Serious screen flickering when Stoney Ridge outputs to a 4K monitor. According to Alex Deucher, IOMMU isn't enabled on Windows, so let's do the same here to avoid screen flickering on 4K monitor.
Cc: Alex Deucher <alexander.deuc...@amd.com> Bug: https://gitlab.freedesktop.org/drm/amd/issues/961 Signed-off-by: Kai-Heng Feng <kai.heng.f...@canonical.com> --- v2: - Find Stoney graphics instead of host bridge. drivers/iommu/amd_iommu_init.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c index 568c52317757..139aa6fdadda 100644 --- a/drivers/iommu/amd_iommu_init.c +++ b/drivers/iommu/amd_iommu_init.c @@ -2516,6 +2516,7 @@ static int __init early_amd_iommu_init(void) struct acpi_table_header *ivrs_base; acpi_status status; int i, remap_cache_sz, ret = 0; + u32 pci_id; if (!amd_iommu_detected) return -ENODEV; @@ -2603,6 +2604,16 @@ static int __init early_amd_iommu_init(void) if (ret) goto out; + /* Disable IOMMU if there's Stoney Ridge graphics */ + for (i = 0; i < 32; i++) { + pci_id = read_pci_config(0, i, 0, 0); + if ((pci_id & 0xffff) == 0x1002 && (pci_id >> 16) == 0x98e4) { + pr_info("Disable IOMMU on Stoney Ridge\n"); + amd_iommu_disabled = true; + break; + } + } + /* Disable any previously enabled IOMMUs */ if (!is_kdump_kernel() || amd_iommu_disabled) disable_iommus(); @@ -2711,7 +2722,7 @@ static int __init state_next(void) ret = early_amd_iommu_init(); init_state = ret ? IOMMU_INIT_ERROR : IOMMU_ACPI_FINISHED; if (init_state == IOMMU_ACPI_FINISHED && amd_iommu_disabled) { - pr_info("AMD IOMMU disabled on kernel command-line\n"); + pr_info("AMD IOMMU disabled\n"); init_state = IOMMU_CMDLINE_DISABLED; ret = -EINVAL; } -- 2.17.1 _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
