Ethernet MII mode issue on i.MX8MM (Applied PHY IC : KSZ8081MNX)

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Ethernet MII mode issue on i.MX8MM (Applied PHY IC : KSZ8081MNX)

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ken1
Contributor I

Please see the attached file for detail Picture : Ethernet MII mode issue on i.MX8MM_wKSZ8081MNX_20190904.pptxpastedImage_2.png

* Applied IC

    1) Applied CPU : i.MX8MM (MAC included, possible RGMII/MII)   
    2) Applied PHY IC : KSZ8081MNX (Only MII mode)


1. Symptom
    A) ping communication between [PHY]-[MAC] is impossible (MAC setting : MII mode)

   Picture A.1) : when connecting <TXC line> between [PHY]&[MAC] measuring <TXC line>

   Picture A.2) : when cutting <TXC line> between [PHY]&[MAC] and measuring <TXC line > of PHY side.

   Picture A.3) : when cutting <TXC line> between [PHY]&[MAC] and measuring <TXC line > of MAC side.

   >> 25MHz Clock comes out from PHY side, Clock does not come out from MAC,

        Voltage level decreases when connected to each other

 B) Ping communication between [PHY]&[MAC] is possible, but sometimes disconnection(MAC setting: RGMII)

  Picture B.1) when connecting <TXC line> between [PHY]&[MAC] measuring <TXC line>

    >> 25MHz clock comes outboth PHY & MAC

       So, Ping communication seems sometimes possible because the signal is overlapped,

       but there is a disconnection depending on the voltage level.


2. Review for RGMII vs MII

   1) RGMII : TXC(TxClock) go to from [MAC] to [PHY]

   2) MII : TXC(TxClock) go to from [PHY] to [MAC] > Our Case

3. Symptom prediction

    1) We suspect the setting forENET_TXC“ net(Ball no.: AG24) of i.MX8MM for MII modeseems to be wrong.


4. Request

    1) please sharea patch or SW guide for MII mode.

    2) please share the HW guide for MII mode.  

 

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7 Replies

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igorpadykov
NXP TechSupport
NXP TechSupport

Hi Lee

unfortunately i.MX8M Mini MII mode is not supported in NXP BSPs, no

software examples are available. Recommended to proceed with extended support

of Commercial Support & Engineering Services | NXP for developing patches.

Best regards
igor
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ken1
Contributor I

Hi igor,

[i.MX8M Mini] can support "MII mode" like below (IMX8MMRM.pdf > Page 3673)

pastedImage_2.png

Request) We're appreciated if NXP team guides for the use of "MII mode".

PS) If [i.MX8M Mini]  has a difficulty to support "MII mode", please explain the reason.

Thank you.

BR / Ken 

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fredrichard
Contributor I

Hi Lee,

Did you ever get a sensible answer from NXP? Or did you manage to have the  MII working with the I.MX8 by yourself  at the end?

Thanks

Fred

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vespaman
Contributor III

Hi Fred (Lee),

Did any of you get any futher with this? We are also looking for a way to use MII mode instead of RGMII.

Thanks

  Micael

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igorpadykov
NXP TechSupport
NXP TechSupport

Hi

recently I got update below:

-------------

After confirm with SOC team, both MII and MIILite are not supported by i.MX 8M-Mini.
RM will be updated later.

-------------

sorry for confusion.

Best regards
igor

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igorpadykov
NXP TechSupport
NXP TechSupport

Hi Lee

 

yes hardware supports it, but unfortunately i.MX8M Mini MII mode is not supported in

software - NXP BSPs, because there is no reference board with MII configuration.

For that reason recommended to proceed with extended support

of Commercial Support & Engineering Services | NXP for developing patches.

Best regards
igor

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ken1
Contributor I

I''m  Ken Lee

 who posted above question for  "Ethernet MII mode issue on i.MX8MM (Applied PHY IC : KSZ8081MNX)"

I'm posting additional SW review like below.

1. Review : SW Changes for [RGMII (default) to MII mode]

  * Operating Environment: u-boot Status (not Kernel Status)

  1) To Change Parameter in “imx8mm_evk.h”

      >Before : #define CONFIG_FEC_XCV_TYPE             RGMII

      > After :  #define CONFIG_FEC_XCV_TYPE             MII100 

  2) To Check “register setting value change.

       (Related Register map & SW code like below)

      > Before

          (1) FEC_RCNTRL_FCE  1

          (2) FEC_RCNTRL_MII_MODE  1

          (3) FEC_RCNTRL_RGMII    1

      > After

          (1) FEC_RCNTRL_FCE    1

          (2) FEC_RCNTRL_MII_MODE  1

          (3) FEC_RCNTRL_RGMII     0

2. Request

    1) Please share if additionally Register settings  or additional works are required for the use of MII mode.

pastedImage_1.png

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