5 Replies Latest reply on Apr 13, 2016 12:16 PM by Carlos_A

    Q87 chipset USB Host Controller inter packet delay

    MikeW Green Belt

      Hi,

       

      We are using a Full Speed (12 Mbps) USB Device that has a problem.  When the Device receives an IN token and its response is not ready, it NAKs the token.  This causes the Host Controller to *immediately* (<1us later) re-send the IN packet and get another NAK.  If this process repeats enough, the USB Device can reach a state where it locks up before its DATA response is built.

       

      This is a confirmed problem in the USB Device in that the Host Controller satisfies the min Inter Packet Delay (2 bit time = 167ns) requirement of the USB spec before retrying the NAKed IN token.  However, we are still looking for a workaround in the Q87 and other Intel i7 core chipsets.

       

      Older PCs seem to have a backoff time of 1ms before NAKed packets are retried.  With the introduction of USB 3.0 and the desire to maximize USB throughput, I imagine that the Host Controller backoff time was reduced close to the spec minimum to improve performance.  The USB Device in question works fine in PCs where the Host Controller retry time is 1ms as it has time to build its response.

       

      But I was wondering if this parameter -- the amount of time that the USB Host Controller waits before retrying a NAKed packet -- is somehow configurable.  I am wondering if there is chipset driver, registry parameter, BIOS setting, or firmware that can be modified to affect this behavior.

       

      Any inputs would be appreciated.

       

      Best regards,

      Mike

        • Re: Q87 chipset USB Host Controller inter packet delay
          Carlos_A Brown Belt

          Hello MikeW,

           

          Thank your for contacting the Intel Embedded Community,

           

          In order to help you, we will contact you via email.

           

          Best Regards,

          Carlos_A.

          • Re: Q87 chipset USB Host Controller inter packet delay
            Carlos_A Brown Belt

            Hello MikeW,

             

            Thanks for your reply.

             

            We have received your email.


            In order to better understand this situation, we would like to address the following questions:


            Could you clarify us if this situation happens with your design or with a third party motherboard? In case that it is related to a motherboard, could you please tell us the manufacturer and model of it? If it is your design, could please let us know the complete part number of the processor?


            Could you please update the BIOS and drivers to the latest versions, replicate the listed circumstance, and let us know the effects of these changes? By the way, please provide us the name of the BIOS developer and versions related to the cited situation.


            Could you please inform us if the problem occurs with specific or any USB high Speed device? In case that you disregard this information, please try to reproduce this problem with USB High Speed devices manufactured by different companies, also diverse characteristics, and inform us the outcomes. By the way, please give us all the information of the affected USB devices.


            Please give us all the information requested through the previous questions to better understand this issue.

            Thanks again for your cooperation to solve this case.

            Best Regards,

            Carlos_A.