Booting from eMMC at ethernet pins

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Booting from eMMC at ethernet pins

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AlfTeleco
Contributor III

Hello and thanks in advance, 

 

We are facing a booting problem. 

The IMX8MP's pins can be configured with several options. This configuration can be made by default HW reset, by the ROM at initialization or by .dtb/driver configuration. 

Default HW is the value that the rHW registers present at power on, its fixed and has nothing to do with SW

ROM initialization, are the settings that the IMX8 configure in its HW registers according, for instance, to its boot pins mode. It's also nothing to do with SW.

.dtb/driver configuration, it's done at SPL/Kernel level and has everything to do with SW. 

In the IMX8MP, when boot pins are set to boot from uSDHC3 it seems that ALT2 mode is set by the ROM as the default configuration. This mode, lets the IMX8 boot from an eMMC device present at the NAND pins. 

But uSDHC3 is also capable of booting from ethernet pins, thanks to pimux capabilities. To boot from an eMMC present at the ethernet pins IMX8 must be configured in ALT6 mode. 

The question is: 

Is it possible to achieve this before the uboot( SPL ) space? Is it possible to change the default ( ALT 2 ) mode to boot using ALT6 mode ( and run from an eMMC at the ethernet pins ) ?

Thank you very much!

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igorpadykov
NXP TechSupport
NXP TechSupport

Hi Alvaro

 

>But uSDHC3 is also capable of booting from ethernet pins, thanks to pimux capabilities.

>To boot from an eMMC present at the ethernet pins IMX8 must be configured in ALT6 mode.

 

sorry this is not correct. uSDHC3 is not capable of booting from ethernet pins, as pin muxing

is fixed in ROM.

 

>The question is:

>Is it possible to achieve this before the uboot( SPL ) space? Is it possible to change the default ( ALT 2 ) >mode to boot using ALT6 mode ( and run from an eMMC at the ethernet pins ) ?

 

in general one can use additional small ecspi boot loader which make necessary pin muxing before uboot.

 

Best regards
igor

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igorpadykov
NXP TechSupport
NXP TechSupport

Hi Alvaro

 

>But uSDHC3 is also capable of booting from ethernet pins, thanks to pimux capabilities.

>To boot from an eMMC present at the ethernet pins IMX8 must be configured in ALT6 mode.

 

sorry this is not correct. uSDHC3 is not capable of booting from ethernet pins, as pin muxing

is fixed in ROM.

 

>The question is:

>Is it possible to achieve this before the uboot( SPL ) space? Is it possible to change the default ( ALT 2 ) >mode to boot using ALT6 mode ( and run from an eMMC at the ethernet pins ) ?

 

in general one can use additional small ecspi boot loader which make necessary pin muxing before uboot.

 

Best regards
igor

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AlfTeleco
Contributor III

Okay Igor, and thank you! 

Just to be sure that I understand your reply please correct the next sentences if I am wrong: 

- Pinmux is seet by the ROM at boot process depending on bootpins or fuses. 

- When booting with the uSDHC3 option, ROM will implement the necessary pinmux to boot from NAND pins like in this table: 

AlfTeleco_0-1624434550810.png

- In order to modify the pinmux set by ROM, we MUST achieve an SPL ( uboot for instance ) in order to do so.

 

Thanks in advance

 

 

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igorpadykov
NXP TechSupport
NXP TechSupport

Hi Alvaro

 

yes your understanding is correct.

 

Best regards
igor

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