Cold start fail (-20) cause MXS NAND : DMA read error

[morrislai]

We test the long time cold start (-20 @ 10 hours),

First Power turn on :

the error shows "MXS NADA: DMA read error"

But Second Power turn on : workable

Is it NAND Flash problem or iMX6 UL issues ???

We use iMX6 UL SOM board for test.

[morrislai]

Dear Igor;

I use the SD card to boot , it is okay at -20, long time and no problem.

But I use the NAND Flash to boot, it is fail @ -20 and long time cold start.

1, Do you think that it is non-optimal driver issue or components hardware issue ???

2, The driver package is download from NXP web site.

[igorpadykov]

I think this may be due to non-optimal drive strength settings

of nand signals.

Best regards
igor

[morrislai]

Dear Igor;

Is it to adjust the setting of drive strength enable (DSE) ???

Or others ???

[igorpadykov]

Hi Morris

please try to check nand signals with oscilloscope

@ -20 and adjust drive strength accordingly.

Best regards
igor

[morrislai]

Dear Igor;

We check the Flash driver with 110 setting already, (It is the same with SD driver)

Should we increase or decrease the value at cold status ?? can you suggest me ??

[igorpadykov]

Hi Morris

most simple way, if cooling down the part causes more failures, then it is likely the drive strength is too high
causing more overshoots and undershoots. If heating up the part causes more failures, then the
drive strength is too low and the signals may not rise/fall fast enough.

Best regards
igor

[morrislai]

Dear Igor;

We try to adjust the DSE paremeter, it is helpful at -25C. But we try to cold start @-40C and @-30C long time, it is still fail and hart to turn on. Do you  have any suggestion ??? apreciate you.

[igorpadykov]

Hi Morris

one can try to reduce operating frequency.

If DSE change does not help, seems layout is not optimal.

Best regards
igor

[morrislai]

Dear Igor;

We try to adjust the CPU frequency to interactive mode, it can work at -30C but still fail at -40C.

Do you have any suggestion ????

morris lai

[igorpadykov]

Hi Morris

one can try to find more optimized for -40C ddr settings  :

https://community.freescale.com/docs/DOC-105652 

is ddr chip rated for -40C, also drive strength can be tweaked from

ddr side, using Extended Mode Register (EMR).

Best regards
igor

[morrislai]

Dear Igor;

But we try the SD card boot, it is okay at -40C. the fail is occured on Flash Memory type boot.

Does it related to DDR setting ???

morris lai

[igorpadykov]

Hi Morris

yes, many issues with only second successful boot are related to

ddr settings. It may be useful to check it too.

Also please check external crystal longer start-up times at colder temperatures,

try longer POR (up to several secs.) for test.

Best regards
igor

[morrislai]

Dear Igor;

I can see the CPU temperature at boot initial log. I try to turn on and turen turn off power for many times,

The CPU temperature will rise and the Boot will be successful at one temperature point,

Do you have any comment ?? I try to adjust many parameters without big improvement.

Maybe it is silicon issue ??? Because the SD Card Boot is okay.

[igorpadykov]

Hi Morris

when doing turn on and turn turn off power for many times,

please verify that board was fully powered off, so all board capacitors were discharged

to zero. Take period between turn on and turn turn off for 30sec. for example.

Best regards
igor

[morrislai]

The results is fail, This is my log, please help to check

[igorpadykov]

had you verified that all board capacitors were discharged

to zero before power-up . What is period between turn on and turn turn off.

As for i.MX6UL EVK nand, it is shared with eMMC and MicroSD, so its

routing have stubs and additional lines for eMMC and MicroSD and such routing

is not optimal and may prevent nand operation at low temperatures.

Please consider to make nand layout short as possible in custom board

layout. I am afraid i.MX6UL EVK was not tested at low temperatures, it is

reference design with purpose just to test as much peripherals as possible.

It was not designed to operate at very low temperatures.

Best regards
igor

[morrislai]

Dear Igor;

1, Our test SOM is NXP released iMX6 CPU Board, do you mean I need to modify the original layout ???

2, Which registers are related the operating frequency ???

Thanks for you answer

[igorpadykov]

Hi Morris

low temperature issues may be due to non-optimal drive strength settings

(drive strength increases with low temperature), so timings for NAND

and DDR may be violated. May be recommended to check NAND signals

with oscilloscope and run ddr test to find more optimized drive strength settings

https://community.freescale.com/docs/DOC-105652 

Best regards
igor
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