Update: uMon is now booting from SD

Jarielle Catbagan jcatbagan93 at gmail.com
Sun Jul 5 02:42:36 UTC 2015

On Sat, Jul 4, 2015 at 6:02 PM, Ed Sutter <edsutterjr at gmail.com> wrote:
> On 7/4/2015 2:29 PM, Jarielle Catbagan wrote:
>> Great to hear that it's working now!
> Yep,  I will go ahead and push the patches as they are (since I was able to
> verify the build), but we still need some documentation or a script on the
> procedure for building the SD card.

I agree, I'll most likely do a combination of a documentation and a
script.to take care of the SD preparation.  I'll work it out and I'll
send it over to you for review once I have it ready.

>> For the "raw" mode, a Configuration Header TOC Structure had to be
>> prepended before the GP header, am I right?
> Right, and that is placed at the base of the SD card (or at one of a few
> offsets)
> just using 'dd'.  I can add that if you want me to.
>> What are the other tasks that you would recommend I pursue.  I am
>> thinking of getting the DDR initialization working and then Ethernet.
>> What are your thoughts?
> Definitely DDR init should be next on the list.  After that, Ethernet is a
> good candidate,
> however one other more fundamental interface is MMC.  Think about the actual
> bootup of a full-blown bootmonitor that is then capable of loading an RTEMS
> application...

I see what you mean.  Yeah, the ultimate and ideal goal is to be able
to boot from the onboard memory which makes getting the MMC interface
working one of the main tasks along with DDR init.

> First of all, we're building the "MLO" as they call it.  As we know, that
> image is pulled from
> SD (or EMMC) directly into SRAM.  This is the first stage, and I think we're
> almost there.
> Next, the program needs to initialize DDR and then load the FULL uMon into
> DDR.  To do that
> the MLO needs to be able to read from the SD card.  So it seems to me that
> the MMC interface
> to the SD card is really the next most important interface to tackle.
> Lets think about this a bit.  Obviously both interfaces are needed; but my
> personal opinion is
> that the ability to read from MMC is more fundamental.  Actually, a
> functional BBB boot
> monitor *could* run without Ethernet as long as it had the ability to load
> from SD.
> Let me know what you think...

I am with you on that, both interfaces are very important.

I was actually looking into DDR init for a while now by using AM335x
TRM and http://processors.wiki.ti.com/index.php/AM335x_EMIF_Configuration_tips
and http://processors.wiki.ti.com/index.php/AM335x_DDR_PHY_register_configuration_for_DDR3_using_Software_Leveling
for references, and I honestly feel like I can get the DDR init
working first.  Nonetheless, I'll start looking into the MMC interface
simulataneously as well so that I can also start working on the MMC
initialization as soon as possible.

Thank you for your advice.  I'll get started.

> Ed
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