Problem running RTEMS on raspberrypi3
Niteesh
gsnb.gn at gmail.com
Mon Dec 16 13:01:15 UTC 2019
I got uboot running on my raspi3. But I can't figure out to load and run a
custom kernel. Can you explain the steps or point me to some
reference.
On Mon, Dec 16, 2019 at 5:13 PM Niteesh <gsnb.gn at gmail.com> wrote:
> On Mon, Dec 16, 2019 at 2:36 AM Christian Mauderer <list at c-mauderer.de>
> wrote:
>
>>
>>
>> On 15/12/2019 21:29, Niteesh wrote:
>> >
>> >
>> > On Mon, Dec 16, 2019 at 12:53 AM Christian Mauderer <list at c-mauderer.de
>> > <mailto:list at c-mauderer.de>> wrote:
>> >
>> > On 15/12/2019 19:46, Niteesh wrote:
>> > >
>> > >
>> > > On Sun, Dec 15, 2019 at 10:15 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:
>> > >
>> > > Hello Niteesh,
>> > >
>> > > On 15/12/2019 09:05, Niteesh wrote:
>> > > > I am trying to get RTEMS examples running on the RPI3, the
>> > RPI3 is
>> > > > similar to RPI2 so the examples built for RPI2 should
>> > technically
>> > > run on
>> > > > the RPi3.But they don't :(, I am really sure of what is
>> causing
>> > > the problem.
>> > >
>> > > Note that there are at least two different versions of the
>> > RPi3 which
>> > > use different chips. The original RPi3 which uses a BCM2837
>> > (same like
>> > > later versions of RPi2) and the RPi3+ which uses a BCM2837B0.
>> > Broadcom
>> > > is always quite sparse with documentation so it's not easy to
>> > tell the
>> > > differences. Which one do you have?
>> > >
>> > > I have Rpi3 model b v1.2 which uses BCM2837 SOC, in my bare-metal
>> > > programming I used the
>> > > 2835 doc as a reference because the only major difference these
>> > two SOC
>> > > is the peripheral base address
>> > > offset. But this is arm cpu is also capable of executing in 64bit
>> > mode.
>> >
>> > OK. Did you check, whether the offset is correct? In the
>> raspberrypi.h
>> > in RTEMS there is the following define:
>> >
>> > #if (BSP_IS_RPI2 == 1)
>> > #define RPI_PERIPHERAL_BASE 0x3F000000
>> > #else
>> > #define RPI_PERIPHERAL_BASE 0x20000000
>> > #endif
>> >
>> > The offsets are right.
>>
>> Good.
>>
>> >
>> > >
>> > > > I followed the steps
>> > > >
>> > >
>> > from
>> http://alanstechnotes.blogspot.com/2013/03/running-your-first-rtems-program-on.html
>> (modified
>> > > > commands to use rtems5) to build the kernel img.
>> > >
>> > > It's a bit odd that the Bootloader doesn't use some image
>> > format like
>> > > U-Boot but if that's the case for Raspberry, that's OK.
>> > >
>> > > Do you want me to try U-Boot, I was planning to use it for my
>> > bare-metal
>> > > stuff because copying the kernel
>> > > to SD-card was a real pain. Will it even work with RTEMS?
>> >
>> > The manual that you linked uses the default Raspberry bootloader.
>> I'm
>> > not sure whether it's an U-Boot. If you skip the bootloader
>> entirely,
>> > your SDRAM might isn't initialized.
>> >
>> > The manual uses the default bootloader. I don't think we have to worry
>> > about the SDRAM initialization
>> > because all of that is taken care of by the GPU.
>>
>> Sounds OK.
>>
>> > When using Uboot, the
>> > GPU will load the uboot image and
>> > pass the control to the CPU. And then the uboot continue's it's
>> execution.
>> >
>>
>> I don't wanted to suggest to use an extra U-Boot. I was just not sure
>> whether the stage 3 loader is an U-Boot. Your approach sounds fine so far.
>>
>> >
>> >
>> > PS: You answered that further below. You are using the stage 3
>> loader.
>> >
>> > >
>> > > > I did try running it on
>> > > > Qemu but it doesn't always work, sometimes it gives
>> > weird output.
>> > >
>> > > How did you run it on Qemu? Did you build some image for that
>> too?
>> > >
>> > > qemu-system-arm -M raspi2 -m 1G -kernel hello.exe -serial
>> mon:stdio
>> > > -nographic
>> > > *
>> > > *
>> > > *
>> > > qemu-system-aarch64: GLib: g_mapped_file_unref: assertion 'file !=
>> > NULL'
>> > > failed *I get this error
>> > > while trying to emulate raspi3.
>> >
>> > That sounds like a problem with Qemu. Is there some official test
>> image
>> > for rpi3 on qemu? Note that this isn't really relevant for your
>> current
>> > problem. So if you don't have some manual just ignore the question.
>> >
>> > >
>> > > I ran qemu along with GDB to find what was causing the wrong
>> output. I
>> > > am really not sure if this is right,
>> > > I still have a lot to learn, but my assumption's using GDB are as
>> > follows.
>> > > There are 4 active thread which run the same code.
>> > >
>> > > (gdb) info thread
>> > > Id Target Id Frame
>> > > * 1 Thread 1.1 (CPU#0 [running]) _start () at
>> > >
>> >
>> ../../../../../../../../rtems/c/src/lib/libbsp/arm/raspberrypi/../../../../../../bsps/arm/shared/start/start.S:153
>> > > 2 Thread 1.2 (CPU#1 [running]) _start () at
>> > >
>> >
>> ../../../../../../../../rtems/c/src/lib/libbsp/arm/raspberrypi/../../../../../../bsps/arm/shared/start/start.S:153
>> > > 3 Thread 1.3 (CPU#2 [running]) _start () at
>> > >
>> >
>> ../../../../../../../../rtems/c/src/lib/libbsp/arm/raspberrypi/../../../../../../bsps/arm/shared/start/start.S:153
>> > > 4 Thread 1.4 (CPU#3 [running]) _start () at
>> > >
>> >
>> ../../../../../../../../rtems/c/src/lib/libbsp/arm/raspberrypi/../../../../../../bsps/arm/shared/start/start.S:153
>> >
>> > In this case that are not threads but it's the CPU cores. GDB shows
>> them
>> > as threads. Most likely it wouldn't be able to detect the RTEMS
>> threads.
>> >
>> > It's a bit odd that they are all pointing to start.S:153. That's the
>> > entry point for the program. It looks like not even one instruction
>> has
>> > been executed yet.
>> >
>> > I took this output before executing the program, that the reason why not
>> > even a single instruction has been
>> > executed yet.
>>
>> OK.
>>
>> >
>> > >
>> > > After some time one of the thread call's the BSP reset function
>> > this is
>> > > when the program crashes, the other threads complain "*executing
>> > thread
>> > > is NULL*"
>> >
>> > I would rather assume that one core tries to do the initialization
>> while
>> > the others hang in a endless loop till they are needed. The one core
>> > doing the initialization work hits an exception somewhere and calls
>> the
>> > exception handler which calls the bsp reset function.
>> >
>> > The executing thread is NULL is a sign that it happens somewhere
>> during
>> > initialization when the RTEMS threading hasn't been started yet.
>> >
>> > The PC has an odd value. The linker command file tells that there
>> is a
>> > RAM_MMU at 0x00100000. It only puts a bsp_translation_table there
>> but
>> > there shouldn't be any code. So I don't know what the processor is
>> doing
>> > there. You could try to set a breakpoint on the address 0x00100fc4
>> and
>> > take a look at why the processor is there with a "bt" (backtrace).
>> >
>> > When I re-run it again, it now stops at a different address. As you said
>> > that the other cores are put
>> > in an endless loop, I don't think that's is happening. I single stepped
>> > the instruction and later at some point checked the threads
>> >
>> > (gdb) info threads
>> >
>> >
>> > Target Id Frame
>> > 1 Thread 1.1 (CPU#0 [running]) arm_ccsidr_get_line_power
>> > (ccsidr=<optimized out>)
>> > at
>> >
>> /home/niteesh/development/rtems/kernel/rtems/cpukit/score/cpu/arm/include/libcpu/arm-cp15.h:850
>> > 2 Thread 1.2 (CPU#1 [running]) arm_cp15_cache_invalidate_level
>> > (inst_data_fl=0, level=1)
>> > at
>> >
>> /home/niteesh/development/rtems/kernel/rtems/cpukit/score/cpu/arm/include/libcpu/arm-cp15.h:1162
>> > 3 Thread 1.3 (CPU#2 [running]) arm_ccsidr_get_line_power
>> > (ccsidr=<optimized out>)
>> > at
>> >
>> /home/niteesh/development/rtems/kernel/rtems/cpukit/score/cpu/arm/include/libcpu/arm-cp15.h:850
>> > * 4 Thread 1.4 (CPU#3 [running])
>> > arm_cp15_get_cache_size_id_for_level (level_and_inst_dat=0)
>> > at
>> >
>> /home/niteesh/development/rtems/kernel/rtems/cpukit/score/cpu/arm/include/libcpu/arm-cp15.h:936
>> > (gdb)
>> >
>> > They all are executing different instructions at the same time.
>>
>> Some of the initialization is done on all cores. Some isn't. I took a
>> look at the initialization and it seems that I was wrong: There is no
>> wait loop. All processors are running through the initialization
>> process. Some just skip parts. The part where they really start to
>> differ is in bsp_start_hook_0.
>>
>> > I> googled about just running one thread or CPU as you said at a time
>> and
>> > used "*set scheduler-locking on" *on doing this I always get the right
>> > output.
>> >
>> > (gdb) info threads
>> > Id Target Id Frame
>> > * 1 Thread 1.1 (CPU#0 [running]) bsp_reset ()
>> > at
>> >
>> ../../../../../../../../rtems/c/src/lib/libbsp/arm/raspberrypi/../../../../../../bsps/arm/raspberrypi/start/bspreset.c:18
>> > 2 Thread 1.2 (CPU#1 [running]) _start ()
>> > at
>> >
>> ../../../../../../../../rtems/c/src/lib/libbsp/arm/raspberrypi/../../../../../../bsps/arm/shared/start/start.S:153
>> > 3 Thread 1.3 (CPU#2 [running]) _start ()
>> > at
>> >
>> ../../../../../../../../rtems/c/src/lib/libbsp/arm/raspberrypi/../../../../../../bsps/arm/shared/start/start.S:153
>> > 4 Thread 1.4 (CPU#3 [running]) _start ()
>> > at
>> >
>> ../../../../../../../../rtems/c/src/lib/libbsp/arm/raspberrypi/../../../../../../bsps/arm/shared/start/start.S:153
>> > (gdb)
>> >
>> > The above command allow's only a single thread to run.
>>
>> Maybe there is a timing difference between the simulator and the real
>> hardware. I'm not sure how well tested the SMP code is on the Raspberry.
>> There can be a hidden bug.
>>
>> Just a guess: If there is a bug it could be possible that you hit it
>> with your rpi3 too. Maybe it would be good to try a single core version
>> of the BSP. I assume you have configured with "--enable-smp"? Can you
>> try to build without it?
>>
> I built 2 versions with SMP enabled and disabled, the one we are talking
> about is the SMP disabled version, I ran
> the example with SMP enabled, still, the error's are similar, I only
> difference is, in the disabled one, there are only 4 or less panic's
> (maybe corresponding to 4 cpu's) but the other one has a higher number of
> panics.
>
> > Won't it be a good idea to make a separate BSP for rpi3?
>>
>> As soon as it is necessary: Sure. But from what you told me it seems
>> that the hardware is very similar so that we won't hit this point soon.
>> Or do you already see differences that would make it necessary.
>>
>> I haven't had a look at the details but it could also be possible to
>> unify the BSPs and entirely remove the rpi2 variant if the information
>> from the flattened device tree are used.
>>
> Can you explain how FDT work in RTEMS. Can you mention some BSP's which
> use FDT so I can use them as a reference to learn.
> I previously took a look at the beagle FDT project (#3784), you mentioned
> about hardcoded values and initialization functions, can
> you explain more about what exactly do the initialization functions do? Do
> they assign a function to a particular pin, like in raspi
> the pins are multiplexed for various functions, so do the initialization
> functions assign those pins to a particular function?
>
> And also please explain how does the initialization of the system happen
> from the DT file.
>
>> >
>> > > *** FATAL ***
>> > > fatal source: 9 (RTEMS_FATAL_SOURCE_EXCEPTION)
>> > >
>> > > R0 = 0x400005e6 R8 = 0x00000000
>> > > R1 = 0x00000001 R9 = 0x00000000
>> > > R2 = 0xbffffa1a R10 = 0x00000000
>> > > R3 = 0x00000000 R11 = 0x00000000
>> > > R4 = 0x002001db R12 = 0x00000000
>> > > R5 = 0x00000000 SP = 0x00300bd0
>> > > R6 = 0x00000000 LR = 0x00100fc4
>> > > R7 = 0x00000000 PC = 0x00100fc4
>> > > CPSR = 0x000001d3 VEC = 0x00000002
>> > > FPEXC = 0x40000000
>> > > FPSCR = 0x00000000
>> > > D00 = 0x0000000000000000
>> > > D01 = 0x0000000000000000
>> > > D02 = 0x0000000000000000
>> > > D03 = 0x0000000000000000
>> > > D04 = 0x0000000000000000
>> > > D05 = 0x0000000000000000
>> > > D06 = 0x0000000000000000
>> > > D07 = 0x0000000000000000
>> > > D08 = 0x0000000000000000
>> > > D09 = 0x0000000000000000
>> > > D10 = 0x0000000000000000
>> > > D11 = 0x0000000000000000
>> > > D12 = 0x0000000000000000
>> > > D13 = 0x0000000000000000
>> > > D14 = 0x0000000000000000
>> > > D15 = 0x0000000000000000
>> > > D16 = 0x0000000000000000
>> > > D17 = 0x0000000000000010
>> > > D18 = 0x0000000000000000
>> > > D19 = 0x0000000000000000
>> > > D20 = 0x0000000000000000
>> > > D21 = 0x0000000000000000
>> > > D22 = 0x0000000000000000
>> > > D23 = 0x0000000000000000
>> > > D24 = 0x0000000000000000
>> > > D25 = 0x0000000000000000
>> > > D26 = 0x0000000000000000
>> > > D27 = 0x0000000000000000
>> > > D28 = 0x0000000000000000
>> > > D29 = 0x0000000000000000
>> > > D30 = 0x0000000000000000
>> > > D31 = 0x0000000000000000
>> > > RTEMS version:
>> > 5.0.0.c6d8589bb00a9d2a5a094c68c90290df1dc44807-modified
>> > > RTEMS tools: 7.5.0 20191114 (RTEMS 5, RSB
>> > > 83fa79314dd87c0a8c78fd642b2cea3138be8dd6, Newlib 3e24fbf6f)
>> > > executing thread is NULL
>> > >
>> > > > The steps that I followed are:
>> > > > 1. Created a bootable SD card using raspbian.
>> > > > 2. Replaced the kernel.img file with RTEMS kernel.img file
>> and
>> > > modified
>> > > > the config.txt to boot from the RTEMs kernel (boots in
>> > aarch32 bit
>> > > mode).
>> > > > I am still not able to wrap my head around the RPI bsp build
>> > process.
>> > > > This is what I understood as of now, correct me if I am
>> wrong.
>> > > > Both RPi and Rpi2 are based on the same BSP, they just
>> > differ in the
>> > > > peripheral offsets, hardcoded checks are used to select the
>> > right
>> > > offset
>> > > > at the time of compiling
>> > >
>> > > >From what I know of the Raspberry BSPs that is correct.
>> > >
>> > > > and the linkercmd file is responsible for
>> > > > building the final executable file.
>> > >
>> > > The linkercmd file is - like for all programs - responsible
>> > where the
>> > > memory regions are that can be used for code or data. So you
>> > could more
>> > > or less explain it like you did.
>> > >
>> > > > I looked at the linker script, it seem's to have the start
>> > section at
>> > > > address 0x200000, I also loaded it in GDB and the start
>> > address is
>> > > > *Start address 0x200080,*
>> > >
>> > > I agree with that. The different start in GDB is most likely
>> > because
>> > > there is a vector table in front (at least if the Broadcom
>> chip is
>> > > similar to a lot of other processors that I have encountered).
>> > >
>> > > Does that mean that you have a debugger connected to the
>> > raspberry? Can
>> > > you load code with it? If yes: Is the bootloader executed
>> > before you
>> > > load your code? Otherwise the SDRAM might isn't initialized
>> yet.
>> > >
>> > > I don't have a debugger connected to it. I from what I have SDRAM
>> is
>> > > initialized by the 3 stage bootloader(start.elf).
>> >
>> > That should be OK and it answers my question above.
>> >
>> > >
>> > > > I did some bare metal programming on RPI3
>> > > > there I had the start section at address 0x8000 Is this
>> causing
>> > > the problem?
>> > >
>> > > I assume that you used some internal RAM when you did bare
>> metal
>> > > programming. You maybe even skipped one or two bootloader
>> > stages. From a
>> > > quick look Raspberry has a quite complex boot process with at
>> > least
>> > > three bootloaders:
>> > http://lions-wing.net/maker/raspberry-1/boot.html
>> > >
>> > > I don't think I have skipped any stages. The boot process is
>> > exactly the
>> > > same as how it boot's a normal raspbian or any other linux
>> > > distro, I just to replace the linux kernel with my own kernel.
>> >
>> > Sounds reasonable. Does the bootloader print anything where it puts
>> the
>> > kernel image? Maybe the start address changed during the raspberry
>> > versions.
>> >
>> > the default kernel load address is 0x8000 in 32bit mode and 0x80000 in
>> > 64bit mode I have no idea about the raspberry 1,
>> > but the load address is same for rpi2 and 3.
>>
>> That sounds odd. Do you have a memory map somewhere? From the linker
>> command file it seems quite clear that RTEMS is build for a 0x200000.
>>
>> >
>> > >
>> > >
>> > > > I have no idea on how to debug this, any suggestion on how
>> > to start
>> > > > would be really helpfull.
>> > > >
>> > >
>> >
>>
>
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