On Thu, Apr 02, 2015 at 12:04:21PM -0500, Aravind Gopalakrishnan wrote: > >No need - I can amend the local copy I have here.
Here's what I did: --- From: Aravind Gopalakrishnan <aravind.gopalakrish...@amd.com> Date: Wed, 1 Apr 2015 09:32:08 -0500 Subject: [PATCH] x86/gart: Check for GART support before accessing GART registers MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit GART registers are not present in newer AMD processors (Fam15h, Model 10h and later). So, avoid accesses to GART registers 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 a 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 into an inline function so we can use it here as well as in amd_nb.c. Tested the patch on Fam10h and Fam15h Model 00h-fh and this code runs fine. On Fam15h, Models 60h-6fh and on Fam16h, we bail out early as they don't have a GART. Signed-off-by: Aravind Gopalakrishnan <aravind.gopalakrish...@amd.com> Reviewed-by: Suravee Suthikulpanit <suravee.suthikulpa...@amd.com> Cc: Jörg Rödel <j...@8bytes.org> Cc: Thomas Gleixner <t...@linutronix.de> Cc: Ingo Molnar <mi...@kernel.org> Cc: H. Peter Anvin <h...@zytor.com> Cc: Bjorn Helgaas <bhelg...@google.com> Cc: x86-ml <x...@kernel.org> Link: http://lkml.kernel.org/r/1427898728-3434-1-git-send-email-aravind.gopalakrish...@amd.com Signed-off-by: --- arch/x86/include/asm/amd_nb.h | 11 +++++++++++ arch/x86/kernel/amd_nb.c | 4 +--- arch/x86/kernel/aperture_64.c | 4 ++-- 3 files changed, 14 insertions(+), 5 deletions(-) diff --git a/arch/x86/include/asm/amd_nb.h b/arch/x86/include/asm/amd_nb.h index aaac3b2fb746..864c8bd8cbe4 100644 --- a/arch/x86/include/asm/amd_nb.h +++ b/arch/x86/include/asm/amd_nb.h @@ -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 diff --git a/arch/x86/kernel/amd_nb.c b/arch/x86/kernel/amd_nb.c index 5caed1dd7ccf..29fa475ec518 100644 --- a/arch/x86/kernel/amd_nb.c +++ b/arch/x86/kernel/amd_nb.c @@ -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; /* diff --git a/arch/x86/kernel/aperture_64.c b/arch/x86/kernel/aperture_64.c index 76164e173a24..1cb170b06853 100644 --- a/arch/x86/kernel/aperture_64.c +++ b/arch/x86/kernel/aperture_64.c @@ -262,7 +262,7 @@ 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 (!early_pci_allowed()) + if (!early_pci_allowed() || !amd_gart_present()) return; /* This is mostly duplicate of iommu_hole_init */ @@ -356,7 +356,7 @@ int __init gart_iommu_hole_init(void) int i, node; if (gart_iommu_aperture_disabled || !fix_aperture || - !early_pci_allowed()) + !early_pci_allowed() || !amd_gart_present()) return -ENODEV; pr_info("Checking aperture...\n"); -- 2.3.3 -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
