How to see the current value of phyVref in DFI?

[george]

Hi all,

Our i.MX8M prototype board sometimes freezes unexpectedly.

And we are checking the configuration parameters for LPDDR4.

Please tell me about phyVref.

According to the description in RPA, phyVref is updated during data training.

We added a (attached) command in u-boot to read registers in DFI using "helper.c\imx8m\ddr\drivers - uboot-imx - i.MX U-Boot" as a reference.

Fortunately, the command seems to work correctly.

However, we always see the same value as the phyVref value set in RPA.

*We read 0x54006 in DFI as the address for phyVref.

Can we see the updated phyVref?

Best Regards,

George

[Yuri]

Hello,

  According to section 4.2 (Run DDR Calibration and generate DDR initial code) of

"MSCALE_DDR_Tool_User_Guide.pdf" from i.MX8 MSCALE SERIES DDR Tool Release (V2.10) :

   If DDR calibration failed, customers can try to modify some DDR parameters in the scripts,

including PhyVref. So, the RPA provides recommended PhyVref value, which generally can be modified

by customers in case of calibration fails.

Regards,

Yuri.

[george]

Dear YuriMuhin_ng‌,

Oh !!

Thank you for your reply.

Is my understanding below correct?

1) In other words, if calibration does not fail, phyVref can be anything.

    *Is phyVref the start value for calibration?

2) We can't get updated phyVref after calibration

Best Regards,

George

[Yuri · Accepted solution]

Hello,

  generally Your understanding is correct.

Note,  the relation between the Vref and PhyVref value is as follows:

Vref = VDDQ*PhyVref/128

If the initial value is applied:

Vref = 1100*0x11/128 = 146.1 mV

Note that this setting affects only Vref for the reads.

Regards,

Yuri.

[george]

Dear YuriMuhin_ng‌,

Thank you for your reply.

Please tell me one last thing.

> Vref = 1100*0x11/128 = 146.1 mV

Is this “1.1V” the voltage at the DDR_VREF pin?

Best Regards,

George

[Yuri]

Hello,

  1.1V is NVCC_DRAM(_1V1).

Regards,

Yuri.

[george]

Dear Yuri,

Sorry, I was confused.

Thanks,

George