iommu/amd: Add workaround for event log erratum

commit 3d06fca8d2aa3543030e40b95f1d62f9f5a03540 upstream.

Due to a recent erratum it can happen that the head pointer
of the event-log is updated before the actual event-log
entry is written. This patch implements the recommended
workaround.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 966a6e7..f1d5408 100644 (file)
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -381,12 +381,27 @@ static void dump_command(unsigned long phys_addr)
 
 static void iommu_print_event(struct amd_iommu *iommu, void *__evt)
 {
-       u32 *event = __evt;
-       int type  = (event[1] >> EVENT_TYPE_SHIFT)  & EVENT_TYPE_MASK;
-       int devid = (event[0] >> EVENT_DEVID_SHIFT) & EVENT_DEVID_MASK;
-       int domid = (event[1] >> EVENT_DOMID_SHIFT) & EVENT_DOMID_MASK;
-       int flags = (event[1] >> EVENT_FLAGS_SHIFT) & EVENT_FLAGS_MASK;
-       u64 address = (u64)(((u64)event[3]) << 32) | event[2];
+       int type, devid, domid, flags;
+       volatile u32 *event = __evt;
+       int count = 0;
+       u64 address;
+
+retry:
+       type    = (event[1] >> EVENT_TYPE_SHIFT)  & EVENT_TYPE_MASK;
+       devid   = (event[0] >> EVENT_DEVID_SHIFT) & EVENT_DEVID_MASK;
+       domid   = (event[1] >> EVENT_DOMID_SHIFT) & EVENT_DOMID_MASK;
+       flags   = (event[1] >> EVENT_FLAGS_SHIFT) & EVENT_FLAGS_MASK;
+       address = (u64)(((u64)event[3]) << 32) | event[2];
+
+       if (type == 0) {
+               /* Did we hit the erratum? */
+               if (++count == LOOP_TIMEOUT) {
+                       pr_err("AMD-Vi: No event written to event log\n");
+                       return;
+               }
+               udelay(1);
+               goto retry;
+       }
 
        printk(KERN_ERR "AMD-Vi: Event logged [");
 
@@ -439,6 +454,8 @@ static void iommu_print_event(struct amd_iommu *iommu, void *__evt)
        default:
                printk(KERN_ERR "UNKNOWN type=0x%02x]\n", type);
        }
+
+       memset(__evt, 0, 4 * sizeof(u32));
 }
 
 static void iommu_poll_events(struct amd_iommu *iommu)