[U-Boot] RTC value corruption on QIL-A9G20 startup

[Stephen Caudle]

Hi Albin,

On Tue, Aug 25, 2009 at 4:37 AM, Albin Tonnerre
<albin.tonnerre at free-electrons.com> wrote:
> I guess you mean SBC35-A9G20?

I actually tried it with the patches for both boards (TNY & SBC35) and
saw the same result.

> > Everything seems to work properly except the RTC.  They use the same M41T94
> > part and the CS is the same on both boards (PA3).  I can set the RTC using the
> > "date" command and read back the value okay.  However, when I power cycle the
> > board, the value is getting corrupted at startup due to some erroneous SPI
> > write.
> >
> > I don't believe the code you submitted is causing this problem because the RTC
> > is getting corrupted even if I compile out SPI and RTC support completely.  I
> > was just wondering if you have seen this problem on your board?
>
> Yes, I also experience this issue.

Well, at least I'm not the only one. :)

>
> > I probed the
> > CS line with an oscilloscope and I am definitely seeing it go low on U-Boot
> > startup for a short time, but the clock line seems to be floating.  I believe
> > the activation of the CS at startup is causing junk data to be written to the
> > RTC, which is corrupting it.  Any idea why this might be happenning?
>
> Currently, I don't really have any idea. Besides, it's going to be hard for me
> to debug this, as I don't have an oscilloscope at hand. Would you please try to
> run u-boot within a debugger to see where exactly the CS line is driven low?

I upgraded to the "next" branch and the problem seems to have gone away.  I will
continue to investigate the root cause of this and let you know what I find.

Regards,
Stephen