Can't boot from sd-card on BeagleBone Black

Discussion about U-Boot and the kernel.
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Re: Can't boot from sd-card on BeagleBone Black

Postby Pavel47 » Mon Aug 31, 2020 9:59 am

$this->bbcode_second_pass_quote('', 'P')roblem is your questions are now getting very technical.

You mean my question "Is it possible to boot without having kernel on sd-card ?"
or, if you prefer
"Is it possible to only execute 3 phases of bootloader (phase 1: ROM code; phase 2: secondary program loader (MLO); phase 3: Tertiary Program Loader (u-boot.img) and that stop at bootloader prompt (i.e. U-Boot#) ?
Is this question very technical ?

$this->bbcode_second_pass_quote('', 'N')ow if you want 2017 uboot behavior, you could just download that source, and use it - but where is this going.

I've already tried it. Unfortunately my crosstoolchain fails to build v2017 branch ... it gets errors which I don't understand (I used configuration from 2017).
On the other side, with master branch of u-boot, there is no problem: u-boot is built well with different configurations.

$this->bbcode_second_pass_quote('', 'M')aybe its school homework, but if so you will already get a good mark, so don't stress.

No, I'm not scholar. I want to have u-boot environment and explore it ... e.g. execute the commands like:
U-Boot# read 82000000 400000 200000
U-Boot# mmc rescan
U-Boot# mmc 0:1 82000000 uimage
U-Boot# 82000000 uImage
etc.

$this->bbcode_second_pass_quote('', 'F')or me, uboot in this case is doing what it should be doing, so what we are doing is is just chatting round the subject, and noone really benefits.

Why what was possible in 2017, no longer possible in 2020?
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Re: Can't boot from sd-card on BeagleBone Black

Postby summers » Mon Aug 31, 2020 11:31 am

For that functionally just interrupt uboot when it comes up. You usually have a few seconds to hit "space" or something similar, and if you do *all* uboot versions will drop you to a prompt on the uart. Thats far easier to do than what has been discussed so far.
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Re: Can't boot from sd-card on BeagleBone Black

Postby Pavel47 » Mon Aug 31, 2020 12:25 pm

So, you can't provide answer (YES/NO) to the question:
"Is it possible to run just 3 phases of the bootloader, then stop at the bootloader prompt (i.e. stop at U-Boot # ... without kernel loading) ?

$this->bbcode_second_pass_quote('', 'Y')ou usually have a few seconds to hit "space" or something similar, ...

I have no keyboard on BBB.

$this->bbcode_second_pass_quote('', 'T')hats far easier to do than what has been discussed so far.

According to Chris Simmonds it's quite easy ... at least it was easy in 2017.
Please have a look at his approach. Here is extract from his book:
https://drive.google.com/file/d/1TQWy3jYVvUr4dmQDUjmJghELRV5pa1HK/view?usp=sharing
So what was easy in 2017 became complicated in 2020 ?
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Re: Can't boot from sd-card on BeagleBone Black

Postby summers » Mon Aug 31, 2020 1:47 pm

Sigh
$this->bbcode_second_pass_quote('', 'S')o, you can't provide answer (YES/NO) to the question:
"Is it possible to run just 3 phases of the bootloader, then stop at the bootloader prompt (i.e. stop at U-Boot # ... without kernel loading) ?

1) attach a 3.3V UART to serial connector to the UART pins on the BBB
2) attach the serial connector to another computer
3) set a terminal on that computer to connect to the serial port
4) switch on the BBB
5) immediately on the other computer hit space bar
6) uboot on the BBB is interrupted, and drops to the uboot prompt
7) type commands to you hearts content

So yes on *all* version of uboot, its possible to interrupt it.

This is what was written above, in less detail. If you need all this detail, its clear you don't understand how these arm embedded board work, and how uboot has been so good. uboot brings up minimal of what it can, e.g. the memory controllers, and the cpu, and a uart. This is why communication to the uart is important.
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Re: Can't boot from sd-card on BeagleBone Black

Postby Pavel47 » Mon Aug 31, 2020 6:10 pm

Until 7) I've already reported in my previous mails (except I didn't hit space bar on host).

$this->bbcode_second_pass_quote('', 'I')f you need all this detail, its clear you don't understand how these arm embedded board work, and how uboot has been so good.

Probably ... that's why I posted my question here.

$this->bbcode_second_pass_quote('', 'u')boot brings up minimal of what it can, e.g. the memory controllers, and the cpu, and a uart. This is why communication to the uart is important.

Can you just suggest what I need to do (in terms of formatting the SD card ... or its contents) to get the U-boot prompt at the end.
In my previous mail I provided a uart communication log (only the top half, but I can provide the rest).
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