but I can’t use it:

rock@rock-3a:~$ ls /dev/ttyS*
/dev/ttyS0  /dev/ttyS1
rock@rock-3a:~$ sudo echo hello > /dev/ttyS0
-bash: /dev/ttyS0: Permission denied
rock@rock-3a:~$ sudo cat /dev/ttyS0
[sudo] password for rock:
[  163.196411] of_dma_request_slave_channel: dma-names property of node '/serial@fdd50000' missing or empty
^C
rock@rock-3a:~$ dmesg | grep "ttyS0"
[    0.506893] fdd50000.serial: ttyS0 at MMIO 0xfdd50000 (irq = 16, base_baud = 1500000) is a 16550A
[  163.196553] ttyS0 - failed to request DMA, use interrupt mode
[  163.198099] ttyS0 set divisor fail, quot:156 != dll,dlh:0
rock@rock-3a:~$
#2

I have similar problem with CM3 Industrial module. I tried to activate several UART’s but all of them give error like this:

ttyS6 set divisor fail, quot:156 != dll,dlh:0
#3

the similar problem in rock 5b …Enabling/using secondary UART

#4

the docs by offical is so terrible