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UART4 on Cubieboard2 via Overlay not working


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Hi all,


i am trying to enable UART4 on my Cubieboard2 via /boot/armbianEnv.txt:


overlays=i2c1 uart4


but if it seems that my uart4 is not working.


If i look at dmesg | grep tty there is no ttyS4-device - only ttyS0:


[    0.000000] Kernel command line: console=tty1 root=/dev/mmcblk0p1 rootwait rootfstype=ext4 sunxi_ve_mem_reserve=0 sunxi_g2d_mem_reserve=0 sunxi_no_mali_mem_reserve sunxi_fb_mem_reserve=16 hdmi.audio=EDID:0 disp.screen0_output_mode=1920x1080p60 panic=10 consoleblank=0 enforcing=0 loglevel=1
[    0.000860] console [tty1] enabled
[    1.542600] 1c28000.serial: ttyS0 at MMIO 0x1c28000 (irq = 47, base_baud = 1500000) is a U6_16550A


am i doing something wrong or did i forget something?


Thanks for your help!



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I am not sure if it applies with A20 but while using A64, R_UART (which belongs to co-processor, I assume) is enabled when UART4 is selected. Also this problem occurred not on Linux but on U-Boot.

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Hi Gediz,


thanks for your answer.

Regarding R_UART i didnt find anything which did help me with UART4.


The problem not only exists with UART4 - but with all possible UARTs.


If i activate UART2, UART3 for example there is also no entry found in dmesg for ttyS2 or ttyS3.

in dmesg always there is this entry for ttyS0... :-/

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