DMA Crash on MPC8272 - Powerpc

This is a discussion on DMA Crash on MPC8272 - Powerpc ; I am writing a Linux network device driver using Linux 2.4 with an MPC8272 processor. I allocate buffers using kmalloc with the GFP_DMA and GFP_KERNEL flags set. I DMA using these buffers to and from the memory of a PCI ...

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Thread: DMA Crash on MPC8272

  1. DMA Crash on MPC8272

    I am writing a Linux network device driver using Linux 2.4 with an
    MPC8272 processor. I allocate buffers using kmalloc with the GFP_DMA
    and GFP_KERNEL flags set. I DMA using these buffers to and from the
    memory of a PCI device that is not a bus master. When I DMA from the
    buffers to the PCI device, it does not crash, but when I DMA from the
    PCI device to the buffers, the system crashes, sometimes immediately
    and sometimes in as much as a half hour.

    What could cause this difference in behavior based on the direction of
    the DMA?


  2. Re: DMA Crash on MPC8272

    Hiya Bill,

    > [...] When I DMA from the
    > buffers to the PCI device, it does not crash, but when I DMA from the
    > PCI device to the buffers, the system crashes, sometimes immediately
    > and sometimes in as much as a half hour.
    >
    > What could cause this difference in behavior based on the direction of
    > the DMA?


    The last time something like this happened to me, it was because the
    memory destination was wrong and I was overwriting part of the kernel.

    Sounds like pretty similar behaviour.

    Cheers,
    John McCallum
    Edinburgh

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