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

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

[Stephen Caudle]

Hello Albin,

I tried using your patches for the TNY-A9G20 on my QIL-A9G20 board from
Calao.  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?  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?

Regards,
Stephen

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

[Eric Bénard]

Hi,

Albin Tonnerre a ?crit :
> 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?

isn't the RTC connected to the SPI chip select that the internal 
firmware toggle on boot to probe for a SPI Flash ?

Eric

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

[Stephen Caudle]

Hello Eric,

On Tue, Aug 25, 2009 at 5:38 AM, Eric B?nard<eric@eukrea.com> wrote:
> isn't the RTC connected to the SPI chip select that the internal firmware
> toggle on boot to probe for a SPI Flash ?

That is certainly possible.  This problem went away for me when I upgraded to
the "next" branch.  Could the SPI dataflash code have been removed between
v2009.06 and "next"?  I'll look into this some more.  Thanks for the hint!

Regards,
Stephen

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

[Albin Tonnerre]

On Tue, Aug 25, 2009 at 08:51:56AM -0400, Stephen Caudle wrote :
> Hello Eric,
> 
> On Tue, Aug 25, 2009 at 5:38 AM, Eric B?nard<eric@eukrea.com> wrote:
> > isn't the RTC connected to the SPI chip select that the internal firmware
> > toggle on boot to probe for a SPI Flash ?
> 
> That is certainly possible.  This problem went away for me when I upgraded to
> the "next" branch.  Could the SPI dataflash code have been removed between
> v2009.06 and "next"?  I'll look into this some more.  Thanks for the hint!

Using the "next" branch doesn't help here. Anyway, the code Eric is referring to
is the firmware code the CPU executes from its internal ROM very early in the
boot process, so you likely won't find anything remotely related to this in
U-Boot.

Regards,
-- 
Albin Tonnerre, Free Electrons
Kernel, drivers and embedded Linux development,
consulting, training and support.
http://free-electrons.com
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[U-Boot] RTC value corruption on QIL-A9G20 startup

[William C. Landolina]

> -----Original Message-----
> From: u-boot-bounces at lists.denx.de [mailto:u-boot-bounces at lists.denx.de] On Behalf Of Albin Tonnerre
> Sent: Tuesday, August 25, 2009 12:49 PM
> To: u-boot at lists.denx.de
> Subject: Re: [U-Boot] RTC value corruption on QIL-A9G20 startup
>
> On Tue, Aug 25, 2009 at 08:51:56AM -0400, Stephen Caudle wrote :
> > Hello Eric,
> > 
> > On Tue, Aug 25, 2009 at 5:38 AM, Eric B?nard<eric@eukrea.com> wrote:
> > > isn't the RTC connected to the SPI chip select that the internal 
> > > firmware toggle on boot to probe for a SPI Flash ?
> > 
> > That is certainly possible.  This problem went away for me when I >
> > upgraded to the "next" branch.  Could the SPI dataflash code have been 
> > removed between
> > v2009.06 and "next"?  I'll look into this some more.  Thanks for the hint!
>
> Using the "next" branch doesn't help here. Anyway, the code Eric is referring to is the firmware code the CPU > executes from its internal ROM very early in the boot process, so you likely won't find anything remotely related to > this in U-Boot.
>
> Regards,
> --
> Albin Tonnerre, Free Electrons
> Kernel, drivers and embedded Linux development, consulting, training and support.
> http://free-electrons.com

Has there been any resolution on this?  From what I can see (with scope and logic analyzer) the RTC seems to be corrupted by the DataFlash boot code built into the chip.  [The Calao board doesn't have the DataFlash memory and used the chip select for its RTC instead...]

Has anyone found a smoking gun inside U-Boot or will we have to wait for Calao to make boards with the RTC on a different chip select?

Thanks,
Bill Landolina
Technology Atlanta Corporation
500 Sugar Mill Road, Suite 202A
Atlanta, GA 30350

(404) 303-0446 (Voice)
(404) 303-0448 (FAX)
(678) 596-3625 (Cell)
wcl at techatl.com

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

[Eric Bénard]

Hi Willian,

William C. Landolina a ?crit :
> Has there been any resolution on this?  From what I can see (with
> scope and logic analyzer) the RTC seems to be corrupted by the
> DataFlash boot code built into the chip.  [The Calao board doesn't
> have the DataFlash memory and used the chip select for its RTC
> instead...]
> 
> Has anyone found a smoking gun inside U-Boot or will we have to wait
> for Calao to make boards with the RTC on a different chip select?
> 
u-boot is executed after the bootrom so there is nothing to do on the
software point of view. You can connect a RTC on the I2C ...

Eric

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

[Stephen Caudle]

On Thu, Aug 27, 2009 at 1:48 PM, William C. Landolina<wcl@techatl.com> wrote:
> Has there been any resolution on this? ?From what I can see (with scope and logic analyzer) the RTC seems to be corrupted by the DataFlash boot code built into the chip. ?[The Calao board doesn't have the DataFlash memory and used the chip select for its RTC instead...]

No resolution here.  I am still seeing the problem (even on the next
branch).  This definitely seems to be caused by the processor boot
ROM.

> Has anyone found a smoking gun inside U-Boot or will we have to wait for Calao to make boards with the RTC on a different chip select?

I believe a hardware change is the only way to fix this problem.

Regards,
Stephen

[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@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