[U-Boot] [PATCH v2] mxs: fixed battery boot on imx233-olinuxino-micro

[Marek Vasut]

On Wednesday, June 18, 2014 at 08:17:05 PM, Peter Schumann wrote:
> Am 17.06.2014 18:00, schrieb Stefano Babic:
> > Hi peter,
> > ...
> > On 17/06/2014 00:19, Marek Vasut wrote:
> > Agree. Reason is that this change is for all boards, and without a
> > proper testing I will avoid to merge it in the release.
> > 
> > Best regards,
> > Stefano Babic
> 
> Hi Stefano,
> 
> I've only the imx233 olimex board for testing. The DOUBLE_FETS switch in
> HW_POWER_MINPWR is some thing were maybe problems emerge.
> 
> I have very little load on the powerrails (imx233 + DRAM), so maybe with
> more current demand DOUBLE_FETS is working OK and even more may require
> it to be set.

If that was the case, the problem would manifest even when _not_ booting from 
battery-only supply, correct?

> The DOUBLE_FETS and HALF_FETS switches control the switching MOSFET size
> in the DCDC Converter. My assumption is that if we have a to big FET
> setting and to low current demand we trigger some failsafe mechanism.
> Because the required "on time" of the FET is smaller than the minimum
> possible "on time" of then DCDC FET control logic.
> 
> I don't have an easy way to test this assumption without an adjustable
> load.
> 
> The other change regarding mxs_power_enable_4p2() should be relatively
> safe to apply.

This breaks booting from battery on MX28 for some reason. The DC converter is 
not enabled at that point.

Best regards,
Marek Vasut