[U-Boot] Automatic firmware upgrade using USB DFU

[Lukasz Majewski]

Hi Tamás,

> Dear All,
> 
> I am trying to implement an automatic firmware upgrade functionality
> on a U-Boot / embedded Linux board the following way. If anyone has
> done something similar before, please, comment if this is the right
> approach to the problem or I should choose a different solution? The
> hardware is a BeagleBone Black acting as the DFU device (to be
> updated). It is connected to a host machine (PC) that downloads the
> new firmware using USB DFU.
> 
> 
> So, here are my planned steps for DFU fw upgrade.
> 
> 1) A U-Boot environment variable is set from embedded Linux if a fw 
> upgrade is required. 

I suppose that you have already managed to modify the u-boot envs. When
I was extracting the envs to restore them, I've found following script
very useful.

cp `find . -name "env_common.o"` copy_env_common.o
objcopy -O binary --only-section=.rodata.default_environment `find .
-name "copy_env_common.o"` tr '\0' '\n' < copy_env_common.o >
default_envs.txt

Here you can modify default_envs.txt

mkenvimage -s 4096 -o params.bin default_envs.txt
rm copy_env_common.o default_envs.txt

params.bin should be stored on the medium.


> Then the board is rebooted.
> 
> 2) In the boot-up script, U-Boot checks the value of the environment 
> variable and enters DFU mode instead of booting the Linux kernel.
> This command is executed to enter DFU mode: 'dfu 0 mmc 0'.
> 
> 3) At this point the host recognises the DFU device and downloads the 
> new firmware image.
> 
> 4) After the download has finished,

Here since we are polling we need to either press ctrl+C or specify -R
with dfu-util command. The problem with -R is that we will reset
without executing any commands, so the env will not be reset.

Workaround (as I use it in our boards) is to perform 
dfu-util -R -aX -D params.bin as the last command.

What presumably you are requiring is to be able to perform:
setenv UPDATE "1"; dfu-util -aX -D file1; dfu-util -aX -D file2; setenv
UPDATE "0"; reset;

For now I can only propose the above workaround.

However, up till now we are only supporting -R switch, but in the
dfu-util (version 0.7) there is the -e/--detach option.

I will investigate if we could use dfu-util -e from host to replace
pressing ctrl+C after flashing the device.

>  the environment variable is reset 
> to indicate normal boot and the board is rebooted.
> 
> 5) Board boots up using the new firmware.
> 
> 
> When tested this manually, I found a problem in step 4) because
> U-Boot requires pressing Ctrl+C after the download finished. This
> suggests me that DFU can't be controlled by a script as I described
> above. Is this correct? 
> What is the idea behind waiting for Ctrl+C
> and not returning immediately? 

In the u-boot UDC/gadget is polled and hence we must either specify -R
switch at dfu-util or press ctrl-c to end USB transmission and return
to target's prompt.

> Any comments or hints are appreciated.
> 
> Thanks,
> -Tamás
> 
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-- 
Best regards,

Lukasz Majewski

Samsung R&D Institute Poland (SRPOL) | Linux Platform Group