From: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
To: mitov@issp.bas.bg
Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de,
mingo@redhat.com, hpa@zytor.com
Subject: Re: [BUG] agpgart-amd64 not initialized in 2.6.33-rc2
Date: Mon, 28 Dec 2009 15:37:33 +0900 [thread overview]
Message-ID: <20091228153704Z.fujita.tomonori@lab.ntt.co.jp> (raw)
In-Reply-To: <200912271719.39306.mitov@issp.bas.bg>
On Sun, 27 Dec 2009 17:19:39 +0200
Marin Mitov <mitov@issp.bas.bg> wrote:
> Hi all,
>
> Recently (2.6.33-rc2 kernel, x86_64, 4GB RAM) I found (in dmesg):
>
> [drm:mga_do_agp_dma_bootstrap] *ERROR* Unable to acquire AGP: -19
>
> and there is no /dev/agpgart device on the machine while all is OK
> if booting 2.6.32.2.
>
> In both kernels I have:
>
> CONFIG_AGP=y
> CONFIG_AGP_AMD64=y
>
> CONFIG_GART_IOMMU=y
>
> but nevertheless dmesg shows:
>
> PCI-DMA: Using software bounce buffering for IO (SWIOTLB)
>
> due to quirks in via K8T800Pro host bridge.
>
> Looking for the reason I found that agp_amd64_init() appears in:
>
> #ifndef CONFIG_GART_IOMMU
> module_init(agp_amd64_init);
> module_exit(agp_amd64_cleanup);
> #endif
>
> /* so it is not invoked here due to CONFIG_GART_IOMMU=y */
>
> and also appears in:
>
> arch/x86/kernel/pci-gart_64.c, function: gart_iommu_init()
>
> The last one is part of the struct x86_init_ops(struct x86_init_iommu, as a function pointer)
> only if gart-iommu is successfully detected, which is not the case here due to the quirk,
> so agp_amd64_init() is not invoked here neither.
>
> Sure, configuring the kernel without CONFIG_GART_IOMMU=y (which is not user selectable)
>
> should solve the problem, but usually users do not know about quirks, so it should
> work even as set here (and it works up to 2.6.32.2). I believe the bug is introduced
> with the changes in the order iommu detect/init works for 2.6.33.
>
> I am here for additional info/tests.
Sorry about the regression. Does this works?
Thanks,
diff --git a/drivers/char/agp/amd64-agp.c b/drivers/char/agp/amd64-agp.c
index 2fb2e6c..5aa7a58 100644
--- a/drivers/char/agp/amd64-agp.c
+++ b/drivers/char/agp/amd64-agp.c
@@ -725,9 +725,14 @@ static struct pci_driver agp_amd64_pci_driver = {
int __init agp_amd64_init(void)
{
int err = 0;
+ static int done = 0;
if (agp_off)
return -EINVAL;
+
+ if (done++)
+ return agp_bridges_found ? 0 : -ENODEV;
+
err = pci_register_driver(&agp_amd64_pci_driver);
if (err < 0)
return err;
@@ -771,12 +776,8 @@ static void __exit agp_amd64_cleanup(void)
pci_unregister_driver(&agp_amd64_pci_driver);
}
-/* On AMD64 the PCI driver needs to initialize this driver early
- for the IOMMU, so it has to be called via a backdoor. */
-#ifndef CONFIG_GART_IOMMU
module_init(agp_amd64_init);
module_exit(agp_amd64_cleanup);
-#endif
MODULE_AUTHOR("Dave Jones <davej@redhat.com>, Andi Kleen");
module_param(agp_try_unsupported, bool, 0);
next prev parent reply other threads:[~2009-12-28 6:38 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-12-27 15:19 [BUG] agpgart-amd64 not initialized in 2.6.33-rc2 Marin Mitov
2009-12-28 6:37 ` FUJITA Tomonori [this message]
2009-12-28 7:18 ` Marin Mitov
2009-12-28 8:10 ` Ingo Molnar
2009-12-28 9:11 ` FUJITA Tomonori
2009-12-30 12:21 ` [tip:x86/urgent] x86/agp: Fix agp_amd64_init() initialization with CONFIG_GART_IOMMU enabled tip-bot for FUJITA Tomonori
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