Testing EMMC fastboot mode on IMX8QX MEK

[komal_jpadia]

We would like to test various options from booting from EMMC on IMX8QX MEK:

1. EMMC fastboot mode

2. EMMC high speed

3. EMMC bus width selection.

From the Reference Manual (IMX8DQXPRM) section 5.8.2.1 (Boot Devices -> Expansion Device eFUSE configuration), I understand that the eFUSE needs to be programmed to select the above boot options. However, blowing eFUSE is a one time operation, which cannot be reverted.

I tried to use the 'fuse override' command from u-boot, but it fails with the message 'Override fuse to i.MX8 in u-boot is forbidden'. Also, as I understand, the override setting will be lost on reset. However, the boot mode testing can only be done by resetting the board, so the override will not be useful.

Is there a way to test the above modes without permanently programming eFUSE bits?

[lsanvictores]

Komal,

I am wondering if you did any benchmark testing after permanently setting the fuse.  I'm in the same situation, and I'd like to find out if you were able to provide any general results - maybe even percentages - before I proceed. 

Thanks for your time!

Lacy

[igorpadykov]

Hi Komal

your understanding is correct, eMMC fastboot can be activated only from fuse,

there is no way to test this mode without permanently programming efuses.

Best regards
igor
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[komal_jpadia]

Thanks Igor for your prompt reply.

So in that case, there is no way to change emmc rate and number of data lines for testing purpose only? Since these are also set in the eFUSE?

Also, since emmc fastboot cannot be tested without permanently setting the fuses, is there any experimental data available from NXP regarding boot performance of emmc fastboot vs emmc normal boot ? 

[igorpadykov]

Hi Komal

your understanding is correct. Unfortunately I am not aware

of boot performance of emmc fastboot vs emmc normal boot.

Best regards
igor