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WFitt's avatar
WFitt
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3 years ago

eSPI Agent Core, bug in WAIT_STATE response

Hello,

We are using Intel eSPI Agent Core in Intel FPGA MAX 10.

Now we possibly found a bug in the Intel eSPI Agent:

The bits 15:12 ("Maximum WAIT STATE Allowed") of the General Capabilites and Configuration Register are set to 0x0 (default value). That means 16 byte time wait states max. are allowed.

The eSPI Agent is responding always 16 bytes of WAIT_STATE before ACCEPT or DEFER regardless of the command responding to.

This behaviour could lead to much lower performance on the eSPI bus!

Regards

Wolfram

13 Replies

  • hareesh's avatar
    hareesh
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    3 years ago

    Hi,

    sorry for late responding.

    can you please share your platform design file and i want to know how did you find out that issue and what steps did you followed. can you please share that information?

    it helps us to identify issue.


    Thanks,


  • WFitt's avatar
    WFitt
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    3 years ago

    Hi,

    we are using an own mainboard with an Intel Elkhart Lake CPU module. The Elkhart Lake CPU is communicating via eSPI with an Intel FPGA on our mainboard. At the moment we use eSPI with 20 MHz eSpi clock and Single I/O mode. The IP clock is 130 MHz.

    During CPU BIOS booting we can see many transactions between Host (CPU) and Agent (FPGA):

    21 00 08 10 GET CONFIGURATION
    21 00 20 C8 GET CONFIGURATION
    22 00 20 01 00 07 00 01 SET CONFIGURATION
    21 00 20 C8 GET CONFIGURATION
    05 1B GET_VWIRE
    21 00 30 B8 GET CONFIGURATION
    22 00 30 00 01 00 00 25 SET CONFIGURATION
    22 00 08 03 00 20 00 95 SET CONFIGURATION
    22 00 20 01 00 07 00 01 SET CONFIGURATION
    22 00 30 00 01 00 00 25 SET CONFIGURATION
    21 00 40 EF GET CONFIGURATION
    22 00 40 0C 11 00 00 F1 SET CONFIGURATION
    04 03 02 70 03 30 41 BA 42 30 11 PUT_VWIRE
    04 01 43 F0 44 F0 DA PUT_VWIRE
    04 03 02 70 03 30 41 BB 42 30 7A PUT_VWIRE
    25 FB GET_STATUS
    05 1B GET_VWIRE
    04 03 02 70 03 30 41 B9 42 30 AC PUT_VWIRE
    04 03 02 74 03 30 41 B9 42 30 D9 PUT_VWIRE
    04 03 02 76 03 30 41 B9 42 30 60 PUT_VWIRE
    04 03 02 77 03 30 41 B9 42 30 BF PUT_VWIRE
    04 03 02 77 03 30 41 B9 42 32 B1 PUT_VWIRE
    04 03 02 77 03 31 41 B9 42 32 D3 PUT_VWIRE
    21 00 10 58 GET CONFIGURATION
    04 03 02 77 03 33 41 B9 42 32 17 PUT_VWIRE
    21 00 10 58 GET CONFIGURATION
    22 00 10 01 11 00 00 F5 SET CONFIGURATION
    45 00 80 15 9B F0 IOWR
    160 other Port 80h I/O writes
    21 00 10 58 GET CONFIGURATION
    22 00 10 17 11 00 00 E6 SET CONFIGURATION
    21 00 10 58 GET CONFIGURATION
    4F FE 0B 00 00 78 56 34 12 FF PUT_MEMWR32_SHORT

    The Agent is responding always with ACCEPT. But always before the ACCEPT response 16 WAIT_STATE are sent by Agent. We detected this issue with oscilloscope and with Intel Quartus SignalTap.

    Regards

    Wolfram

  • hareesh's avatar
    hareesh
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    3 years ago

    Hi,

    i also working on this issue. just for conformation can you please share your platform design file or screenshot


    • WFitt's avatar
      WFitt
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      3 years ago

      Hi,

      In the attachment you can find two screenshots.

      The first is showing a GET_CONFIGURATION command:

      21 00 08 10

      The Agent Core is answering after 16 WAIT_STATEs

      The second attachment is showing a PUT_MEMWR32_SHORT command

      FE 0B 00 00 78 56 34 12 FF

      The Agent Core is answering after 16 WAIT_STATES also.

  • hareesh's avatar
    hareesh
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    3 years ago

    Hi,

    please check bellow attachment. actually wait state value configure by Master please check that

    • WFitt's avatar
      WFitt
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      3 years ago

      Hi,

      bits 15:12 of the General Capabilities and Configurations Register is set to the default value 0000b by the master. This means: Maximum 16 Waite States allowed.

      But this does not mean that the slave has to use 16 Wait States for every (!) response, even for simple accesses like GET_CONFIGURATION.

      But the Intel eSPI Agent core does exactly this!

      Kind Regards

      Wolfram

  • hareesh's avatar
    hareesh
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    3 years ago

    i am debugging that just give me some time.


  • hareesh's avatar
    hareesh
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    3 years ago

    Hi,

    please share you eSPI ip configuration details. like bellow attached one

    i seen 3 cases related to eSPI from you. are you using same ip configuration for all cases for different. if different please share all cases configuration details.

    • WFitt's avatar
      WFitt
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      3 years ago

      Hi,

      I wish you a happy new year!

      I am using the same configuration for all cases:

      Regards

      Wolfram

  • hareesh's avatar
    hareesh
    Icon for Frequent Contributor rankFrequent Contributor
    3 years ago

    Hi,

    may how you are testing this?

    if you are testing on modelsim or questasim pls share project file.

    or else share how your testing processing.



    Thank you,


  • hareesh's avatar
    hareesh
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    3 years ago

    As we do not receive any response from you on the previous question/reply/answer that we have provided. Please login to ‘https://supporttickets.intel.com’, view details of the desire request, and post a feed/response within the next 15 days to allow me to continue to support you. After 15 days, this thread will be transitioned to community support. The community users will be able to help you on your follow-up questions.