amd-iommu: set event buffer head and tail to 0 manually

These registers may contain values from previous kernels. So reset them
to known values before enable the event buffer again.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/arch/x86/kernel/amd_iommu_init.c b/arch/x86/kernel/amd_iommu_init.c
index 48a79b9b2f9e..068a3569f837 100644
--- a/arch/x86/kernel/amd_iommu_init.c
+++ b/arch/x86/kernel/amd_iommu_init.c
@@ -486,6 +486,10 @@ static void iommu_enable_event_buffer(struct amd_iommu *iommu)
         memcpy_toio(iommu->mmio_base + MMIO_EVT_BUF_OFFSET,
                     &entry, sizeof(entry));
 
+        /* set head and tail to zero manually */
+        writel(0x00, iommu->mmio_base + MMIO_EVT_HEAD_OFFSET);
+        writel(0x00, iommu->mmio_base + MMIO_EVT_TAIL_OFFSET);
+
         iommu_feature_enable(iommu, CONTROL_EVT_LOG_EN);
 }