From: Kai-Heng Feng <kai.heng.feng@canonical.com>
To: joro@8bytes.org
Cc: iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
Kai-Heng Feng <kai.heng.feng@canonical.com>,
Alex Deucher <alexander.deucher@amd.com>
Subject: [PATCH v2] iommu/amd: Disable IOMMU on Stoney Ridge systems
Date: Fri, 29 Nov 2019 22:21:54 +0800 [thread overview]
Message-ID: <20191129142154.29658-1-kai.heng.feng@canonical.com> (raw)
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.deucher@amd.com>
Bug: https://gitlab.freedesktop.org/drm/amd/issues/961
Signed-off-by: Kai-Heng Feng <kai.heng.feng@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
next reply other threads:[~2019-11-29 14:22 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-29 14:21 Kai-Heng Feng [this message]
2019-12-01 12:42 ` [PATCH v2] iommu/amd: Disable IOMMU on Stoney Ridge systems Lucas Stach
2019-12-02 16:36 ` Deucher, Alexander
2019-12-04 16:08 ` Deucher, Alexander
2019-12-06 5:59 ` Kai-Heng Feng
2019-12-06 8:57 ` Christian König
2019-12-02 17:00 ` Christoph Hellwig
2019-12-06 5:57 ` Kai-Heng Feng
2019-12-17 9:53 ` Joerg Roedel
2019-12-18 17:45 ` Kai-Heng Feng
2019-12-19 19:15 ` Deucher, Alexander
2019-12-20 2:13 ` Kai-Heng Feng
2020-01-06 8:37 ` Kai-Heng Feng
2020-02-05 10:10 ` Kai-Heng Feng
2020-02-05 13:24 ` Joerg Roedel
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