drm/i915: extend i915_vma_pin_iomap()

In the future display might try call this with a normal smem object,
which doesn't require PIN_MAPPABLE underneath in order to CPU map the
pages (unlike stolen).  Extend i915_vma_pin_iomap() to directly use
i915_gem_object_pin_map() for such cases.

This change was suggested by Chris P Wilson, that we pin
the smem with i915_gem_object_pin_map_unlocked().

v2 (jheikkil): Change i915_gem_object_pin_map_unlocked to
               i915_gem_object_pin_map
Signed-off-by: CQ Tang <cq.tang@intel.com>
Signed-off-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
Cc: Chris Wilson <chris.p.wilson@intel.com>
Cc: Jari Tahvanainen <jari.tahvanainen@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
[mauld: tweak commit message, plus minor checkpatch fix]
Link: https://patchwork.freedesktop.org/patch/msgid/20220610121205.29645-2-juhapekka.heikkila@gmail.com

drivers/gpu/drm/i915/i915_vma.c

@@ -551,13 +551,6 @@ void __iomem *i915_vma_pin_iomap(struct i915_vma *vma)
 	if (WARN_ON_ONCE(vma->obj->flags & I915_BO_ALLOC_GPU_ONLY))
 		return IOMEM_ERR_PTR(-EINVAL);
 
-	if (!i915_gem_object_is_lmem(vma->obj)) {
-		if (GEM_WARN_ON(!i915_vma_is_map_and_fenceable(vma))) {
-			err = -ENODEV;
-			goto err;
-		}
-	}
-
 	GEM_BUG_ON(!i915_vma_is_ggtt(vma));
 	GEM_BUG_ON(!i915_vma_is_bound(vma, I915_VMA_GLOBAL_BIND));
 	GEM_BUG_ON(i915_vma_verify_bind_complete(vma));
@@ -570,20 +563,33 @@ void __iomem *i915_vma_pin_iomap(struct i915_vma *vma)
 		 * of pages, that way we can also drop the
 		 * I915_BO_ALLOC_CONTIGUOUS when allocating the object.
 		 */
-		if (i915_gem_object_is_lmem(vma->obj))
+		if (i915_gem_object_is_lmem(vma->obj)) {
 			ptr = i915_gem_object_lmem_io_map(vma->obj, 0,
 							  vma->obj->base.size);
-		else
+		} else if (i915_vma_is_map_and_fenceable(vma)) {
 			ptr = io_mapping_map_wc(&i915_vm_to_ggtt(vma->vm)->iomap,
 						vma->node.start,
 						vma->node.size);
+		} else {
+			ptr = (void __iomem *)
+				i915_gem_object_pin_map(vma->obj, I915_MAP_WC);
+			if (IS_ERR(ptr)) {
+				err = PTR_ERR(ptr);
+				goto err;
+			}
+			ptr = page_pack_bits(ptr, 1);
+		}
+
 		if (ptr == NULL) {
 			err = -ENOMEM;
 			goto err;
 		}
 
 		if (unlikely(cmpxchg(&vma->iomap, NULL, ptr))) {
-			io_mapping_unmap(ptr);
+			if (page_unmask_bits(ptr))
+				__i915_gem_object_release_map(vma->obj);
+			else
+				io_mapping_unmap(ptr);
 			ptr = vma->iomap;
 		}
 	}
@@ -597,7 +603,7 @@ void __iomem *i915_vma_pin_iomap(struct i915_vma *vma)
 	i915_vma_set_ggtt_write(vma);
 
 	/* NB Access through the GTT requires the device to be awake. */
-	return ptr;
+	return page_mask_bits(ptr);
 
 err_unpin:
 	__i915_vma_unpin(vma);
@@ -615,6 +621,8 @@ void i915_vma_unpin_iomap(struct i915_vma *vma)
 {
 	GEM_BUG_ON(vma->iomap == NULL);
 
+	/* XXX We keep the mapping until __i915_vma_unbind()/evict() */
+
 	i915_vma_flush_writes(vma);
 
 	i915_vma_unpin_fence(vma);
@@ -1763,7 +1771,10 @@ static void __i915_vma_iounmap(struct i915_vma *vma)
 	if (vma->iomap == NULL)
 		return;
 
-	io_mapping_unmap(vma->iomap);
+	if (page_unmask_bits(vma->iomap))
+		__i915_gem_object_release_map(vma->obj);
+	else
+		io_mapping_unmap(vma->iomap);
 	vma->iomap = NULL;
 }