[U-Boot] [resent] New chapter in i.MX51 datasheet an issue?

[Marek Vasut <marex@denx.de>]

Dear Stefano Babic,

> On 07/05/2012 09:11, David Jander wrote:
> > Dear Stefano,
> 
> Hi David,
> 
> > Yes, but is none of those boards using 3.15 or 3.3V? If they are, those
> > bits must be cleared!
> 
> This is a good question - also because SD was tested and it is working
> on these cards. I am asking to myself how it can work if voltage is wrong.
> 
> >> At the moment, we have no problems and I can explain why. The only
> >> boards setting these pins (for SD card) are mx51evk and vision2. Both
> >> are setting PAD_CTL_DRV_VOT_HIGH, and because the define is wrong, they
> >> are really setting the pin to low output voltage mode.
> > 
> > AFAIK, most SD-cards need 3.1V or more to work, and the EVK boots from an
> > SD card. That means, the rails NVCC_PER15 and/or NVCC_PER17 are probably
> > powered from a 3.15 or 3.3V supply, so the HVE bits for those pins must
> > be cleared in able to avoid damage (3.3V is what they call "Ultra High
> > Voltage").
> 
> Really I have expected that SD does not work if the voltage is lower as
> specified, not that theree is a damage - I can understand this in the
> opposite case (setting high voltage when low voltage is required).
> 
> >> For other boards and other pins, voltage is not explicitely set : this
> >> means they work in low voltage mode after a reset.
> > 
> > Everyone reading the documentation as it was available before 03-2012
> > would most probably think this is ok, even for 3.1...3.6V powered pins,
> > but according to the new documentation, it isn't. So probably many
> > boards need to be re-designed or at least u-boot board-code needs to be
> > fixed for them. This is a different issue though, and needs to be
> > addressed by the different BSP maintainers or board manufacturers.
> 
> I think only u-boot code should be fixed.
> 
> >> To fix arch/arm/include/asm/arch-mx5/iomux.h and synchronize it with the
> >> documentation, we need also to change mx51evk / vision2, setting the
> >> pins to PAD_CTL_DRV_VOT_LOW, and they will work as now.
> > 
> > ... and probably die.
> 
> well, they will work as now - with low voltage instead of high voltage.
> Anyway, I agree that this should be wrong, because when the code was
> written was thought that the voltage should be high.
> 
> > The setting is most probably wrong. All we need to do,
> > is change the define in the header files, and not touch the mx51evk /
> > vision2 BSP files. But the respective maintainers need to be warned
> > IMHO.
> 
> Go ahead in this direction. Then we can test on these boards (mx51evk /
> vision2 / efikamx), the only ones having these issue).

Respective maintainer just woke up ... just send me the efika patch, I should be 
able to test ;-)

> Best regards,
> Stefano Babic

Best regards,
Marek Vasut