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Disabling PING in STATUS stage of USB

JPM
Intellectual 565 points


Hi,

I have been looking at USB traffic between the DM355 and a USB drive and I have observed PING packets in the STATUS stage of a CONTROL transfer. There have been reports of people having issues with these PINGs and certain USB drives. Ideally, it would be nice to turn the PINGs off, however I do not believe the DM355 allows this. The same Linux musb driver is used for both Blackfin and Divinci processors. The Blackfin processor guide defines bit 11 in the HOST_CSR0 register as disabling these PINGs. The DM355 does NOT have this bit defined. My own testing has shown that this bit is ignored by the DM355. There is no other mention of turning off PINGs for EP0.

Has anyone else run into this problem and confirmed these findings? Or found a work around?

 

 

  • 0
    TI__Expert 7435 points

    JPM,

    DM355 is based on Mentor core version 1.3.  Mentor did not support DISPING feature in that core version.

    However appropriate software fixes have been put in in the musb driver to take care of recovery from such scenarios as I remember (at the least in the code that I worked on).

    regards

    swami

  • 0
    TI__Expert 5475 points

    Hi,

    I agree with Swami. You require a Mentor Core version >= 1.4 for PING disable support.

    Just to make sure we are on the same page. The PING support is part of USB 2.0 spec however some devices have not incorporated this feature. The one you can disable is only the control transfer part. HS Bulk is required to support this feature and can not be disabled.

    Best regards, Zegeye