drm/i915: Add i915_gem_object_vmap to map GEM object to virtual space

There are several places inside driver where a GEM object is mapped to
kernel virtual space. The mapping is either done for the whole object
or certain page range of it.

This patch introduces a function i915_gem_object_vmap to do such job.

v2: Use obj->pages->nents for iteration within i915_gem_object_vmap;
    break when it finishes all desired pages. The caller need to pass
    in actual page number. (Tvrtko Ursulin)

Signed-off-by: Alex Dai <yu.dai@intel.com>
Cc: Dave Gordon <david.s.gordon@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Alex Dai <yu.dai@intel.com>

drivers/gpu/drm/i915/i915_cmd_parser.c

@@ -863,37 +863,11 @@ find_reg(const struct drm_i915_reg_descriptor *table,
 static u32 *vmap_batch(struct drm_i915_gem_object *obj,
 		       unsigned start, unsigned len)
 {
-	int i;
-	void *addr = NULL;
-	struct sg_page_iter sg_iter;
 	int first_page = start >> PAGE_SHIFT;
 	int last_page = (len + start + 4095) >> PAGE_SHIFT;
 	int npages = last_page - first_page;
-	struct page **pages;
-
-	pages = drm_malloc_ab(npages, sizeof(*pages));
-	if (pages == NULL) {
-		DRM_DEBUG_DRIVER("Failed to get space for pages\n");
-		goto finish;
-	}
-
-	i = 0;
-	for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents, first_page) {
-		pages[i++] = sg_page_iter_page(&sg_iter);
-		if (i == npages)
-			break;
-	}
-
-	addr = vmap(pages, i, 0, PAGE_KERNEL);
-	if (addr == NULL) {
-		DRM_DEBUG_DRIVER("Failed to vmap pages\n");
-		goto finish;
-	}
 
-finish:
-	if (pages)
-		drm_free_large(pages);
-	return (u32*)addr;
+	return (u32*)i915_gem_object_vmap(obj, first_page, npages);
 }
 
 /* Returns a vmap'd pointer to dest_obj, which the caller must unmap */

drivers/gpu/drm/i915/i915_drv.h

@@ -2899,6 +2899,9 @@ struct drm_i915_gem_object *i915_gem_object_create_from_data(
 		struct drm_device *dev, const void *data, size_t size);
 void i915_gem_free_object(struct drm_gem_object *obj);
 void i915_gem_vma_destroy(struct i915_vma *vma);
+void *i915_gem_object_vmap(struct drm_i915_gem_object *obj,
+			   unsigned int first,
+			   unsigned int npages);
 
 /* Flags used by pin/bind&friends. */
 #define PIN_MAPPABLE	(1<<0)

drivers/gpu/drm/i915/i915_gem.c

@@ -5356,3 +5356,50 @@ i915_gem_object_create_from_data(struct drm_device *dev,
 	drm_gem_object_unreference(&obj->base);
 	return ERR_PTR(ret);
 }
+
+/**
+ * i915_gem_object_vmap - map a GEM obj into kernel virtual space
+ * @obj: the GEM obj to be mapped
+ * @first: index of the first page where mapping starts
+ * @npages: how many pages to be mapped, starting from first page
+ *
+ * Map a given page range of GEM obj into kernel virtual space. The caller must
+ * make sure the associated pages are gathered and pinned before calling this
+ * function. vunmap should be called after use.
+ *
+ * NULL will be returned if fails.
+ */
+void *i915_gem_object_vmap(struct drm_i915_gem_object *obj,
+			   unsigned int first,
+			   unsigned int npages)
+{
+	struct sg_page_iter sg_iter;
+	struct page **pages;
+	void *addr;
+	int i;
+
+	if (first + npages > obj->pages->nents) {
+		DRM_DEBUG_DRIVER("Invalid page count\n");
+		return NULL;
+	}
+
+	pages = drm_malloc_ab(npages, sizeof(*pages));
+	if (pages == NULL) {
+		DRM_DEBUG_DRIVER("Failed to get space for pages\n");
+		return NULL;
+	}
+
+	i = 0;
+	for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents, first) {
+		pages[i++] = sg_page_iter_page(&sg_iter);
+		if (i == npages)
+			break;
+	}
+
+	addr = vmap(pages, npages, 0, PAGE_KERNEL);
+	if (addr == NULL)
+		DRM_DEBUG_DRIVER("Failed to vmap pages\n");
+	drm_free_large(pages);
+
+	return addr;
+}

drivers/gpu/drm/i915/i915_gem_dmabuf.c

@@ -110,9 +110,7 @@ static void *i915_gem_dmabuf_vmap(struct dma_buf *dma_buf)
 {
 	struct drm_i915_gem_object *obj = dma_buf_to_obj(dma_buf);
 	struct drm_device *dev = obj->base.dev;
-	struct sg_page_iter sg_iter;
-	struct page **pages;
-	int ret, i;
+	int ret;
 
 	ret = i915_mutex_lock_interruptible(dev);
 	if (ret)
@@ -131,16 +129,8 @@ static void *i915_gem_dmabuf_vmap(struct dma_buf *dma_buf)
 
 	ret = -ENOMEM;
 
-	pages = drm_malloc_ab(obj->base.size >> PAGE_SHIFT, sizeof(*pages));
-	if (pages == NULL)
-		goto err_unpin;
-
-	i = 0;
-	for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents, 0)
-		pages[i++] = sg_page_iter_page(&sg_iter);
-
-	obj->dma_buf_vmapping = vmap(pages, i, 0, PAGE_KERNEL);
-	drm_free_large(pages);
+	obj->dma_buf_vmapping = i915_gem_object_vmap(obj, 0,
+			dma_buf->size >> PAGE_SHIFT);
 
 	if (!obj->dma_buf_vmapping)
 		goto err_unpin;

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -2064,27 +2064,6 @@ void intel_unpin_ringbuffer_obj(struct intel_ringbuffer *ringbuf)
 	i915_gem_object_ggtt_unpin(ringbuf->obj);
 }
 
-static u32 *vmap_obj(struct drm_i915_gem_object *obj)
-{
-	struct sg_page_iter sg_iter;
-	struct page **pages;
-	void *addr;
-	int i;
-
-	pages = drm_malloc_ab(obj->base.size >> PAGE_SHIFT, sizeof(*pages));
-	if (pages == NULL)
-		return NULL;
-
-	i = 0;
-	for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents, 0)
-		pages[i++] = sg_page_iter_page(&sg_iter);
-
-	addr = vmap(pages, i, 0, PAGE_KERNEL);
-	drm_free_large(pages);
-
-	return addr;
-}
-
 int intel_pin_and_map_ringbuffer_obj(struct drm_device *dev,
 				     struct intel_ringbuffer *ringbuf)
 {
@@ -2103,7 +2082,8 @@ int intel_pin_and_map_ringbuffer_obj(struct drm_device *dev,
 			return ret;
 		}
 
-		ringbuf->virtual_start = vmap_obj(obj);
+		ringbuf->virtual_start = i915_gem_object_vmap(obj, 0,
+				ringbuf->size >> PAGE_SHIFT);
 		if (ringbuf->virtual_start == NULL) {
 			i915_gem_object_ggtt_unpin(obj);
 			return -ENOMEM;