rtems-boot-image tool: Raspberry Pi

Sun Apr 5 06:34:55 UTC 2020

Hii,
It has been quite a few days since the last mail.
Chris, can you please take a look at this when you are free?

Thanks,
Niteesh

On Mon, Mar 23, 2020 at 1:23 AM Christian Mauderer <list at c-mauderer.de>
wrote:

> Hello Niteesh,
>
> thanks for the (private) remainder. This thread really stopped quite
> some time ago. A lot of us are quite busy right now but that shouldn't
> happen. If you don't get a response for some question: Please give it
> about a week of time and then just ping the thread.
>
> On 05/03/2020 11:06, G. S. Niteesh wrote:
> > On Wed, Feb 26, 2020 at 8:39 AM Chris Johns <chrisj at rtems.org
> > <mailto:chrisj at rtems.org>> wrote:
> >
> >     On 22/2/20 1:45 am, G. S. Niteesh wrote:
> >     > Hi,
> >     >
> >     > This is regarding adding RPi support to the boot image generation
> >     tool.
> >     >
> >     > The boot process for Raspberry Pi is very unconventional. The GPU
> >     starts
> >     > first, initializes RAM, other hardware, loads the bootloaders and
> >     then starts
> >     > the ARM CPU.
> >     >
> >     > The minimum files that are required to boot an RPi are
> >     > bootcode.bin, startx.elf, fixup.dat, kernel.img, config.txt
> >     > There are also other variants of startx.elf and fixup.dat.
> >     > Please have a look
> >     >
> >     at
> https://www.raspberrypi.org/documentation/configuration/config-txt/boot.md
> >     > for information on the variants.
> >     >
> >     > From what I have tried on my Rpi3 model b v1.2 the minimum files
> >     that are
> >     > required are start_x.elf, fixup_x.dat, bootcode.bin, kernel.img,
> >     config.txt
> >     > But for this to work, we must add start_x=1 to config.txt because
> >     by default
> >     > start.elf is loaded.
> >
> > Hello Chris,
> >
> >
> >     I would have look at how the tool maps to RPi to know if it needs
> >     more work :)
> >
> >
> > Did you take a look at it?
>
> Chris is most likely too busy with the release right now.
>
> >
> > In my opinion, there are two ways to do it.
> > The first would be to modify the U-Boot bootloader object to have a
> > files field
> > to make sure the user provides all the necessary files(fixup.dat,
> > startx.elf, config.txt).
> > So after this change the rtems-boot.ini for RPI should look something
> > like this
> > [u-boot-raspberrypi]
> > uses = u-boot-arm-raspberrypi
> > ..
> > ..
> > first_stage = %{ubootdir}/bootcode.bin
> > boot_device = mmc 0
> > second_stage = uboot or startx
> > files = [config.txt, fixup.dat etc]
> > But also please keep in mind that if we want to support RPi4 then the
> > first_stage
> > will start4x.elf since bootcode.bin is now replaced by code in the
> > EEPROM in RPi4 SOC.
>
> As far as I understand that approach it more or less tells: To start a
> raspberry you need U-Boot. U-Boot needs the fixup.dat, startx.elf and
> config.txt to boot. But that sounds a bit wrong. On Raspberry U-Boot is
> purely optional, isn't it? So from a high-level view it would be more a
>
> - Raspberry needs fixup.dat, startx.elf and config.txt
> - That can start either:
>   - an application or
>   - an U-Boot which can then start an application (or do other things)
>
> >
> > Another approach will be to create the default Raspberry Pi bootloader
> > object. But having
> > support for U-Boot is important since it will allow for automatic
> testing.
>
> That approach sounds more correct. But I don't really know the
> rtems-boot-image tool. That makes it a lot harder for me to tell whether
> that approach works well. From that ignorant position I would say that
> it would be nice to have a boot-image command that can be called with or
> without a option (like --with-u-boot). Alternatively maybe two targets
> would be possible. One raspiboot-u-boot-pi1 and one raspiboot-raw-pi1.
>
> But your best bet might is to wait for Chris to get free again and
> answer that question. He knows the boot image tool and can tell you a
> lot better which concept works best.
>
> Best regards
>
> Christian
>
> >
> > Which one do you think is a better approach?
> >
> > Thank you.
> >
> >
> >     >
> >     > So, what should be the values for the first and second stages in
> >     rtems-boot.ini
> >     > for Rpi?
> >
> >     Would this be bootcode.bin?
> >
> >     > And also wouldn't it be nice if we could add a files field, which
> >     will copy the
> >     > specified files to the image? This would save a lot of typing in
> >     case of RPi
> >
> >     Do you have an example?
> >
> >     Chris
> >
> >
> > _______________________________________________
> > devel mailing list
> > devel at rtems.org
> > http://lists.rtems.org/mailman/listinfo/devel
> >
>
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