linux-kernel - Re: Problems with alpha/pci + radeon/ttm

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Date:	Tue, 22 Jun 2010 18:32:36 +1000
From:	Dave Airlie <airlied@...il.com>
To:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
Cc:	mattst88@...il.com, linux-kernel@...r.kernel.org,
	linux-alpha@...r.kernel.org, rth@...ddle.net,
	ink@...assic.park.msu.ru, mcree@...on.net.nz,
	jbarnes@...tuousgeek.org, linux-pci@...r.kernel.org,
	dri-devel@...ts.freedesktop.org, alexdeucher@...il.com,
	jglisse@...hat.com
Subject: Re: Problems with alpha/pci + radeon/ttm

On Tue, Jun 22, 2010 at 3:59 PM, FUJITA Tomonori
<fujita.tomonori@....ntt.co.jp> wrote:
> On Mon, 21 Jun 2010 17:19:43 -0400
> Matt Turner <mattst88@...il.com> 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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