NXP drivers: flash: soc_flash_mcux: CMD_MARGIN_CHECK fails infrequently

[DerekSnell]

On LPC5500 devices, using CMD_MARGIN_CHECK in the is_area_readable() can return with an error code, even when the flash is readable and operating as expected. The CMD_MARGIN_CHECK should be removed from is_area_readable() in this driver.

From the LPC55S69 datasheet: "As cells age and lose charge, a correctly programmed address will fail this check, while still being able to be read successfully for the remaining duration of the data retention time."

Replicating the issue can be challenging, as the CMD_MARGIN_CHECK returns errors on a small percentage of devices, or after a flash sector has been erased/programmed many times. But these errors have been seen on custom boards with the LPC55S69.

[bravl]

Hi @DerekSnell,

Could you share the part / page of the LPC55S69 datasheet you mention? I'm currently using an LPC55S69 device where I see the issue described here and would love to have a better understanding of why this occurs.

Thanks!

[DerekSnell]

Hi @bravl ,
I see this statement was removed from the datasheet. I also see that NXP has defeatured the CMD_MARGIN_CHECK. That command is not intended for the application level, it is an internal test used by NXP. The references to CMD_MARGIN_CHECK will also be removed from the User Manuals.

Best regards

[bravl]

Hi @DerekSnell,

Thanks for your response! Just a small extra question, is there any reason for "concern" that this check fails on relatively new chips? The boards we've seen it on are only a couple of months old and the part of the flash that reports the error has only been written once.

Bram

[DerekSnell]

Hi @bravl ,
No concern needed. This command can return false errors on perfectly good flash. That is the reason the command is defeatured from applications, and removed from this driver.

You can sleep easy, my friend :) Best regards

[bravl]

Hi @DerekSnell

Awesome, thank you for the explanation!

Bram