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AM6442: Refresh Rate Setting of LPDDR4/DDR4 in PSDK Linux

Hideaki Matsumoto
Expert 8350 points
Part Number: AM6442

Hi,

 

My customer wants to know the LPDDR4/DDR4 refresh rate on Linux SDK. Could you please answer the following their questions ?

Q1.  Is it a fixed value or does it vary depending on the temperature?

Q2.  If it is a fixed value, what is it ? where can they check it ?

Q3.  If it is different each version of silicon or SDK, please let them know that.

Please answer at least Q1 as soon as possible today in advance if it is difficult to answer all of above questions soon.

They found the part for directly writing registers to the DDR controller in the device tree, but they cannot confirm if it is overwritten by other part somewhere.

Also, they found the following thread on E2E.

https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1249674/am625-exact-bit-position-of-refresh-rate-inside-ddr16ss_denali_ctl_77

There is the following comment on this thread.

  • I've been told the dynamic refresh rate feature should be added towards the end of this year.

 Will the dynamic refresh rate feature be added in the next version 9.1 of Processor SDK Linux for AM64x ? If so, what’s the schedule ?

 

Thanks and regards,

Hideaki

  • +1
    TI__Guru 73750 points

    Hideaki, 

    Q1.  It is a fixed value.  DDR4 does have a feature called Temperature Controlled Refresh which is enabled when the temperature selected in the DDR Register Config tool is set above 85C.  LPDDR4 has an on-chip temp sensor which can be read to dynamically change the refresh rate based on temperature, but this is not currently implemented in the SDK.   

    Q2.  The value can be found in the tREFIab parameter in the DDR Register tool.  This value will automatically change if you change the temperature in the tool.  The user can override this value and enter their own value if needed.  From a register perspective, the refresh rate is reflected in TREF_F2 for LPDDR4, and TREF_F0 for DDR4

    Q3. It won't be different between silicon revisions or SDK.  It is based on operating temperature.  For example, for LPDDR4, it is 3.9us when operating below 85C

    I don't know the status of the feature to be added into the SDK.  i will have to find out.

    Regards,

    James