drm/i915: Clarify the semantics of tiling_changed

Rename obj->tiling_changed to obj->fence_dirty so that it is clear that
it flags when the parameters for an active fence (including the
no-fence) register are changed.

Also, do not set this flag when the object does not have a fence
register allocated currently and the gpu does not depend upon the
unfence. This case works exactly like when a tiled object lost its
fence and hence does not need additional handling for the tiling
change in the code.

v2: Use fence_dirty to better express what the flag tracks and add a few
more details to the comments to serve as a reminder of how the GPU also
uses the unfenced register slot.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
[danvet: Add some bikeshed to the commit message about the stricter
use of fence_dirty.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 4cbc45f..faea1b6 100644 (file)
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -869,7 +869,14 @@ struct drm_i915_gem_object {
         * Current tiling mode for the object.
         */
        unsigned int tiling_mode:2;
-       unsigned int tiling_changed:1;
+       /**
+        * Whether the tiling parameters for the currently associated fence
+        * register have changed. Note that for the purposes of tracking
+        * tiling changes we also treat the unfenced register, the register
+        * slot that the object occupies whilst it executes a fenced
+        * command (such as BLT on gen2/3), as a "fence".
+        */
+       unsigned int fence_dirty:1;
 
        /** How many users have pinned this object in GTT space. The following
         * users can each hold at most one reference: pwrite/pread, pin_ioctl

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 9e9ea75..38490cd 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -66,7 +66,7 @@ static inline void i915_gem_object_fence_lost(struct drm_i915_gem_object *obj)
        /* As we do not have an associated fence register, we will force
         * a tiling change if we ever need to acquire one.
         */
-       obj->tiling_changed = false;
+       obj->fence_dirty = false;
        obj->fence_reg = I915_FENCE_REG_NONE;
 }
 
@@ -2459,7 +2459,7 @@ i915_gem_object_get_fence(struct drm_i915_gem_object *obj)
        /* Have we updated the tiling parameters upon the object and so
         * will need to serialise the write to the associated fence register?
         */
-       if (obj->tiling_changed) {
+       if (obj->fence_dirty) {
                ret = i915_gem_object_flush_fence(obj);
                if (ret)
                        return ret;
@@ -2468,7 +2468,7 @@ i915_gem_object_get_fence(struct drm_i915_gem_object *obj)
        /* Just update our place in the LRU if our fence is getting reused. */
        if (obj->fence_reg != I915_FENCE_REG_NONE) {
                reg = &dev_priv->fence_regs[obj->fence_reg];
-               if (!obj->tiling_changed) {
+               if (!obj->fence_dirty) {
                        list_move_tail(&reg->lru_list,
                                       &dev_priv->mm.fence_list);
                        return 0;
@@ -2491,7 +2491,7 @@ i915_gem_object_get_fence(struct drm_i915_gem_object *obj)
                return 0;
 
        i915_gem_object_update_fence(obj, reg, enable);
-       obj->tiling_changed = false;
+       obj->fence_dirty = false;
 
        return 0;
 }

diff --git a/drivers/gpu/drm/i915/i915_gem_tiling.c b/drivers/gpu/drm/i915/i915_gem_tiling.c
index 1a93066..c9786cd 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_tiling.c
+++ b/drivers/gpu/drm/i915/i915_gem_tiling.c
@@ -355,6 +355,11 @@ i915_gem_set_tiling(struct drm_device *dev, void *data,
                 * no longer meets the alignment restrictions for its new
                 * tiling mode. Otherwise we can just leave it alone, but
                 * need to ensure that any fence register is cleared.
+                *
+                * After updating the tiling parameters, we then flag whether
+                * we need to update an associated fence register. Note this
+                * has to also include the unfenced register the GPU uses
+                * whilst executing a fenced command for an untiled object.
                 */
                i915_gem_release_mmap(obj);
 
@@ -374,7 +379,10 @@ i915_gem_set_tiling(struct drm_device *dev, void *data,
                }
 
                if (ret == 0) {
-                       obj->tiling_changed = true;
+                       obj->fence_dirty =
+                               obj->fenced_gpu_access ||
+                               obj->fence_reg != I915_FENCE_REG_NONE;
+
                        obj->tiling_mode = args->tiling_mode;
                        obj->stride = args->stride;
                }