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>

diff --git a/arch/x86/kernel/amd_iommu_init.c b/arch/x86/kernel/amd_iommu_init.c
index 48a79b9b2f9ee3a0b1e4025452b0a99f1486896c..068a3569f8375d1fd8d863585040a23be425c132 100644 (file)
--- 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);
 }