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su.li@bd.com
Observer
Observer
1,242 Views
Registered: ‎10-18-2018

Add a UART, but TTY driver not working

Hi,

I tried to add a UART IP to my Zynq board. First I added an axi_uartlite IP and built FPGA and Linux image, but I couldn't see any TTY device created under /dev/ttyxx. Then I added an axi_uart16550 IP and rebuilt FPGA and Linux image. I saw 4 TTY devices were created. But I tested these 4 TTYs, only ttyS3 worked.  Please see the attached screen shot. Can any one help to explain this and guide how to create a UART device and tty driver. Thanks!

UartIssuejpg.jpg
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5 Replies
pvenugo
Moderator
Moderator
1,136 Views
Registered: ‎07-31-2012

Hi su.li@bd.com,

Make sure you enable axi uartlite driver in menu config to see ttyULx in the list.

Refer to https://xilinx-wiki.atlassian.net/wiki/spaces/A/pages/18842249/Uartlite+Driver

Regards

Praveen


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su.li@bd.com
Observer
Observer
1,111 Views
Registered: ‎10-18-2018

Thanks for reply! I will try this. Is the  CONFIG_SERIAL_UARTLITE variable already in some .config file? I couldn't find it.

# integrate into the kernel

CONFIG_SERIAL_UARTLITE=y

In addition, this potentially solves my first part of issues. My second part is why axi_uart16550 IP would create 4 device? Please see my design and question screen shot. 

 

 

AddTwoUartIssuejpg.jpg
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pvenugo
Moderator
Moderator
1,094 Views
Registered: ‎07-31-2012

Hi su.li@bd.com,

Try root@zcu102:~# dmesg |grep serial and see what result you are getting back.

Regards

Praveen

 


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gudishak
Moderator
Moderator
1,089 Views
Registered: ‎06-27-2017

su.li@bd.com,

To add more along with pvenugo, could you please check whether driver got probed as mentioned in wiki

 

[   16.039167] Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled
[   16.230793] 800c0000.serial: ttyUL0 at MMIO 0x800c0000 (irq = 209, base_baud = 0) is a uartlite
[   16.485540] of_serial 800b0000.serial: FAILED to find out alias id
[   16.676807] 800b0000.serial: ttyS0 at MMIO 0x800b1000 (irq = 211, base_baud = 6250000) is a 16550A
Best Regards
Kranthi
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su.li@bd.com
Observer
Observer
1,048 Views
Registered: ‎10-18-2018

Thanks suggstions. You can see if I run ls /dev/tty*, I would see 4 devices. However, if run dmesg | grep serial, only one. 

UartDmesg.jpg
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