[Gta04-owner] New SD card setup

Neil Jerram neil at ossau.homelinux.net
Sat Sep 22 13:19:14 CEST 2012


"Dr. H. Nikolaus Schaller" <hns at goldelico.com> writes:

> Am 22.09.2012 um 11:13 schrieb Neil Jerram:
>
>> Hi all,
>> 
>> I'm about to setup a new SD card and am wondering about the detail of
>> the partitioning instructions.
>> 
>> The README at http://sourceforge.net/projects/qtmoko/files/GTA04/ says:
>> 
>>> * You need specially partitioned SD card. The partitioning is described
>>>  here: http://code.google.com/p/beagleboard/wiki/LinuxBootDiskFormat 
>> 
>> and that beagleboard link includes a section called "Set the Geometry of
>> the SD Card".
>> 
>> My question is whether that section really matters, and if so why.
>> IIRC, I followed it when setting up my last SD card, but then I found -
>> when printing the partition record again - that all those changes hadn't
>> stuck.  I.e. the numbers of heads, cylinders etc. had reverted back to
>> what they were initially.
>> 
>> Can someone explain whether and why those instructions are needed?
>
> This is because the Boot ROM within the OMAP3 can find and load the file
> "MLO" from the first FAT partition. Since the Boot ROM does not know anything
> about the FAT file system format it reads from a specific sector. Formatting
> the SD card in the given way makes sure that if you mount the SD card and
> write the first file, it will be stored at the correct location so that it *can* be found
> by the Boot ROM.
>
> You may not notice bad formatting unless you press the AUX button during
> boot because without pressing the button, the Boot ROM will fetch X-Loader
> and U-Boot from NAND and then U-Boot checks if there is a SD card and loads
> the kernel from there. And, if it does not find the MLO on the SD card, it
> will load it from NAND even if you did press the AUX button.
>
> So using this way of booting from SD card does not reveal an issue with
> the # of heads/cylinders etc. Unless you erase NAND.
>
> To summarize: if your X-Loader and U-Boot in NAND is ok, you don't have
> to format the SD card in any special way (except making at least two partitions).
> And you don't even have to store a "MLO" file on it.
>
> Hope this helps,
> Nikolaus

Many thanks for explaining that, Nikolaus.  I'll try it with the new SD
card and hope that it sticks this time.

Regards,
        Neil


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