• Aravind Gopalakrishnan's avatar
    x86/gart: Check for GART support before accessing GART registers · 1b457429
    Aravind Gopalakrishnan authored
    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: default avatarAravind Gopalakrishnan <Aravind.Gopalakrishnan@amd.com>
    Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
    Reviewed-by: default avatarSuravee 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: default avatarIngo Molnar <mingo@kernel.org>
amd_nb.h 2.56 KB