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    SubjectRe: Problems with alpha/pci + radeon/ttm
    On 22/06/10 20:32, Dave Airlie wrote:
    > On Tue, Jun 22, 2010 at 3:59 PM, FUJITA Tomonori
    > <> wrote:
    >> On Mon, 21 Jun 2010 17:19:43 -0400
    >> Matt Turner<> wrote:
    >>> Michael Cree and I have been debugging FDO bug 26403 [1]. I tried
    >>> booting with `radeon.test=1` and found this, which I think is related:

    Note that my radeon card is PCI whereas I think Matt may be using an AGP

    My logs are very similar to Matt's except I don't see the following line:

    >>>> pci_map_single failed: could not allocate dma page tables

    >> This happens in the latest git, right?

    Indeed, testing 2.6.35-rc3 (plus a couple or so extra patches to fix
    unrelated compile errors).

    >> Is this a regression (what kernel version worked)?
    >> Seems that the IOMMU can't find 128 pages. It's likely due to:
    >> - out of the IOMMU space (possibly someone doesn't free the IOMMU
    >> space).
    >> or
    >> - the mapping parameters (such as align) aren't appropriate so the
    >> IOMMU can't find space.
    > I don't think KMS drivers have ever worked on alpha so its not a
    > regression, they are working fine on x86 + powerpc and sparc has been
    > run at least once.

    KMS on the console boot up has worked since about 2.6.32, but starting
    up the X server has always failed and, in my case, the system becomes
    unstable and eventually OOPs.

    > I suspect we are simply hitting the limits of the iommu, how big an
    > address space does it handle? since generally graphics drivers try to
    > bind a lot of things to the GART.

    No idea on the address space limit. I applied the patch of Fujita that
    logs all IOMMU allocations, and also inserted some extra printks in the
    ttm kernel code so that I could see which routines failed and the error
    code returned. Running the radeon test on boot exhibits the following:

    [ 238.712768] [drm] Tested GTT->VRAM and VRAM->GTT copy for GTT offset
    [ 239.281127] [drm] Tested GTT->VRAM and VRAM->GTT copy for GTT offset
    [ 239.281127] ttm_tt_bind belched -12
    [ 239.282104] ttm_bo_handle_move_mem belched -12
    [ 239.282104] ttm_bo_move_buffer belched -12
    [ 239.282104] ttm_bo_validate belched -12
    [ 239.282104] radeon 0000:01:00.0: object_init failed for (1048576,
    0x00000002) err=-12
    [ 239.282104] [drm:radeon_test_moves] *ERROR* Failed to create GTT
    object 419
    [ 239.399291] Error while testing BO move.

    Note that no IOMMU allocations are printed while radeon_test_moves is
    running so iommu_arena_alloc doesn't appear to be called. Also the
    error code returned up to radeon_test_moves is -12 which is ENOMEM. So
    does appear to be some memory limit.

    > It might be worth limiting the PCIGART in radeon to 32MB to see if the
    > lower limit helps.

    So, how does one do that?


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