1 files changed, 34 insertions, 0 deletions

diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c
index 81837b0710a9..faf10ba1ed9a 100644
--- a/drivers/iommu/amd_iommu_init.c
+++ b/drivers/iommu/amd_iommu_init.c
@@ -975,6 +975,38 @@ static void __init free_iommu_all(void)
 }
 
 /*
+ * Family15h Model 10h-1fh erratum 746 (IOMMU Logging May Stall Translations)
+ * Workaround:
+ *     BIOS should disable L2B micellaneous clock gating by setting
+ *     L2_L2B_CK_GATE_CONTROL[CKGateL2BMiscDisable](D0F2xF4_x90[2]) = 1b
+ */
+static void __init amd_iommu_erratum_746_workaround(struct amd_iommu *iommu)
+{
+        u32 value;
+
+        if ((boot_cpu_data.x86 != 0x15) ||
+            (boot_cpu_data.x86_model < 0x10) ||
+            (boot_cpu_data.x86_model > 0x1f))
+                return;
+
+        pci_write_config_dword(iommu->dev, 0xf0, 0x90);
+        pci_read_config_dword(iommu->dev, 0xf4, &value);
+
+        if (value & BIT(2))
+                return;
+
+        /* Select NB indirect register 0x90 and enable writing */
+        pci_write_config_dword(iommu->dev, 0xf0, 0x90 | (1 << 8));
+
+        pci_write_config_dword(iommu->dev, 0xf4, value | 0x4);
+        pr_info("AMD-Vi: Applying erratum 746 workaround for IOMMU at %s\n",
+                dev_name(&iommu->dev->dev));
+
+        /* Clear the enable writing bit */
+        pci_write_config_dword(iommu->dev, 0xf0, 0x90);
+}
+
+/*
  * This function clues the initialization function for one IOMMU
  * together and also allocates the command buffer and programs the
  * hardware. It does NOT enable the IOMMU. This is done afterwards.
@@ -1172,6 +1204,8 @@ static int iommu_init_pci(struct amd_iommu *iommu)
                         iommu->stored_l2[i] = iommu_read_l2(iommu, i);
         }
 
+        amd_iommu_erratum_746_workaround(iommu);
+
         return pci_enable_device(iommu->dev);
 }