drm/i915: combine all small integers into one single bitfield

This saves a whooping 7 dwords. Zero functional changes. Because
some of the refcounts are rather tightly calculated, I've put
BUG_ONs in the code to check for overflows.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Eric Anholt <eric@anholt.net>

2 files changed, 54 insertions, 26 deletions

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 91b3a1c20ef8..cccf8019f65a 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -658,19 +658,64 @@ struct drm_i915_gem_object {
          * (has pending rendering), and is not set if it's on inactive (ready
          * to be unbound).
          */
-        int active;
+        unsigned int active : 1;
 
         /**
          * This is set if the object has been written to since last bound
          * to the GTT
          */
-        int dirty;
+        unsigned int dirty : 1;
+
+        /**
+         * Fence register bits (if any) for this object.  Will be set
+         * as needed when mapped into the GTT.
+         * Protected by dev->struct_mutex.
+         *
+         * Size: 4 bits for 16 fences + sign (for FENCE_REG_NONE)
+         */
+        int fence_reg : 5;
+
+        /**
+         * Used for checking the object doesn't appear more than once
+         * in an execbuffer object list.
+         */
+        unsigned int in_execbuffer : 1;
+
+        /**
+         * Advice: are the backing pages purgeable?
+         */
+        unsigned int madv : 2;
+
+        /**
+         * Refcount for the pages array. With the current locking scheme, there
+         * are at most two concurrent users: Binding a bo to the gtt and
+         * pwrite/pread using physical addresses. So two bits for a maximum
+         * of two users are enough.
+         */
+        unsigned int pages_refcount : 2;
+#define DRM_I915_GEM_OBJECT_MAX_PAGES_REFCOUNT 0x3
+
+        /**
+         * Current tiling mode for the object.
+         */
+        unsigned int tiling_mode : 2;
+
+        /** How many users have pinned this object in GTT space. The following
+         * users can each hold at most one reference: pwrite/pread, pin_ioctl
+         * (via user_pin_count), execbuffer (objects are not allowed multiple
+         * times for the same batchbuffer), and the framebuffer code. When
+         * switching/pageflipping, the framebuffer code has at most two buffers
+         * pinned per crtc.
+         *
+         * In the worst case this is 1 + 1 + 1 + 2*2 = 7. That would fit into 3
+         * bits with absolutely no headroom. So use 4 bits. */
+        int pin_count : 4;
+#define DRM_I915_GEM_OBJECT_MAX_PIN_COUNT 0xf
 
         /** AGP memory structure for our GTT binding. */
         DRM_AGP_MEM *agp_mem;
 
         struct page **pages;
-        int pages_refcount;
 
         /**
          * Current offset of the object in GTT space.
@@ -687,21 +732,10 @@ struct drm_i915_gem_object {
          */
         uint64_t mmap_offset;
 
-        /**
-         * Fence register bits (if any) for this object.  Will be set
-         * as needed when mapped into the GTT.
-         * Protected by dev->struct_mutex.
-         */
-        int fence_reg;
-
-        /** How many users have pinned this object in GTT space */
-        int pin_count;
-
         /** Breadcrumb of last rendering to the buffer. */
         uint32_t last_rendering_seqno;
 
-        /** Current tiling mode for the object. */
-        uint32_t tiling_mode;
+        /** Current tiling stride for the object, if it's tiled. */
         uint32_t stride;
 
         /** Record of address bit 17 of each page at last unbind. */
@@ -724,17 +758,6 @@ struct drm_i915_gem_object {
         struct drm_i915_gem_phys_object *phys_obj;
 
         /**
-         * Used for checking the object doesn't appear more than once
-         * in an execbuffer object list.
-         */
-        int in_execbuffer;
-
-        /**
-         * Advice: are the backing pages purgeable?
-         */
-        int madv;
-
-        /**
          * Number of crtcs where this object is currently the fb, but
          * will be page flipped away on the next vblank.  When it
          * reaches 0, dev_priv->pending_flip_queue will be woken up.
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index c51495f15718..bf703551343a 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2247,6 +2247,9 @@ i915_gem_object_get_pages(struct drm_gem_object *obj,
         struct inode *inode;
         struct page *page;
 
+        BUG_ON(obj_priv->pages_refcount
+                        == DRM_I915_GEM_OBJECT_MAX_PAGES_REFCOUNT);
+
         if (obj_priv->pages_refcount++ != 0)
                 return 0;
 
@@ -4156,6 +4159,8 @@ i915_gem_object_pin(struct drm_gem_object *obj, uint32_t alignment)
         struct drm_i915_gem_object *obj_priv = to_intel_bo(obj);
         int ret;
 
+        BUG_ON(obj_priv->pin_count == DRM_I915_GEM_OBJECT_MAX_PIN_COUNT);
+
         i915_verify_inactive(dev, __FILE__, __LINE__);
         if (obj_priv->gtt_space == NULL) {
                 ret = i915_gem_object_bind_to_gtt(obj, alignment);