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

[Albin Tonnerre]

Hi Stephen,

On Mon, Aug 24, 2009 at 10:01:16PM -0400, Stephen Caudle wrote :
> I tried using your patches for the TNY-A9G20 on my QIL-A9G20 board from Calao. 

I guess you mean SBC35-A9G20?

> 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.

> 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?

Thanks for your feedback.
Regards,
-- 
Albin Tonnerre, Free Electrons
Kernel, drivers and embedded Linux development,
consulting, training and support.
http://free-electrons.com
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