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when c states enable in bios,com port detected the receiver buffer overrun at high baudrate in windows 10 RRS feed

  • Question

  • Hi all,

    When i disable the c states in bios , com port were working for high baudrate in windows 10( serial port device has been drived by invox driver)

    When i enable the c states in bios, com port were not working for high baudrate , that time it showing the receive buffer overrun in passmark tool.

    What is the impact when enable the c states which affect the driver were not working in high baudrate for inbox driver?

    how i can fix to resolve the driver to run in high baudrate when we enable the c states in windows 20 by taking the windows sample driver and fix it in driver ?

    Could anyone help on resolving this issue in windows sample driver for serial port ?

    Whether the cpu not able to enter into ACPI c states and how to resolve in driver side?

    Regards,

    Prabhakar Vinayagam


    Prabhakar Vinayagam

    Monday, July 17, 2017 6:39 AM

All replies

  • What is the impact when enable the c states which affect the driver were not working in high baudrate for inbox driver?

    Interrupt latency. As has been explained to you in the OSR list.

    Could anyone help on resolving this issue in windows sample driver for serial port ?

    Yes, someone probably can help, but they would need to see the machine. This cannot be done online in the forum. 

    Just disable these C states and be done with it?

    -- pa

    Monday, July 17, 2017 3:54 PM
  • Hi could you please share the interrupt latency to be used in my driver to come out of this issue of high baudrate were not worked wen we enable the "c" states in BIOS side.

    could you please help on this


    Prabhakar Vinayagam

    Wednesday, July 19, 2017 10:07 AM
  • could you please share the interrupt latency to be used in my driver to come out of this issue of high baudrate 

    Sorry, I don't quite understand your request - Why C states affect interrupt latency, or why interrupt latency causes buffer overrun at high baudrates? Or, how to improve interrupt latency when C states are enabled?

    As for the latter - any power save mechanism is a trade-off for performance. So you (or the end user) should decide what is more important: performance or power saving.  IMHO you just are trying to do something incompatible with C states, or the platform needs fine tuning. You can modify the driver to prevent the system going to C state, without changing BIOS settings; the bottom line will be same: no power saving. You decide.

    -- pa

    Wednesday, July 19, 2017 12:02 PM