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

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Message-Id: <20100627131836T.fujita.tomonori@lab.ntt.co.jp>
Date:	Sun, 27 Jun 2010 13:20:50 +0900
From:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
To:	mcree@...on.net.nz
Cc:	airlied@...il.com, fujita.tomonori@....ntt.co.jp,
	mattst88@...il.com, linux-kernel@...r.kernel.org,
	linux-alpha@...r.kernel.org, rth@...ddle.net,
	ink@...assic.park.msu.ru, 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 Thu, 24 Jun 2010 21:51:40 +1200
Michael Cree <mcree@...on.net.nz> wrote:

> >> 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 
> 0x1a312000
> [  239.281127] [drm] Tested GTT->VRAM and VRAM->GTT copy for GTT offset 
> 0x1a412000
> [  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.

Hmm, not related with IOMMU? looks like ttm_tt_populate could return
ENOMEM too. Can we locate where we hit ENOMEM first?
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