On Tue, Jun 22, 2010 at 3:59 PM, FUJITA Tomonori
<fujita.tomonori@xxxxxxxxxxxxx> wrote:
> On Mon, 21 Jun 2010 17:19:43 -0400
> Matt Turner <mattst88@xxxxxxxxx> 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:
>>
>> > [drm] Tested GTT->VRAM and VRAM->GTT copy for GTT offset 0x202000
>> > [drm] Tested GTT->VRAM and VRAM->GTT copy for GTT offset 0x302000
>> [snip]
>> > [drm] Tested GTT->VRAM and VRAM->GTT copy for GTT offset 0xfd02000
>> > [drm] Tested GTT->VRAM and VRAM->GTT copy for GTT offset 0xfe02000
>> > pci_map_single failed: could not allocate dma page tables
>> > [drm:radeon_ttm_backend_bind] *ERROR* failed to bind 128 pages at 0x0FF02000
>> > [TTM] Couldn't bind backend.
>> > radeon 0000:00:07.0: object_init failed for (1048576, 0x00000002)
>> > [drm:radeon_test_moves] *ERROR* Failed to create GTT object 253
>> > Error while testing BO move.
>>
>> From what I can see, the call chain is
>> radeon_test_moves
>> (radeon_ttm_backend_bind called through callback function)
>> - radeon_ttm.c:radeon_ttm_backend_bind calls radeon_gart_bind
>> - radeon_gart.c:radeon_gart_bind calls pci_map_page
>> - pci_map_page is alpha_pci_map_page, which calls...
>> - alpha_pci_map_page calls pci_iommu.c:pci_map_single_1
>> - pci_map_single_1 calls iommu_arena_alloc
>> - iommu_arena_alloc calls iommu_arena_find_pages
>> - iommu_arena_find_pages returns non-0
>> - iommu_arena_alloc returns non-0
>> - pci_map_single_1 returns 0 after printing
>> "could not allocate dma page tables" error
>> - alpha_pci_map_page returns 0 from pci_map_single_1
>> - radeon_gart_bind returns non-0, error path prints
>> "*ERROR* failed to bind 128 pages at 0x0FF02000"
>
> This happens in the latest git, right?
>
> 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.
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.
It might be worth limiting the PCIGART in radeon to 32MB to see if the
lower limit helps.
Dave.
>
>
>> Is this the cause of the bug we're seeing in the report [1]?
>>
>> Anyone know what's going wrong here?
>
>
> I've attached a patch to print the debug info about the mapping
> parameters.
>
>
> diff --git a/arch/alpha/kernel/pci_iommu.c b/arch/alpha/kernel/pci_iommu.c
> index d1dbd9a..17cf0d8 100644
> --- a/arch/alpha/kernel/pci_iommu.c
> +++ b/arch/alpha/kernel/pci_iommu.c
> @@ -187,6 +187,10 @@ iommu_arena_alloc(struct device *dev, struct pci_iommu_arena *arena, long n,
> /* Search for N empty ptes */
> ptes = arena->ptes;
> mask = max(align, arena->align_entry) - 1;
> +
> + printk("%s: %p, %p, %d, %ld, %lx, %u\n", __func__, dev, arena, arena->size,
> + n, mask, align);
> +
> p = iommu_arena_find_pages(dev, arena, n, mask);
> if (p < 0) {
> spin_unlock_irqrestore(&arena->lock, flags);
>
>
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