Bare metal images via mfgtool/imx_usb_loader

[hjalfi]

I see from this thread:

https://www.mobileread.com/forums/sho....php?p=2185626

...that some people were working on running writing custom images which get deployed via mfgtool of imx_usb_loader, for experimenting with various aspects of the system.

Did anyone ever get one of these doing anything at all interesting, and if so, is the source available? For example: drawing something on to the screen, although I'd be happy enough just making the LED blink.

I know I can also go and start dissecting u-boot, but it would save time if someone had already done one.

[knc1]

Originally Posted by hjalfi

I see from this thread:

https://www.mobileread.com/forums/sho....php?p=2185626

...that some people were working on running writing custom images which get deployed via mfgtool of imx_usb_loader, for experimenting with various aspects of the system.

Did anyone ever get one of these doing anything at all interesting, and if so, is the source available? For example: drawing something on to the screen, although I'd be happy enough just making the LED blink.

I know I can also go and start dissecting u-boot, but it would save time if someone had already done one.

I was hoping that someone with a better memory than mine would tackle this one -

I only recall two -
An alternate u-boot that includes fastboot.
An alternate kernel that includes kexec support.

Both system level customizations, not the user-land customizations you seem to be asking about.

[hjalfi]

Actually, I *am* looking for system level customisations; I want to use USB downloader mode to drop a binary into memory and jump to it, so that the binary runs without any OS. (I have a background in embedded systems so am used to this.)

I'm looking for a simple starting point simply to avoid the long and tedious process of trying to figure out from the u-boot code how to initialise DRAM, set up the serial port, etc.

You mention the kernel --- I did see a reference to a kexec-capable kernel, but it was intended to get written to flash and then be booted from via u-boot. Do you know of one which can be deployed and booted directly by the USB downloader? Because if so, I'd be really, really interested in that.

[knc1]

Originally Posted by hjalfi

Actually, I *am* looking for system level customisations; I want to use USB downloader mode to drop a binary into memory and jump to it.
- - - - -

I am pretty sure USB downloader mode only writes to flash.

Boot to u-boot, select bist, then use one of the binary transfer protocols to transfer to ram.
Then you can jump to it.

When you get it completed to your satisfaction, then burn it into flash and set-up u-boot to load and run it.

Duplicating the initialization done by u-boot is a big waste of time.
Plus, you will be limiting the size of your application to the size set aside for u-boot in the flash.
These SoCs boot from a reserved (fixed size) 'hidden' partition of the flash.

Just use the existing bootloader to load your bare metal application (as if it was a kernel, which is also a bare metal application).
This way you will not be limited to the size of the reserved, bootable, partition.

Also, if you don't like u-boot - Freescale also supports red-boot.

[geekmaster]

Originally Posted by knc1

I am pretty sure USB downloader mode only writes to flash. ...

Actually, it can write to RAM too. In fact, that is how it loads and runs the modified uboot images in my "Kindle Select Boot" thread (and which are also used in the kubrick ISO images). I modified those uboot images to boot to main, diags, and fastboot, respectively. And yes, they load from USB downloader mode and they run in kindle RAM. The uboot source cood could be used as a base to launch custom code after it initializes SDRAM and hardware. Beware that uboot inspects the IDME vars to decide how to initialize SDRAM because not all kindles use the same RAM.

Sadly I lost the source code for the uboot mods (and many other projects) when my hard drive AND my backup drive both died within hours of each other (turned out to be bad "spiky" power supply that killed a mobo, two video cards, multiple hard drives, and more).