Re: Boot problems with Fiasco.OC on the NanoPC-T3 Plus

Hey everyone,

thanks for the help, we finally got the board to successfully run the 
hello world application. As suggested we booted the provided Ubuntu 
image and in /proc/interrupts we found that the Timer used is associated 
with the IRQ number 56. Which is strange because the TRM states that the 
same Timer should be the IRQ number 24. We applied the new number and 
got out of the Calibrating timer loop, and after fixing some issues with 
our new timer driver we finally got it to work.

Regarding the RAM, we're still not quite sure why setting the RAM size 
to 2 GB fails, we settled to only specify one GB and call it a day, for 
now.

Thanks again everybody!


Andreas

On 16.01.21 13:33, Andreas Resch wrote:
> Hi Matthias, hi Adam,
>
>
> I can't find anything in the TRM regarding such hardware features in 
> the region where the code exits. It exits right when scanning for the 
> ram size in scan_ram_size at *(unsigned long *)(base_addr + offset) == 
> 0x12345678) with the address as 0x80000000, which is exactly in the 
> middle of the RAM, very strange. Setting the PLATFORM_RAM_SIZE_MB to 
> 1024 and removing the method setup_memory_map from our 
> Platform_arm_s5p6818 class boots as well. I'm starting to think that 
> the culprit is inside the bootloader that is just a 'hacked' version 
> of a 'hacked' version of u-boot 2016.01 I forked at 
> https://github.com/reschandreas/NanoPC-T3Plus/tree/master/U-Boot , 
> could that assumption be correct?
>
> Regarding the timer, my teammate implemented a new driver and it looks 
> like the timer is counting. However, we're now suspecting that our 
> interrupt controller is not correctly initialized although we're doing 
> it exactly like other Platforms with the GIC-400 and we have checked 
> the base addresses several times.
>
> Sadly the only running Linux version we could find is one really old 
> one from friendlyarm where we couldn't extract meaningful information.
>
>
> Andreas
>
> On 15.01.21 01:27, Adam Lackorzynski wrote:
>> On Thu Jan 14, 2021 at 23:54:38 +0100, Matthias Lange wrote:
>>> On [14-01-2021 23:24], Andreas Resch wrote:
>>>> Hello everyone,
>>>>
>>>> as part of a practical course at my university my group has to 
>>>> bring Fiasco.OC and L4re to the NanoPC-T3 Plus which is powered by 
>>>> the S5P6818 from Samsung/Nexell.
>>>> We’re currently stuck on multiple fronts, and as a sort of last 
>>>> resort I’m asking here for help, I hope you don’t mind.
>>>>
>>>> 1. Problem - The RAM
>>>> We implemented a working uart driver for our board and when using 
>>>> all (seemingly) correct values for the RAM region (as stated in the 
>>>> TRM is located from 0x40000000 to 0xc0000000) our SBC only boots up 
>>>> to the message “Hello from Startup::stage2” and then hangs in the 
>>>> function Kmem_alloc::Kmem_alloc() , we believe because the value of 
>>>> Map_base is with 0xffff000040000000 far too big but haven’t found a 
>>>> way to fix this issue whilst keeping the correct RAM region. Does 
>>>> someone have an idea why setting the incorrect RAM region results 
>>>> in more progress in the boot process (as stated in the following 
>>>> paragraph)?
>> 0xffff000040000000 is a virtual address, and is the start of the memory
>> mapping in Fiasco. This looks like the memory is already used in the
>> platform, as Matthias already suspected.
>>
>>> The reason most likely is that the kernel touches a memory region 
>>> that is
>>> reserved or used by someone else (e.g. by ARM Trusted Firmware). The 
>>> TRM
>>> usually only tells you the hardware features. You might get a better 
>>> insight
>>> by looking into the device tree (e.g. from Linux) for your platform. 
>>> Look out
>>> for the "memory" node.
>> But use the one on the target as the bootloader (probably) fills out 
>> those fields.
>>
>>>> 2. The Timer - or the lack thereof
>>>> When we were experimenting with the RAM size we found that when 
>>>> setting to to 3GB starting from 0x40000000 we achieve slightly more 
>>>> output. Right up to ARM generic timer, which seems to not work on 
>>>> this particular board, we decided to implement our own timer 
>>>> driver, now we are stuck at Panic: Trace buffer size unaligned 
>>>> which, upon investigation, was an output from the JDB; by disabling 
>>>> the debugger we could again get more output, seen below. The clock 
>>>> doesn’t seem to start counting and I currently have no idea how to 
>>>> implement my own clock driver, I was hoping the generic clock would 
>>>> suffice.
>>> Here I would also recommend looking into the device tree for 
>>> figuring out the
>>> available timers on the platform. Then you could either sneak into 
>>> the Linux
>>> driver or use the TRM to implement your own driver.
>> TBH, I wouldn't believe the generic timer would not work.
>> General hint, look at the running OS on the box, i.e., Linux, such as
>> dmesg, /proc etc, it tells many things about the platform.
>>
>>
>>
>> Adam


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