raspberry BSP: Maybe there is a bug in the linker file?
Niteesh
gsnb.gn at gmail.com
Sat Dec 21 09:36:32 UTC 2019
Looks like there is already framebuffer support for RPi, but still I would
like to play with it and add some GUI example as in
https://blog.thelunatic.dev/gsoc-final-report/
On Sat, Dec 21, 2019 at 2:32 PM Niteesh <gsnb.gn at gmail.com> wrote:
> I am very much interested in taking part in GSOC 2020. I want to get this
> running on raspberrypi3
> so that I could start learning and exploring more of RTEMS. I am planning
> to add framebuffer support, using this year's GSOC work
> on beagle bone as a reference.
> On Sat, Dec 21, 2019 at 2:20 PM Christian Mauderer <list at c-mauderer.de>
> wrote:
>
>> On 21/12/2019 08:28, Niteesh wrote:
>> > Did you take a look at the exception?
>>
>> Not yet.
>>
>> > I still couldn't get it running on
>> > the rpi3 using rpi2 bsp.
>>
>> Again: It's quite likely that the serial interface is a problem. I don't
>> think that you'll see any output on rpi3 without changes.
>>
>> > I built the bsp again by checking out a commit before
>> > c5fd79cd4704a4270ba0114a1009ab8556f997c9
>> > and created a kernel.img using objcopy.
>>
>> That should work. But Most likely you'll get your output on the serial
>> interface that is pointing to the bluetooth module.
>>
> I configured such that PL011 it is pointing to the serial port. We can do
> that by adding disable-bt in the config.txt file.
>
>> > I tried running it on gdb with set scheduler-locking on. I seem to jump
>> > to bsp_vector_table_begin and hang there (0x000000c).
>>
>> I thought you don't have a debugger connected? How do you run it with gdb?
>
> Ran the executable with qemu and connected to it.
> qemu-system-arm -M raspi2 -m 1G -kernel hello.exe -serial mon:stdio
> -nographic -S -s
>
>>
>> >
>> >
>> > On Sat, Dec 21, 2019 at 1:42 AM Christian Mauderer <list at c-mauderer.de
>> > <mailto:list at c-mauderer.de>> wrote:
>> >
>> > On 20/12/2019 19:19, Niteesh wrote:
>> > > How do you test a patch? Do you checkout that particular commit
>> and
>> > > build and the BSP again?.
>> >
>> > Basically yes: You check out the version that you want fixed and
>> apply
>> > the patch. In that case I have gone back and forward a few times to
>> find
>> > the commit that introduced the second bug.
>> >
>> > > @Christian Mauderer <mailto:list at c-mauderer.de
>> > <mailto:list at c-mauderer.de>> how did you build it
>> > > for the rpi1? Did you follow the steps as in previous threads?
>> >
>> > Basically the same steps like for every BSP:
>> > 1. Build a recent toolchain using RSB.
>> > 2. Build the BSP.
>> > 3. Test it on the board.
>> >
>> > For the rpi1 the BSP is "raspberrypi" instead of "raspberrypi2".
>> And I
>> > didn't install the BSP because I only wanted the tests and no extra
>> > application.
>> >
>> > For testing it I used the guide that you found: Objcopy into a
>> binary
>> > file and replace the kernel.img with it.
>> >
>> > > and how did you come to the conclusion that these changes cause
>> the
>> > > exceptions,
>> >
>> > I had a look at the history of the raspberry BSP (`gitk
>> > bsps/arm/raspberrypi` or `git log bsps/arm/raspberrypi`) and looked
>> for
>> > suspicious patches. For the raspberry there are not much patches in
>> the
>> > last year so that was quite easy. Then I just tested before and
>> after
>> > some of the patches to find the ones that introduced the bugs.
>> >
>> > Again: In this case it was necessary to backport Sebastians patch so
>> > that I have been able to test before / after the one that
>> introduces the
>> > exception.
>> >
>> > I haven't had a detailled look at the exception yet but I assume
>> it's
>> > some problem that the wrong variant is used or that my RPi1 is an
>> early
>> > model with less RAM or something like that.
>> >
>> > > as a beginner these ideas
>> > > will help in the future.
>> > > On Fri, Dec 20, 2019 at 2:46 PM Christian Mauderer
>> > <list at c-mauderer.de <mailto:list at c-mauderer.de>
>> > > <mailto:list at c-mauderer.de <mailto:list at c-mauderer.de>>> wrote:
>> > >
>> > > On 20/12/2019 09:22, Christian Mauderer wrote:
>> > > > On 20/12/2019 07:33, Sebastian Huber wrote:
>> > > >> On 19/12/2019 15:28, Niteesh wrote:
>> > > >>> As far as I know, 0x8000 is a fixed address where the
>> > bootloader
>> > > jumps
>> > > >>> to after loading the application assuming the CPU is in
>> > 32bit mode.
>> > > >>> For 64bit mode, it jumps to 0x80000.
>> > > >>
>> > > >> Would you mind testing this patch:
>> > > >>
>> > > >>
>> > https://lists.rtems.org/pipermail/devel/2019-December/056551.html
>> > > >>
>> > > >
>> > > > On the Pi 1 now the binary has three time the size (with a
>> > lot of 0x00
>> > > > in it) and at least RTEMS starts. But it runs into an
>> > exception quite
>> > > > fast. I'll investigate that a bit.
>> > > >
>> > > > @Niteesh: For the Pi 3 I would expect that it still doesn't
>> > print
>> > > > anything on the console due to the different UART pins.
>> > > >
>> > > > The output on the Pi 1 is:
>> > > >
>> > > > executing�
>> > > > *** FATAL ***
>> > > > fatal source: 9 (RTEMS_FATAL_SOURCE_EXCEPTION)
>> > > >
>> > > > R0 = 0xfc037f80 R8 = 0x00000000
>> > > > R1 = 0xfc345980 R9 = 0x00000010
>> > > > R2 = 0x00000001 R10 = 0xfc037f8a
>> > > > R3 = 0x03fc8080 R11 = 0x0030da00
>> > > > R4 = 0xfc037f80 R12 = 0xfc345988
>> > > > R5 = 0x00000008 SP = 0x00300ba8
>> > > > R6 = 0x0030d9fe LR = 0x00205a78
>> > > > R7 = 0x00305218 PC = 0x00205ac8
>> > > > CPSR = 0x600001d3 VEC = 0x00000004
>> > > > RTEMS version:
>> 5.0.0.254f38583fe68c3e17dfe274a2deeb00a5a538d6
>> > > > RTEMS tools: 7.5.0 20191114 (RTEMS 5, RSB 5 (6c65fc237b9e
>> > modified),
>> > > > Newlib d14714c69)
>> > >
>> > > The exception seems to be caused by some of the changes in
>> > bspstart.c
>> > > and bspgetworkarea.c in patch
>> > a4d7e4cee77d16b0e34ef543f0804e7eb2954137.
>> > > So the fix for the linker command file is fine.
>> > >
>> >
>>
>
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