Stressapptest crashes immediately

[stefanovski]

Hello out there,

i'm facing a DDR3 problem on a custom design with i.MX6. I calibrated the DDR3 with DDR Stress Test (2.2.0).

Did the write leveling succesfully, the dqs gating succesfully as well as the read and write calibration.

The DDR stress tester runs without any errors. (Here are the calibration results)

  MMDC registers updated from calibration

   Write leveling calibration

   MMDC_MPWLDECTRL0 ch0 (0x021b080c) = 0x00150019

   MMDC_MPWLDECTRL1 ch0 (0x021b0810) = 0x0017000E

   MMDC_MPWLDECTRL0 ch1 (0x021b480c) = 0x00040019

   MMDC_MPWLDECTRL1 ch1 (0x021b4810) = 0x0012001B

   Read DQS Gating calibration

   MPDGCTRL0 PHY0 (0x021b083c) = 0x43200324

   MPDGCTRL1 PHY0 (0x021b0840) = 0x026C0268

   MPDGCTRL0 PHY1 (0x021b483c) = 0x43080314

   MPDGCTRL1 PHY1 (0x021b4840) = 0x03140268

   Read calibration

   MPRDDLCTL PHY0 (0x021b0848) = 0x40383438

   MPRDDLCTL PHY1 (0x021b4848) = 0x3C383442

   Write calibration

   MPWRDLCTL PHY0 (0x021b0850) = 0x342E3A34

   MPWRDLCTL PHY1 (0x021b4850) = 0x402E423A

Success: DDR calibration completed!!!

As soon as I boot into linux and run the stressapptest from google it crashes almost immediately.

Sometimes I get some miscompare results showing that the two least significant bytes are wrong.

But most of the time the application just crashes with different types of errors.

Has anyone any idea what is happening here ?

Thanx for your help

Norbert

[TheAdmiral]

All -

The effect of reducing the resistor value of the ZQ resistor is to increase the drive strength of all your signals.

240 Ohms is specified by the JEDEC standards as the corect resistor value.

I will admit that, for testing purposes only, I have reduced the ZQ resistor value a few times, usually on the DDR device side.

But the correct way to increase drive strength is to do this in the configuartion registers. If you have IOMUX registers set to DSE of '101' or '110', try increasing them up to maximum value: '111'. If that works, then you can selectively reduce drive strength until you achieve a setting you like. For the DDR devices, this is done in the mode registers.

NXP does not recommend using different ZQ resistor values than those stated in the device datasheet. For i.MX6 processors, this value is 240 Ohm 1% resistors. If a customer uses a different value, the customer assumes all risk.

A note about the DDR Stress test: We have been finding publically available stress tests that seem to push harder, and in different configurations than the DDR Stress test.  The stress test that NXP uses is provided "as is". We do work to evolving our stress test to be even more stressful for our internal use, but if you find something even more stressful in a particular operating system, by all means, use every tool available.

Cheers,

Mark

[Yuri]

Hello,

1.
   Please try to run FSL DDR Stress tool during long time (at least several hours).

2.

  Have You used the same DDR initalization setting as for DDR stress (after calibration) ?

Have a great day,
Yuri

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[stefanovski · Accepted solution]

Hello Yuri,

yes i ran the FSL DDR Stress tool for several hours and i used the settings i got from calibration.

Believe it or not, i fixed the problem by adjusting the ZQ resistor at the i.MX6 a little bit downwards

because i had the feeling that the impedances on my board do not match the 50 Ohm, 100 Ohm

good enough.

Now stressapptest is running without errors. I still can't understand how FSL DDR Stress tool and

memtester could'nt make out any errors while stressapptest crashed immediately. Mysterious.

[Yuri]

:smileyconfused: