Boot mode in IMX8M

[jemish_1990]

Hi All,

We are going to make product based on IMX8MQ (MIMX8MQ6DVAJZAA) processor.  Currently we are doing POC on IMX8MQ processor EVK.

• While understanding booting process from Technical Reference Manual we understand that if boot process failed to boot from configured device it will jump to boot from USB serial mode. There is NOTE in Technical Reference Manual regarding this:
• NOTE
  Before going into USB serial mode, Boot ROM detect
  SD/MMC card on USDHC1 port. If a card is inserted, ROM
  will try to boot from it. This is the so-called Manufacture
  SD/MMC boot. This feature can be disabled by blowing fuse
  “Disable SD/MMC Manufacture Mode”. 

• In IMX8MQ EVK there is an eMMC connected  to USDHC1. There is SD card connected to USDHC2. 

• We prepared bootable SD card.  We set SD boot mode and board get booted from SD which is correct. Then we clear eMMC boot partition using following command:

        echo 0 > /sys/block/mmcblk0boot0/force_ro
         dd if=/dev/zero of=/dev/mmcblk0boot0

• We set eMMC boot mode. Now as per technical reference manual board should not get booted because there nothing in boot partition of eMMC (USDHC1). But surprisingly it start booting from inserted SD card (USHDC2). Which is strange and incorrect!!!
• If we flash eMMC boot partition --> set eMMC boot mode --> boot from eMMC it works fine. Which correct.
• But there is one more interesting observation. If we SD boot mode -->remove SD card -->power on board.
• As per Technical Reference Manual it should jump to USB serial mode and before that is should go to USDHC1 interface (eMMC)  and boot from there. But here nothing is happening.
• Boot behavior is contradicting from description in Technical Reference Manual.

Has anyone observe such behavior? Is there in correction needed in Technical Reference Manual description?

Any suggestions or inputs are appreciated. As this is critical stage before we proceed ahead.

Thanks,

Jemish

[IlanHa]

Hi Diego,

Any update on this discussion? Any conclusion?

Thanks,

Ilan

[rmack1]

Diego:

I am having basically the same issue with a B4 board. If I install a Linux rootfs on an SD card (using the MfgTool2) and leave the SD card installed, I cannot get to the serial boot loader irrespective of the switches. It just boots Linux from the card. If I remove the SD card, it goes back to doing serial boot if set to 01/XXXX and MMC boot if set to 10/0010.

Ray

[rmack1]

I am digging through *massive* amounts of documentation. To date I have found the following in exactly one place:

If the SD card with bootable image is plugged in SD2, because of the MFG boot on SD2,
it will not enter the serial download mode.

The text above is on page 27 of i.MX Linux User's Guide so this is obviously a "feature" that got documented. I guess we would request that this same wording show up in the i.MX8MQ EVK Quick Start Guide and the i.MX8 EVK User's Manual.

It might also help to have someone who speaks English as a first language clean up the wording. The phrase "because of the MFG boot on SD2"  does not make any sense.

I suspect what is meant is: "The internal boot ROM system goes into a factory boot mode if a device is detected on SD2 and whatever image (including a valid customer image) will be booted irrespective of the settings of any of the boot pins. This behavior is intended for Manufacturing override of eMMC images, but also allows for a customer SD card to override the eMMC image." 

If this is correct, please feel free to spread those words at will!

Thanks.

Ray

[diegoadrian]

Hello,

How do you have configured the boot switches?

Please, be completely sure that you have the boot mode as mmc instead of sd.

Best Regards,

Diego.

[jemish_1990]

Hi Diego,

Sorry for late reply! Was on vacation due to Christmas Holidays.

Regarding you question for boot mode settings : We are using IMX8 EVM in which there two switches provided. We are using following settings:

Booting from SD on i.MX 8MQuad EVK
==================================
SWitch    D1  D2  D3  D4
SW801 :  1    1     0     0
SW802 :  1  0   (Internal boot mode)

Booting from eMMC on i.MX 8MQuad EVK
====================================
SWitch    D1  D2  D3  D4
SW801 :  0     0    1     0

Do you have any suggestions/inputs?

Thanks,

Jemish

[diegoadrian]

Do you know the revision of your board?

I have the understanding that are some boards that have the same behavior that you are mentioning.

Best Regards,

Diego.

[jemish_1990]

Hi Diego,

On the back side of he board I see that  it is "SCH-29615 REV B3".

Let me know if this information is enough to know board revision of do you need anything else.

Thanks,

Jemish

[diegoadrian]

Hello,

I apologize for the delay.

You have the same revision as my board and I experience the same problem, let me verify if this is a known problem and if there is already an errata about this.

Best Regards,

Diego.

[jemish_1990]

Hi Diego,

Please confirm weather it is issue with particular revision of EVK boards? Or is it issue with particular part number of IMX8MQ processor.

If it issue with particular EVK board let us know which revision of EVK boards has correct behavior as per Technical Reference Manual. Because we are planning to purchase three more EVKs.

Thanks,

Jemish

[diegoadrian]

Hello,

I am still reviewing this internally, they are trying to find what is the root cause. I will update you as soon as there is an answer.

Best regards,

Diego.

[jemish_1990]

Hi Diego,

Any update on this discussion? Any conclusion?

Thanks,

Jemish

[esben-e]

Hi Jemish

We are facing a similar problem with a custom  iMX8M board. Did you find a solution or a reason for the behavior you are describing above?

BR

Esben Elfving