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Howto get both 8250_omap uart and ompa-serial uart loaded simultaneously.

Matti Kaasinen
Intellectual 660 points

Hi!


I do have both ordinary rs-232 lines and rs-485 lines working simultaneously. I have now managed getting rs-485 mode working by using uart from ompa-serial.c. This gets loade by setting CONFIG_SERIAL_OMAP=y CONFIG_SERIAL_OMAP_CONSOLE=y and commenting out all the CONFIG_SERIAL_8250_ configurations. However, if I uncomment also CONFIG_SERIAL_8250_ options, I will only get 8250 uart loaded. It's true, that omap-serial can work also in rs-232 mode, but I guess that there is reason why 8250 uart was taken as default uart in am335x platforms lately. I believe it is possible to modify "static const struct of_device_id omap_serial_of_match" structure in for instance ompa-serial.c in order to get it loaded with matching compatibly variable in device tree, but I would prefer not to touching kernel code if there is more standard way of doing it.

Do anyone know if there is big difference between performances of these two kernel drivers in rs-232 mode - so that is there any point trying to get these two drivers up and running simultaneously?


Thanks,

Matti

  • 0
    TI__Guru**** 161600 points

    Hi Matti,

    Matti Kaasinen said:

    Do anyone know if there is big difference between performances of these two kernel drivers in rs-232 mode - so that is there any point trying to get these two drivers up and running simultaneously?

    No there is no point in getting these two drivers to work simultaneously. I am not sure it is advised either. 

    The following guide should provide additional information on this: http://processors.wiki.ti.com/index.php/Sitara_Linux_UART_-_Switching_to_8250_Driver

    Best Regards, 

    Yordan

  • 0 in reply to Yordan Kovachev
    Intellectual 660 points

    Thank you for you answer Yordan. I'm familiar with the article you point to and in fact by reversing the hint to get 4850 mode on I got omap-serial with rs-485 working. I did not read the article carefully enough, but really it is told clearly that:

    8250 driver includes several features that are extremely useful for some users right now. The biggest new feature is support for DMA when using UART which significantly increases throughput and reliability while at the same time significantly decreasing CPU load. If you will be transferring alot of data via UART at a very high baud rate then it is recommend to use the 8250 driver.

    Therefore, as I need to use both the plain uart mode and uart with rs-485 mode that is implemented in omap-serial driver, it would really be nice if I could use 8520 driver as "ordinary" uart and omap-serial as rs-485 uart. In fact it seems that uart from 8250 driver is mapped as /dev/ttySx and omap-serial as /dev/ttyOx. Otherwise I'll get "considerable performance loss and CPU load increase"

    Thanks,

    Matti