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Altera_Forum's avatar
Altera_Forum
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13 years ago

Device tree corrupted

Hi all,

I use a 3.2.0 kernel from Altera git on a nios2, I have no bootloader and an initramfs. the kernel is loaded directly from Flash using altera_nios2/boot_loader_cfi.srec

The kernel succeed to boot however I have corrupted values in /proc/device-tree. For instance in /proc/device-tree/sopc@0/gpio@0x2000120compatible : 


hexdump -C /proc/device-tree/sopc@0/gpio@0x2000120/compatible 
00000000  68 69 73 20 68 65 6c 70  20 6d 65 73 73 61 67 65  |his help message|
00000010  20 61 6e 64 20 65 78 69  74 00 00                 | and exit..|

It is the same for each of my devices in the device-tree. I search for those corrupted values and found that they comes from rootfs.initramfs file generated by uClinux

I really don't know how to fix this. It is a big problem since I can't even drive a GPIO :(.

I found some old forums that talk about a similar issue :

http://comments.gmane.org/gmane.linux.uclinux.nios2.devel/692

There is no solution and this forum seems dead.

Does someone had the same issue ?

And does one find a solution ?

Best regards

1 Reply

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    13 years ago

    Hi,

    So after (a long) investigation I think I can explain what happens, but I don't know how to correct since it may come from the kernel sources (I'm not kernel developper).

    If I dump device-tree values before starting any application the device-tree (DT) is not corrupted.

    If I start an application that requires quite a lot of memory (such as net-snmp with V3 and encryption/authentication enabled) the device tree becomes corrupted.

    It seems that applications that requires quite a lot of memory are overwritting DT values.

    So I configure my GPIOs before DT corruption and everything works fine.

    But this is not really a solution.

    So I think that the DT area is not protected from a kernel point of vu, so the memory used by the DT is overwritten when kernel needs more memory.

    I don't know if the issue comes from the kernel itself or from uClinux stuffs.

    Does someone has any idea ?

    Best regards

    PS : the more strange behaviour is that with a 16MB RAM the DT needs more applications running to be corrupted, with a 32MB RAM the DT is corrupted after the first application launched?