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x86/gart: Check for GART support before accessing GART registers

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GART registers are not present in newer AMD processors (Fam15h, Model
10h and later). So, avoid accessing those in PCI config space by
returning early in early_gart_iommu_check() and gart_iommu_hole_init()
if GART is not available.

Current code doesn't break on existing processors but there are some
side effects:

We get bogus AGP aperture messages which are simply noise on
GART-less processors:

  AGP: Node 0: aperture [bus addr 0x00000000-0x01ffffff] (32MB)
  AGP: Your BIOS doesn't leave aperture memory hole
  AGP: Please enable the IOMMU option in the BIOS setup
  AGP: This costs you 64MB of RAM
  AGP: Mapping aperture over RAM [mem 0xd4000000-0xd7ffffff]

We can avoid calling allocate_aperture() and would not have to
wastefully reserve 64MB of RAM with memblock_reserve(). Also, we can
avoid having to loop through all PCI buses and devices twice, searching
for a non-existent AGP bridge if we bail out early.

Refactor the family check used in amd_nb.c into an inline function so we
can use it here as well as in amd_nb.c

Fix some typos while at it.

Tested the patch on Fam10h and Fam15h Model 00h-fh and this code runs
fine. On Fam15h Model 60h-6fh and on Fam16h, we bail early as they don't
have GART.

Signed-off-by: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Joerg Rodel <joro@8bytes.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1428443197-3834-1-git-send-email-Aravind.Gopalakrishnan@amd.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Aravind Gopalakrishnan 2015-04-07 16:46:37 -05:00 committed by Ingo Molnar
parent 5198b44374
commit 1b4574292e
3 changed files with 19 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
arch/x86/include/asm/amd_nb.h
View File

@ -98,11 +98,22 @@ static inline u16 amd_get_node_id(struct pci_dev *pdev)
return 0;
}
static inline bool amd_gart_present(void)
{
/* GART present only on Fam15h, upto model 0fh */
if (boot_cpu_data.x86 == 0xf || boot_cpu_data.x86 == 0x10 ||
(boot_cpu_data.x86 == 0x15 && boot_cpu_data.x86_model < 0x10))
return true;
return false;
}
#else
#define amd_nb_num(x) 0
#define amd_nb_has_feature(x) false
#define node_to_amd_nb(x) NULL
#define amd_gart_present(x) false
#endif

4
arch/x86/kernel/amd_nb.c
View File

@ -89,9 +89,7 @@ int amd_cache_northbridges(void)
next_northbridge(link, amd_nb_link_ids);
}
/* GART present only on Fam15h upto model 0fh */
if (boot_cpu_data.x86 == 0xf || boot_cpu_data.x86 == 0x10 ||
(boot_cpu_data.x86 == 0x15 && boot_cpu_data.x86_model < 0x10))
if (amd_gart_present())
amd_northbridges.flags |= AMD_NB_GART;
/*

8
arch/x86/kernel/aperture_64.c
View File

@ -262,6 +262,9 @@ void __init early_gart_iommu_check(void)
u64 aper_base = 0, last_aper_base = 0;
int aper_enabled = 0, last_aper_enabled = 0, last_valid = 0;
if (!amd_gart_present())
return;
if (!early_pci_allowed())
return;
@ -355,6 +358,9 @@ int __init gart_iommu_hole_init(void)
int fix, slot, valid_agp = 0;
int i, node;
if (!amd_gart_present())
return -ENODEV;
if (gart_iommu_aperture_disabled || !fix_aperture ||
!early_pci_allowed())
return -ENODEV;
@ -452,7 +458,7 @@ out:
force_iommu ||
valid_agp ||
fallback_aper_force) {
pr_info("Your BIOS doesn't leave a aperture memory hole\n");
pr_info("Your BIOS doesn't leave an aperture memory hole\n");
pr_info("Please enable the IOMMU option in the BIOS setup\n");
pr_info("This costs you %dMB of RAM\n",
32 << fallback_aper_order);