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Linux/DRA756: speed grade value eFuses are wrong

Francesco Valla
Intellectual 570 points

Part Number: DRA7xx
Other Parts Discussed in Thread: X5777ATXGABC

Tool/software: Linux

Hi,

I'm using a pre-production DRA7xx  sample (marked X5777ATXGABC) and trying to figure out the OPP behavour on Linux 4.4 SDK.

Basically, the kernel reads the silicon version and capabilities from eFuses and set OPP limits; the problem is that the driver expects a value equal to 11, 15 or 23, but on my part the corresponding bits are set to 7 (and thus the kernel limits to NOM_MPU_OPP).

What those numbers stand for? (It's unclear both on the TRM and the Data Manual)

How can I translate 7 to a capability?

Thanks

  • 0
    TI__Intellectual 2330 points
    Hi Francesco,

    Could you please let us know the eFuse registers you are reading?

    Thanks.
    BR,
    Dobrin
  • 0 in reply to Dobrin Dobrinov
    Intellectual 570 points

    Hi Dobrin,

    eFuse register read by the kernel (and checked manually by me) is at 0x4ae0c20c.

    Regards,

    Francesco

  • 0 in reply to Francesco Valla
    TI__Intellectual 2330 points

    Hi Francesco,

    The register should be CTRL_WKUP_STD_FUSE_DIE_ID_2. It is described in "Table 1-3. DRA75x, DRA74x Part Number Identifier" of TRM. You should read the "[23:19] Speed" field. The same table describes what each value of this field means. "Table 3-1. Device Comparison" of DM shows that there are three speed grades: P (Speed field = 15), L (Speed field = 11) and J (Speed field = 9). "Table 5-5. Speed Grade Maximum Frequency" of DM gives more details about frequencies associated with each speed grade.

    According to TRM and DM Speed field = 7 is not valid. I only assume that kernel sets your device to OPP_NOM as Speed field = 9 is the closest allowed value.

    Speed field = 7 might be because you use a pre-production DRA7xx sample.

    BR,

    Dobrin