warning! HS400 strobe DLL status REF not lock!

[chaitanya_sonag]

Hi,

We have used imx8mq processor with our customized board.

Currently, we are facing issue related to HS400 mode of eMMC and lock frequency is 200MHz.

We are using 4.14.78 kernel with some customization changes.

Also, we have increased drive strength by decreasing resistance to 40 ohm from 65 ohm due to temperature range requirements.

After booting the board, we are having below warning in around half an hour.

sdhci-esdhc-imx 30b40000.usdhc: warning! HS400 strobe DLL status REF not lock!

I want to know the effects due to this warning and why this warning is coming?

And how to make strobe signal aligned with the clock frequency?

Please note that we have validated above things on imx8mq EVK but this issue is not occurred on that.

For more information, we have gone through this ticket HS400 strobe DLL status REF not lock! on eMMC  along with similar kind of tickets but all the patches have been integrated in the driver which is sdhci-esdhc-imx.c

Your immediate response is appreciated.

[igorpadykov]

Hi Chaitanya

since as you mentioned "have validated above things on imx8mq EVK but this

issue is not occurred on that", this may be related to hardware problems.

Please pay attention to emmc routing guidelines described in sect.3.6.8 High

speed signal routing recommendations

IMX6DQ6SDLHDG, Hardware Development Guide for i.MX 6Quad, 6Dual, 6DualLite, 6Solo Families of Applic...

Also board noise may affect not locking issues, suggest to check

sect.3.6. Power connectivity/routing i.MX8M Hardware Developer’s Guide

Best regards
igor
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[chaitanya_sonag]

Hi Igor,

We have verified all the High speed signal routing recommendations from the iMX6 HDG. Also incorporated all recommendations from iMX8 HDG.

Proper power plane & ground reference is provided for all high speed signals.

I have shared a link in my first post, the issue is resolved by adjusting delay related to Strobe signal. Can you direct us in that direction from firmware side?

[igorpadykov]

Hi Chaitanya

as you wrote:

"we have validated above things on imx8mq EVK but this issue is not occurred on that."

seems no additional firmware adjustments are needed.

Best regards
igor

[khushbu_patel]

Hi,

I found below patch would be helpful for the warniig!!

[11/14] mmc: sdhci-esdhc-imx: optimize the strobe dll setting - Patchwork  

This would increase the delay upto 50us and polling on the status register to check the REF and SLV lock status.

Hope this will helpful.

Regards,

Khushbu Patel