drm: Introduce an iterator over holes in the drm_mm range manager

This will be used i915 in forthcoming patches in order to measure the
largest contiguous chunk of memory available for enabling chipset
features.

v2: Try to make the macro marginally safer and more readable by not
depending upon the drm_mm_hole_node_end() being non-zero. Note that we
need to open code list_for_each() in order to update the hole_start,
hole_end variable on each iteration and keep the macro sane.

v3: Tidy up few BUG_ONs that fell foul of adding additional tests to
drm_mm_hole_node_start().

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Dave Airlie <airlied@redhat.com>
Acked-by: Dave Airlie <airlied@redhat.com>
Cc: dri-devel@lists.freedesktop.org
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

2 files changed, 57 insertions, 41 deletions

diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c
index bd203b61a72b..b751b8e1e205 100644
--- a/drivers/gpu/drm/drm_mm.c
+++ b/drivers/gpu/drm/drm_mm.c
@@ -102,20 +102,6 @@ int drm_mm_pre_get(struct drm_mm *mm)
 }
 EXPORT_SYMBOL(drm_mm_pre_get);
 
-static inline unsigned long drm_mm_hole_node_start(struct drm_mm_node *hole_node)
-{
-        return hole_node->start + hole_node->size;
-}
-
-static inline unsigned long drm_mm_hole_node_end(struct drm_mm_node *hole_node)
-{
-        struct drm_mm_node *next_node =
-                list_entry(hole_node->node_list.next, struct drm_mm_node,
-                           node_list);
-
-        return next_node->start;
-}
-
 static void drm_mm_insert_helper(struct drm_mm_node *hole_node,
                                  struct drm_mm_node *node,
                                  unsigned long size, unsigned alignment,
@@ -127,7 +113,7 @@ static void drm_mm_insert_helper(struct drm_mm_node *hole_node,
         unsigned long adj_start = hole_start;
         unsigned long adj_end = hole_end;
 
-        BUG_ON(!hole_node->hole_follows || node->allocated);
+        BUG_ON(node->allocated);
 
         if (mm->color_adjust)
                 mm->color_adjust(hole_node, color, &adj_start, &adj_end);
@@ -155,7 +141,7 @@ static void drm_mm_insert_helper(struct drm_mm_node *hole_node,
         BUG_ON(node->start + node->size > adj_end);
 
         node->hole_follows = 0;
-        if (node->start + node->size < hole_end) {
+        if (__drm_mm_hole_node_start(node) < hole_end) {
                 list_add(&node->hole_stack, &mm->hole_stack);
                 node->hole_follows = 1;
         }
@@ -168,15 +154,10 @@ struct drm_mm_node *drm_mm_create_block(struct drm_mm *mm,
 {
         struct drm_mm_node *hole, *node;
         unsigned long end = start + size;
+        unsigned long hole_start;
+        unsigned long hole_end;
 
-        list_for_each_entry(hole, &mm->hole_stack, hole_stack) {
-                unsigned long hole_start;
-                unsigned long hole_end;
-
-                BUG_ON(!hole->hole_follows);
-                hole_start = drm_mm_hole_node_start(hole);
-                hole_end = drm_mm_hole_node_end(hole);
-
+        drm_mm_for_each_hole(hole, mm, hole_start, hole_end) {
                 if (hole_start > start || hole_end < end)
                         continue;
 
@@ -293,7 +274,7 @@ static void drm_mm_insert_helper_range(struct drm_mm_node *hole_node,
         BUG_ON(node->start + node->size > end);
 
         node->hole_follows = 0;
-        if (node->start + node->size < hole_end) {
+        if (__drm_mm_hole_node_start(node) < hole_end) {
                 list_add(&node->hole_stack, &mm->hole_stack);
                 node->hole_follows = 1;
         }
@@ -358,12 +339,13 @@ void drm_mm_remove_node(struct drm_mm_node *node)
             list_entry(node->node_list.prev, struct drm_mm_node, node_list);
 
         if (node->hole_follows) {
-                BUG_ON(drm_mm_hole_node_start(node)
-                                == drm_mm_hole_node_end(node));
+                BUG_ON(__drm_mm_hole_node_start(node) ==
+                       __drm_mm_hole_node_end(node));
                 list_del(&node->hole_stack);
         } else
-                BUG_ON(drm_mm_hole_node_start(node)
-                                != drm_mm_hole_node_end(node));
+                BUG_ON(__drm_mm_hole_node_start(node) !=
+                       __drm_mm_hole_node_end(node));
+
 
         if (!prev_node->hole_follows) {
                 prev_node->hole_follows = 1;
@@ -421,6 +403,8 @@ struct drm_mm_node *drm_mm_search_free_generic(const struct drm_mm *mm,
 {
         struct drm_mm_node *entry;
         struct drm_mm_node *best;
+        unsigned long adj_start;
+        unsigned long adj_end;
         unsigned long best_size;
 
         BUG_ON(mm->scanned_blocks);
@@ -428,17 +412,13 @@ struct drm_mm_node *drm_mm_search_free_generic(const struct drm_mm *mm,
         best = NULL;
         best_size = ~0UL;
 
-        list_for_each_entry(entry, &mm->hole_stack, hole_stack) {
-                unsigned long adj_start = drm_mm_hole_node_start(entry);
-                unsigned long adj_end = drm_mm_hole_node_end(entry);
-
+        drm_mm_for_each_hole(entry, mm, adj_start, adj_end) {
                 if (mm->color_adjust) {
                         mm->color_adjust(entry, color, &adj_start, &adj_end);
                         if (adj_end <= adj_start)
                                 continue;
                 }
 
-                BUG_ON(!entry->hole_follows);
                 if (!check_free_hole(adj_start, adj_end, size, alignment))
                         continue;
 
@@ -465,6 +445,8 @@ struct drm_mm_node *drm_mm_search_free_in_range_generic(const struct drm_mm *mm,
 {
         struct drm_mm_node *entry;
         struct drm_mm_node *best;
+        unsigned long adj_start;
+        unsigned long adj_end;
         unsigned long best_size;
 
         BUG_ON(mm->scanned_blocks);
@@ -472,13 +454,11 @@ struct drm_mm_node *drm_mm_search_free_in_range_generic(const struct drm_mm *mm,
         best = NULL;
         best_size = ~0UL;
 
-        list_for_each_entry(entry, &mm->hole_stack, hole_stack) {
-                unsigned long adj_start = drm_mm_hole_node_start(entry) < start ?
-                        start : drm_mm_hole_node_start(entry);
-                unsigned long adj_end = drm_mm_hole_node_end(entry) > end ?
-                        end : drm_mm_hole_node_end(entry);
-
-                BUG_ON(!entry->hole_follows);
+        drm_mm_for_each_hole(entry, mm, adj_start, adj_end) {
+                if (adj_start < start)
+                        adj_start = start;
+                if (adj_end > end)
+                        adj_end = end;
 
                 if (mm->color_adjust) {
                         mm->color_adjust(entry, color, &adj_start, &adj_end);
diff --git a/include/drm/drm_mm.h b/include/drm/drm_mm.h
index 4020f9661c3c..cd453653f634 100644
--- a/include/drm/drm_mm.h
+++ b/include/drm/drm_mm.h
@@ -89,6 +89,29 @@ static inline bool drm_mm_initialized(struct drm_mm *mm)
 {
         return mm->hole_stack.next;
 }
+
+static inline unsigned long __drm_mm_hole_node_start(struct drm_mm_node *hole_node)
+{
+        return hole_node->start + hole_node->size;
+}
+
+static inline unsigned long drm_mm_hole_node_start(struct drm_mm_node *hole_node)
+{
+        BUG_ON(!hole_node->hole_follows);
+        return __drm_mm_hole_node_start(hole_node);
+}
+
+static inline unsigned long __drm_mm_hole_node_end(struct drm_mm_node *hole_node)
+{
+        return list_entry(hole_node->node_list.next,
+                          struct drm_mm_node, node_list)->start;
+}
+
+static inline unsigned long drm_mm_hole_node_end(struct drm_mm_node *hole_node)
+{
+        return __drm_mm_hole_node_end(hole_node);
+}
+
 #define drm_mm_for_each_node(entry, mm) list_for_each_entry(entry, \
                                                 &(mm)->head_node.node_list, \
                                                 node_list)
@@ -99,6 +122,19 @@ static inline bool drm_mm_initialized(struct drm_mm *mm)
              entry != NULL; entry = next, \
                 next = entry ? list_entry(entry->node_list.next, \
                         struct drm_mm_node, node_list) : NULL) \
+
+/* Note that we need to unroll list_for_each_entry in order to inline
+ * setting hole_start and hole_end on each iteration and keep the
+ * macro sane.
+ */
+#define drm_mm_for_each_hole(entry, mm, hole_start, hole_end) \
+        for (entry = list_entry((mm)->hole_stack.next, struct drm_mm_node, hole_stack); \
+             &entry->hole_stack != &(mm)->hole_stack ? \
+             hole_start = drm_mm_hole_node_start(entry), \
+             hole_end = drm_mm_hole_node_end(entry), \
+             1 : 0; \
+             entry = list_entry(entry->hole_stack.next, struct drm_mm_node, hole_stack))
+
 /*
  * Basic range manager support (drm_mm.c)
  */