drm/msm: Fix a few comments

Fix a couple comments which had become (partially) obsolete or incorrect
with the gpuvm conversion.

Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/667237/

drivers/gpu/drm/msm/msm_gem.h

@@ -100,7 +100,7 @@ struct msm_gem_vm {
 	 *
 	 * Only used for kernel managed VMs, unused for user managed VMs.
 	 *
-	 * Protected by @mm_lock.
+	 * Protected by vm lock.  See msm_gem_lock_vm_and_obj(), for ex.
 	 */
 	struct drm_mm mm;
 

drivers/gpu/drm/msm/msm_gem_vma.c

@@ -319,13 +319,10 @@ msm_gem_vma_map(struct drm_gpuva *vma, int prot, struct sg_table *sgt)
 		mutex_lock(&vm->mmu_lock);
 
 	/*
-	 * NOTE: iommu/io-pgtable can allocate pages, so we cannot hold
+	 * NOTE: if not using pgtable preallocation, we cannot hold
 	 * a lock across map/unmap which is also used in the job_run()
 	 * path, as this can cause deadlock in job_run() vs shrinker/
 	 * reclaim.
-	 *
-	 * Revisit this if we can come up with a scheme to pre-alloc pages
-	 * for the pgtable in map/unmap ops.
 	 */
 	ret = vm_map_op(vm, &(struct msm_vm_map_op){
 		.iova = vma->va.addr,