Question, i.MX6Q initial values of Pad Control Registers

[Aemj]

Dear team,

I would like to ask about an initial value of Pad Control Registers of i.MX6Q.

My customer did read out some Pad Control Registers of i.MX6Q right after U-Boot startup on their own board.

And they found some values are not same as the initial values which are mentioned in your i.MX6Q reference manual after U-Boot startup.

For example;

- IOMUXC_SW_PAD_CTL_PAD_KEY_ROW4 register (address: 20E_05ECh) had the value of 1_30B0h and the initial value mentioned in RM is 1_B0B0h.

- IOMUXC_SW_PAD_CTL_PAD_NAND_CS1_B register (address: 20E_06D0h) had a value of 8B1h after eMMC boot, and the initial value mentioned in RM is 1_B0B0h. After SD boot, it is 1_B0B0h as mentioned in RM.

Could you show me why the values (which user read after boot-up) differ from the initial values mentioned in RM?

Can I understand that IROM code or u-boot may modify the values of those registers?

My customer designed their HW based on the initial values mentioned in RM.

If the initial values written in RM are not reliable, they have to re-design the HW.

Now they set the initial values into those registers in their custom U-Boot code as a temporary workaround.

Do you have any other ideas for a solutions of this?

Thanks,

Miyamoto

[gusarambula · Accepted solution]

Hello Miyamoto,

The values listed on the Reference Manual should be correct after the reset state. However, u-boot itself does change the value of several registers so it would make sense that you are seeing configurations different than the out-of-reset values.

It is a good practice to set all required registers as part of your boot process in order to make sure that your desired configuration is present. I would recommend to continue writing all necessary registers on your bootloader.

I hope this information helps!

Regards,