How to set VSW domain for "stm32mp151c" custom board as openstlinux dts (for using RETRAM)

[Machilus]

Hi All.

I want to use the battery to power the RETRAM so that the contents of the RETRAM can be preserved even if the board is not powered.

To do this, I connected the battery to the VBAT pin and set the "PWR_CR2_RREN" value to the "PWR_CR2" register of the M4 core firmware.

However, when booting from Linux, the value set in the "PWR_CR2" register disappears.

When booting in "Engineering Mode" and running only with the firmware of the M4 core, the setting value of the "PWR_CR2" register does not disappear even when the main power is turned off.

Is there anything I need to add when I create the "dts" file to enable that feature?

Please give me a lot of advice.

Thanks

Regards

Machilus

[mleo]

Hi @Machilus​ ,

You are right - the value of "PWR_CR2_RREN" should preserve the reset.

But in this case it's not device tree responsible. You need to modify the appropriate section of TF-A.

Best regards,

Milan

[Machilus]

Hi @mleo (ST Employee)

Thank you for your advice.

Can you give me detailed advice on which part of TF-A should be modified?

Or please send me a link to ST or wiki site that can be referred to for modification of TF-A.

I'll be waiting for your reply.

Thanks

Regards

Machilus

[BBeck.1]

Was there a link sent? I'm interested in this information as well.

Thanks,

Ben

[Machilus]

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