[U-Boot] [PATCH] mxs: fixed battery boot on imx233-olinuxino-micro

[Marek Vasut <marex@denx.de>]

On Wednesday, May 21, 2014 at 04:01:55 AM, Peter Schumann wrote:
> This patch makes it possible to boot from battery on olinuxino Boards
> from Olimex.
> 
> We should not set DOUBLE_FETS in HW_POWER_MINPWR

Please explain how you arrived to this conclusion.

> , it makes my system
> reset with in seconds while running on battery power.
>
> Also  mxs_power_enable_4p2() should not be called if running from
> battery. It switches VDDD and VDDA to LinReg mode and than turns off
> the VDDIO DCDC supply. At this point the system resets.

This has been tested on i.MX28 , can you please check what the differences are 
between these two chips and why it works only on one of them ?

> If we run on battery this is no good idea because the LinRegs are
> chained behind VDDIO and battery voltage seems not enough to power
> the system from LinRegs.
> Also is the power system already running on DCDC after BootROM hands
> over to u-boot, so no sense in switching back to LinRegs.

The BootROM never hands over to U-Boot, so this really makes no sense. Can you 
please explain ? The BootROM handles over to U-Boot SPL, which configures the 
power block.

Also, I find it a very bad idea to depend on the BootROM to actually start the 
DCDC converter. I don't think we can universally say the DCDC converter is 
running when entering U-Boot SPL. I also don't think we can even depend on the 
power block configuration when exiting the BootROM -- for example in JTAG Boot 
Mode, the BootROM halts early in the boot process and will likely not configure 
anything with regards to the power block.

[...]

THanks!

Best regards,
Marek Vasut