ARM Integrator-CP Bare Bones

[tharkun]

Hi everybody, for all those interested I've put together a working ARM Bare Bones tutorial for the wiki. Here it is.
All it does currently is boot and display "hello, world" via the serial port, I'm planning on updating it soon to use the LCD screen and possibly the PIC, Mouse, Keyboard and Interrupts.
Please note that it is still a work in progress.

[Combuster]

Well, right now it looks like a working hack, but that doesn't mean it can't be fixed:
- you use qemu's -kernel option. That means qemu does the ELF loading for you and puts the various parts of the binary in the locations they belong. However, on a real ARM execution doesn't automagically begin at _start, but at some fixed address. What/how's the task of the bios performed on real hardware? How do you run your kernel on a real integrator board?

- You fix the stack at 64k growing downward. Please comment on that as it will probably end up in your data section once the kernel grows to some size.

Keep up the good work!

[pcmattman]

You may also want to clarify that the tutorial is for the Integrator/CP boards that QEMU emulates, rather than promoting it as a complete generic ARM barebones.

[tharkun]

- you use qemu's -kernel option. That means qemu does the ELF loading for you and puts the various parts of the binary in the locations they belong. However, on a real ARM execution doesn't automagically begin at _start, but at some fixed address. What/how's the task of the bios performed on real hardware? How do you run your kernel on a real integrator board?

I'm currently working on that, I'm reading through the Integrator-CP docs as write this. AFAICT the top 256KiB of the flash memory is reserved for system boot code. This boot code is mapped to address 0x20000000, and the rest of the flash memory is mapped to 0x24000000.

EDIT: The boot code actually starts at an address depending on the size of the flash memory, e.g if your flash memory is 16MiB, then your boot code will start at 0x24FC0000. (0x24000000 + (16MiB - 256KiB))

- You fix the stack at 64k growing downward. Please comment on that as it will probably end up in your data section once the kernel grows to some size.

Fixed, I've changed the kernel starting address to 0x10000, just above the stack, which has been change to start at 0xFFFC, growing downward. This is subject to further change, as I'm planning on writing the boot code and moving the kernel to 0x24000000.

You may also want to clarify that the tutorial is for the Integrator/CP boards that QEMU emulates, rather than promoting it as a complete generic ARM barebones.

The title of the thread and article have been, changed to ARM Integrator-CP Bare Bones.

[Nathan]

Hi everybody, for all those interested I've put together a working ARM Bare Bones tutorial for the wiki. Here it is.
All it does currently is boot and display "hello, world" via the serial port, I'm planning on updating it soon to use the LCD screen and possibly the PIC, Mouse, Keyboard and Interrupts.
Please note that it is still a work in progress.

I will love to see it, because I'm very interested on OS development for mobile platforms, as ARM and MIPS.

Congratulations for the beginning!

[tharkun]

I will love to see it, because I'm very interested on OS development for mobile platforms, as ARM and MIPS.

The bare bones, in it's current state, won't work on real hardware. It's to do with the way QEMU loads the kernel - there's no way to emulate the way real hardware loads it using QEMU (I'm working on this, but AFAICT patching QEMU is the only option)
This however shouldn't be much of a problem as not many people have Integrator/CP boards, as they happen to cost $9500+, the reason I'm writing a tutorial for them is because the documentation for them was fairly easy to find. I originally intended to write a tutorial for the Versatile/PB board that QEMU also emulates, but the I was unable to find any documentation. (Though I would appreciate it if somebody who knows where to find documentation, would tell me )
I'm planning on turning the current bare bones, into more of a step by step tutorial, as this might make it easier to follow - and in my opinion easier to write

Congratulations for the beginning!

Thanks.

[Nathan]

You're Welcome!

Also, I love this, because in the internet I can't find ANY site that had the documentation to help me on this, also I already know about the Qemu problem, because I've already developed some programs for MIPSLinux, then I was using Qemu to emulate, and people said that the Linux won't work on the real hardware. But remember that even if it won't work on the real one, just do it to work on a emulator already help the people too much to get the base needed to continue.

As I'm just beginning, I will love if you put some references on the wiki, where we can get reference to continue developing for this awesome micro-controler!

When I've talked about the references, I was talking about things as how did you know that 0x16000000 was the base for output, and why it should be added to 0x18 to know that the buffer is empty. Things like this that make my head explode on questions that I can't solve by myself.

[tharkun]

When I've talked about the references, I was talking about things as how did you know that 0x16000000 was the base for output, and why it should be added to 0x18 to know that the buffer is empty. Things like this that make my head explode on questions that I can't solve by myself.

I'll add some links and references later, when I get some time. Thanks for the feedback.

[Nathan]

I'm going to wait anxious for the update!

[tharkun]

I've updated it with a 'links' section at bottom of the page. I'll try tomorrow to add a section on interrupt handling (syscalls mainly - I'm still working on the IRQs)

[Nathan]

Thanks very much mate, you're doing a very wonderful and helpful work!

[Nathan]

Also, I'm having some problems to understand both codes, then could you please do a better explanation of the codes?

[Combuster]

Also, I'm having some problems to understand both codes, then could you please do a better explanation of the codes?

Unfortunately for you, no explanation is good enough to actually make you understand. Did you notice the references to the required knowledge?

[Solar]

As hard a wording as you could expect from Combuster, but he's right.

I've never, ever seen ARM assembler before, but I could make perfect sense out of what I saw on first reading.

[montrom]

Cool, I like that you made it a complete tutorial. If I ever get into this kind of thing, I know where to look. Thanks.

http://www.designarm.com/quickstart-gui ... arted.html -- Looks useful too.