[U-Boot] [PATCH] mx23: Put back RAM voltage level to its original value

[Marek Vasut <marex@denx.de>]

Dear Fabio Estevam,

> On Fri, Apr 26, 2013 at 3:16 PM, Marek Vasut <marex@denx.de> wrote:
> > http://s8.postimg.org/dn7jhntut/imx233_olinuxino_maxi_2_5_V_rising.jpg
> > check this, this is as much as I got from tsvetan so far, it's the
> > VDDMEM ramping. I dunno what's that weird drop before it starts going
> > from 1V5 to 2V5, but it's strange at best and I don't like it. I think
> > that's also the source of our problems, the DRAM suffers undervolt and
> > quickly afterwards is configured for regular operation ... I'd say check
> > mx23_mem_setup_vddmem() and inspect the
> 
> Currently mx23_mem_setup_vddmem() does not clear ENABLE_ILIMIT
> bit as recommended by the mx23 Reference Manual:
> 
> "Controls the inrush limit (~10mA) for the memory
> supply voltage. Default is active. This should remain
> active until the supply settles after enabling the linreg.
> This should be disabled before accessing the memory."
> 
> FSL bootlets does clear this bit.
> 
> I did the same as FSL bootlets locally and this alone does not allowed
> me to boot the kernel without bumping VDDMEM to 2.6V.
> 
> I can send a patch that clears ENABLE_LIMIT, after this one gets applied.

Fabio, can you get someone in FSL to measure all these VDDx (VDDD, VDDA, VDDIO, 
VDDMEM) rails with stock 2013.04 U-Boot image from powerup to u-boot command 
line and send us the results? You'd need a scope that can produce an image of 
what's happening on the rails. I just can't figure out how to get this displayed 
on my scope, sorry :-(

Best regards,
Marek Vasut