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SubjectRe: [BUG] agpgart-amd64 not initialized in 2.6.33-rc5 if iommu=allowed in kernel command line
From
On Sat, 23 Jan 2010 23:14:55 +0200
Marin Mitov <mitov@issp.bas.bg> wrote:

> Hi,
>
> If I start the kernel without command line parameters (4GB RAM)
> iommu-swiotlb is used due to quirk in VIA K8T800Pro Host Bridge.
> In that case all is OK.
>
> If I put in the kernel command line: iommu=allowed (+other parameters)
> I have iommu-gart used but no AGP. dmesg output:
>
> [drm:mga_do_agp_dma_bootstrap] *ERROR* Unable to acquire AGP: -19
>
> For debugging I patched the kernel (mostly prink(), shown at the end)
> producing the output in the dmesg:
>
> no command line
> MDM: agp_amd64_init entered
> MDM: agp_off: false
> MDM: agp_bridges_found: 0
> MDM: gart_iommu_aperture: 0
> MDM: agp_amd64_probe entered
>
> command line: iommu=allowed:
> MDM: gart_iommu_init
> MDM: before: no_agp = 0
> MDM: agp_amd64_init entered
> MDM: agp_off: false
> MDM: agp_bridges_found: 0
> MDM: after: no_agp = 1
> MDM: agp_amd64_init() < 0: 1
> MDM: agp_copy_info() < 0: -1
> MDM: agp_amd64_init entered
> MDM: agp_off: false
> MDM: agp_bridges_found: 0
>
> One see in the last case ( iommu=allowed) agp_amd64_init()
> is executed twice, but agp_amd64_probe() is not executed at all
> (agp_bridges_found is incremented only in agp_amd64_probe())
>
> Is this expected behavior?

Duh, it's my stupid mistake. Sorry about that.

This works for you?

Can you test this patch with set CONFIG_AGP_AMD64 to both y and m
(also loading/unloading the module twice)?

Thanks,

=
From: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Subject: [PATCH] x86/agp: fix agp_amd64_init regression

This fixes the regression introduced by the commit
42590a75019a50012f25a962246498dead428433.

The above commit changes agp_amd64_init() not to do anything if
gart_iommu_aperture is not zero.

If GART iommu calls agp_amd64_init(), we need to skip agp_amd64_init()
when it's called later via module_init.

The problem is that gart_iommu_init() calls agp_amd64_init() with not
zero gart_iommu_aperture so agp_amd64_init() is never initialized.

When gart_iommu_init() calls agp_amd64_init(), agp should be always
initialized.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
---
drivers/char/agp/amd64-agp.c | 13 +++++++++----
1 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/char/agp/amd64-agp.c b/drivers/char/agp/amd64-agp.c
index 1afb896..34cf04e 100644
--- a/drivers/char/agp/amd64-agp.c
+++ b/drivers/char/agp/amd64-agp.c
@@ -729,9 +729,6 @@ int __init agp_amd64_init(void)
if (agp_off)
return -EINVAL;

- if (gart_iommu_aperture)
- return agp_bridges_found ? 0 : -ENODEV;
-
err = pci_register_driver(&agp_amd64_pci_driver);
if (err < 0)
return err;
@@ -768,6 +765,14 @@ int __init agp_amd64_init(void)
return err;
}

+static int __init agp_amd64_mod_init(void)
+{
+ if (gart_iommu_aperture)
+ return agp_bridges_found ? 0 : -ENODEV;
+
+ return agp_amd64_init();
+}
+
static void __exit agp_amd64_cleanup(void)
{
if (gart_iommu_aperture)
@@ -777,7 +782,7 @@ static void __exit agp_amd64_cleanup(void)
pci_unregister_driver(&agp_amd64_pci_driver);
}

-module_init(agp_amd64_init);
+module_init(agp_amd64_mod_init);
module_exit(agp_amd64_cleanup);

MODULE_AUTHOR("Dave Jones <davej@redhat.com>, Andi Kleen");
--
1.5.6.5


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