iommu/amd: Update event log pointer as soon as processing is complete

Update event buffer head pointer once driver completes processing. So
that IOMMU can write new log without waiting for driver to complete
processing all event logs.
Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
Reviewed-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Link: https://lore.kernel.org/r/20240828111029.5429-2-vasant.hegde@amd.comSigned-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/amd/iommu.c

@@ -825,10 +825,12 @@ static void iommu_poll_events(struct amd_iommu *iommu)
 
 	while (head != tail) {
 		iommu_print_event(iommu, iommu->evt_buf + head);
+
+		/* Update head pointer of hardware ring-buffer */
 		head = (head + EVENT_ENTRY_SIZE) % EVT_BUFFER_SIZE;
+		writel(head, iommu->mmio_base + MMIO_EVT_HEAD_OFFSET);
 	}
 
-	writel(head, iommu->mmio_base + MMIO_EVT_HEAD_OFFSET);
 }
 
 #ifdef CONFIG_IRQ_REMAP