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authorKai-Heng Feng <kai.heng.feng@canonical.com>2020-02-10 15:51:15 +0800
committerJoerg Roedel <jroedel@suse.de>2020-02-19 11:08:24 +0100
commit3dfee47b215e49788cfc80e474820ea2e948c031 (patch)
tree7a62c604676e9d80175e6f10c5125b08f0a43845
parent1ddb32da4a629fa7f87873d0b6836c2e1feb7518 (diff)
iommu/amd: Disable IOMMU on Stoney Ridge systems
Serious screen flickering when Stoney Ridge outputs to a 4K monitor. Use identity-mapping and PCI ATS doesn't help this issue. 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.deucher@amd.com> Bug: https://gitlab.freedesktop.org/drm/amd/issues/961 Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com> Acked-by: Alex Deucher <alexander.deucher@amd.com> Signed-off-by: Joerg Roedel <jroedel@suse.de>
-rw-r--r--drivers/iommu/amd_iommu_init.c13
1 files changed, 12 insertions, 1 deletions
diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c
index 2759a8d57b7f..6be3853a5d97 100644
--- a/drivers/iommu/amd_iommu_init.c
+++ b/drivers/iommu/amd_iommu_init.c
@@ -2523,6 +2523,7 @@ 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;
@@ -2610,6 +2611,16 @@ 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();
@@ -2718,7 +2729,7 @@ 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;
}