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when enable "c" states , COM port were not worked at high baudrate RRS feed

  • Question

  • Hi all,

    When i disable the "c" states in bios side , com port detected the "receive 
    buffer overrun " in windows 10.

    When i enable the "c" states in bios side, cpu is not enter into acpi  c states 
    if the com port used high baudrate to do data transfer in windows 10 where it 
    used the inbox driver.

    How i can fix this issue in windows sample driver 10 of serenum to check the 
    driver enter into acpi c states to fix it were working in high baudrate ?

    when i check in PassMark where com port detected the receive buffer overrun.

    Could you please help on this issue to fix in windows sample driver for serial 
    port.

    Regards,

    Mrutyunjaya

    Friday, August 3, 2018 8:42 PM

Answers

  • The system won't enter power saving C state automatically when CPU load stays high.

    Serial port causes high interrupt rate (at least with the in-box driver), thus it causes high system load. It was not designed to work at high baud rates > 115200.  If you force power saving C state manually, the CPU likely will miss interrupts or data.

    So either do not expect C states working under high load, or remove the load (do not use high baud rates, or try to optimize the driver, do interrupt moderation or whatever).

    Regards,

    -- pa


    • Edited by Pavel A Sunday, August 5, 2018 10:33 AM
    • Marked as answer by MRUTYUNJAYA.M Sunday, August 5, 2018 10:45 AM
    Sunday, August 5, 2018 10:31 AM

All replies

  • You want all these three things together:

    high baudrate without data loss

    - In-box driver

    - C states working

    Looks like you can have only two and give up the 3rd.

    -- pa

    Saturday, August 4, 2018 10:49 PM
  • I did not get properly. Could you please explain little bit more on this ? 

    -Mrutyunjaya

    Sunday, August 5, 2018 5:11 AM
  • The system won't enter power saving C state automatically when CPU load stays high.

    Serial port causes high interrupt rate (at least with the in-box driver), thus it causes high system load. It was not designed to work at high baud rates > 115200.  If you force power saving C state manually, the CPU likely will miss interrupts or data.

    So either do not expect C states working under high load, or remove the load (do not use high baud rates, or try to optimize the driver, do interrupt moderation or whatever).

    Regards,

    -- pa


    • Edited by Pavel A Sunday, August 5, 2018 10:33 AM
    • Marked as answer by MRUTYUNJAYA.M Sunday, August 5, 2018 10:45 AM
    Sunday, August 5, 2018 10:31 AM