Update: uMon is now booting from SD

Jarielle Catbagan jcatbagan93 at gmail.com
Sat Jul 4 15:23:51 UTC 2015

On Sat, Jul 4, 2015 at 6:50 AM, Ed Sutter <edsutterjr at gmail.com> wrote:
> On 7/3/2015 8:49 PM, Jarielle Catbagan wrote:
>> Hi Ed,
>> On Fri, Jul 3, 2015 at 6:03 AM, Ed Sutter <edsutterjr at gmail.com> wrote:
>>> On 7/2/2015 9:27 PM, Jarielle Catbagan wrote:
>>>> Hello Ed and all:
>>>> uMon is now booting from SD!
>>>> As Ed has indicated to me, the first reason why uMon did not appear to
>>>> boot from SD was that UART initialization was not performed when the
>>>> AM335x was booting from memory.  Originally, when uMon was booting
>>>> from UART, as Ed has mentioned to me, uMon was working and was able to
>>>> use the UART because it appears that the UART was set up already by
>>>> the internal ROM code during the UART boot procedure.
>>>> The UART initialization was suppose to be done in cpuio.c.  Ed has
>>>> sent me a diff containing the necessary modifications/additions that
>>>> has served as the basis for the UART initialization.  After applying
>>>> this diff to the current uMon tree, building the uMon image and
>>>> transferring the image to an SD card, attempting to boot from SD still
>>>> resulted in the BBB to appear to not boot up.
>>>> Ed has mentioned to me that one of the possible reasons why the SD
>>>> boot is not coming through could be something that is missing during
>>>> the UART initialization like clock management or power control.  This
>>>> has prompted me to go back and look through the AM335x TRM,
>>>> specifically on the sections regarding the PRCM (Power Reset Clock
>>>> Management) and UART modules.
>>>> It turned out that one of the UART0 registers, register MDR1, the
>>>> MODESELECT field had the value 0x07 which translates to the UART
>>>> module being disabled. Since the UART in uMon is already set up to
>>>> work with UART 16x mode, and the value for this mode is 0x00, this was
>>>> stored in the MODESELECT field of the MDR1 register.
>>>> After setting this field the uMon image was rebuilt, the GP header was
>>>> prepended to the image and was transferred to the SD card as "MLO".
>>>> Booting the SD card resulted in uMon being able to boot and to reach
>>>> the uMon command line.
>>>> My next steps before proceeding to finish DDR initialization is to
>>>> clean up the updated files that perform the necessary UART
>>>> initialization and then I will submit the patches that reflect these
>>>> changes for review.
>>>> _______________________________________________
>>>> umon-devel mailing list
>>>> umon-devel at rtems.org
>>>> http://lists.rtems.org/mailman/listinfo/umon-devel
>>> Congratulations!  Big step IMHO...
>> Thank you!
>>> This will allow you to experiment a bit more without the need to reboot
>>> manually each time.
>>> Looking forward to the patches!  I assume you used a FAT formatted SD
>>> card
>>> to do this?
>> Yes, I booted the uMon image from a FAT32 formatted SD card.
>>> Make sure you put everything in the port directory needed to reproduce
>>> this.
>>> When you submit the patches I'll push them and then whatever work I did
>>> that
>>> does not
>>> overlap with your patches I'll push up as well.
>>> Great stuff!!!  And excellent reporting!!!
>>> Ed
>> I just finished the patches and I sent them already to umon-devel for
>> your review.  Please let me know if there are any inconsistencies with
>> the patches and I'll be glad to make the necessary changes in order
>> for the patches to meet the specification that you are looking for.
>> Thanks!
>> Best Regards,
>> Jarielle
>> P.S. Have a great Independence Day weekend! :-)
> Jarielle,
> I didn't look at the patches yet, but I'm sure there won't be any
> inconsistencies.  The only
> point I was making with reference to me pushing some stuff in as well was to
> make sure
> that we have everything that's been done put into the port for use by folks
> in the future.

I agree.

> For example, I just happened to take the "raw" mode approach, so I want to
> make sure
> that is in the port, plus I did that LED/GPIO stuff so while its very
> trivial, its still more to
> go into the port for general use.
> Thanks for the patches!
> Ed

That's great to hear! Yeah, being able to boot using "raw" mode is a
nice option to have.  Integrating the LED/GPIO into the port would be
nice as well.  I think it would be cool to blink some LEDs for status
indication when uMon is running.  What do you think?

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