[U-Boot] PMIC initialization

[Lukasz Majewski <lukma@denx.de>]

Hi Jeroen van der Laan,

> Hi there,
> 
> I'm working on a board that is based on a i.Mx6soloX it has a
> PFUZE3000 PMIC the u-boot version we're using is 2016-03. The PMIC is
> by default configured with a voltage for our DRAM that is too low.
> We've discovered that this is an issue with some boards some of the
> time. The voltage is just below the bare minimum so I think the board
> has no big issue most of the time.
> 
> I want to adjust the voltage in u-boot in time for the board bring
> up. I'm afraid that a lot of issues will disappear but our tests will
> not cover if the initialization is too late. I want to be absolutely
> certain that it happens on time before the memory initialization.
> 
> what is the place to do this?
> Should I use an SPL bootloader?

You shall do it just before the DRAM init (and of course wait for some
time so the voltage can stabilize).

You don't need to use the PMIC DM/framework, just communicate with I2C
and change the values of registers of pfuze.

> Is power_init_board soon enough, or does code in this place require
> RAM? Are there any other options?

I think that board_early_init is a good place for this, but u-boot
2016.03 differs considerably from what we have now as massive DM/DTS
conversion is going on.

> 
> Best regards,
> Jeroen van der Laan
> 
> 
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Best regards,

Lukasz Majewski

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