On 1/2/14, 7:41 AM, "Robert Nelson" <robertcnel...@gmail.com> wrote:
>> Hi,
>> Thank you for that clarification.
>> Does the boot modes (if altered) survive if the power is removed and
>> reapplied?
>
>Well they go back to factory default..
>
>This is why every "flashing" guide says pull the power.. As weird
>things happen when you "soft" reboot after flashing the eMMC...
>
>> The uEnv.txt is located in the boot partition, on both eMMC and uSD
>>card.
>> What line specifies in wich order to boot?
>
>In most cases it's more then just "one" line..
>
>>
>> I was wondering why the default is to first try eMMC even when an uSD
>>card
>> is detected.
>
>Because you are over thinking it. The bootrom is "simple" and it is
>setup to read the eMMC first.
>
>Here's the boot order:
>
>bootrom loads MLO from eMMC (if that fails it moves to microSD (hence
>dd if=/dev/zero to eMMC makes booting from microSD work..)
>MLO loads u-boot.img from eMMC
>u-boot.img first looks at microSD for uEnv.txt, reads that file in.
Hey Robert,
Now you have confused me and I thought I understood how the boot process
worked.
If the boot button isn¹t pressed, bootrom loads MLO from eMMC and this
loads u-boot from eMMC. I¹m unaware of bootrom loading MLO from SDCard if
MLO is missing from eMMC. Do you have a reference for this? Also, I¹m
unaware of MLO loading u-boot from SDCard if u-boot is missing from eMMC.
Do you have a reference for this? The only option to load from SDCard if
it exists is in the u-boot environment bootcmd which is here:
bootcmd=gpio set 53; i2c mw 0x24 1 0x3e; run findfdt; mmc dev 0; if mmc
rescan ;then echo micro SD card found;setenv mmcdev 0;else echo No micro
SD card found,
setting mmcdev to 1;setenv mmcdev 1;fi;setenv bootpart ${mmcdev}:2;mmc
dev ${mmcdev}; if mmc rescan; then gpio set 54; echo SD/MMC found on
device ${mmcdev};if
run loadbootenv; then echo Loaded environment from ${bootenv};run
importbootenv;fi;if test -n $uenvcmd; then echo Running uenvcmd ...;run
uenvcmd;fi;gpio set 5
5; if run loaduimage; then gpio set 56; run loadfdt;run mmcboot;fi;fi;
So mmcdev=0 if the SDCard is installed and mmcdev=1 if the SDCard in
missing, so bootpart=0:2 if the SDCard is installed and bootpart=1:2 if
the SDCard is missing. If the SDCard is installed, uEnv.txt is loaded from
the SDCard, which is where all the customization takes place.
What am I missing?
Regards,
John
>
>Regards,
>
>--
>Robert Nelson
>http://www.rcn-ee.com/
>
>--
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