[PATCH 07/16] drm/i915: Mark up obj->pin_global as being atomic

[Chris Wilson]

Coming up next, we will want to manipulate the pin_global counter
outside of the principle locks, so convert it to an atomic.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/gem/i915_gem_domain.c       | 12 ++++++------
 drivers/gpu/drm/i915/gem/i915_gem_object.h       |  3 ++-
 drivers/gpu/drm/i915/gem/i915_gem_object_types.h |  2 +-
 drivers/gpu/drm/i915/gem/i915_gem_shrinker.c     |  2 +-
 drivers/gpu/drm/i915/i915_debugfs.c              |  4 ++--
 5 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_domain.c b/drivers/gpu/drm/i915/gem/i915_gem_domain.c
index fbe51f4852ab..2b5d6e9202fe 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_domain.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_domain.c
@@ -27,7 +27,7 @@ static void __i915_gem_object_flush_for_display(struct drm_i915_gem_object *obj)
 
 void i915_gem_object_flush_if_display(struct drm_i915_gem_object *obj)
 {
-	if (!READ_ONCE(obj->pin_global))
+	if (!atomic_read(&obj->pin_global))
 		return;
 
 	i915_gem_object_lock(obj);
@@ -414,7 +414,7 @@ i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj,
 	/* Mark the global pin early so that we account for the
 	 * display coherency whilst setting up the cache domains.
 	 */
-	obj->pin_global++;
+	atomic_inc(&obj->pin_global);
 
 	/* The display engine is not coherent with the LLC cache on gen6.  As
 	 * a result, we make sure that the pinning that is about to occur is
@@ -464,7 +464,7 @@ i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj,
 	return vma;
 
 err_unpin_global:
-	obj->pin_global--;
+	atomic_dec(&obj->pin_global);
 	return vma;
 }
 
@@ -504,11 +504,11 @@ i915_gem_object_unpin_from_display_plane(struct i915_vma *vma)
 
 	assert_object_held(obj);
 
-	if (WARN_ON(obj->pin_global == 0))
+	if (GEM_WARN_ON(!atomic_read(&obj->pin_global)))
 		return;
 
-	if (--obj->pin_global == 0)
-		vma->display_alignment = I915_GTT_MIN_ALIGNMENT;
+	if (atomic_dec_and_test(&obj->pin_global))
+		vma->display_alignment = I915_GTT_MIN_ALIGNMENT; /* XXX race */
 
 	/* Bump the LRU to try and avoid premature eviction whilst flipping  */
 	i915_gem_object_bump_inactive_ggtt(obj);
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h b/drivers/gpu/drm/i915/gem/i915_gem_object.h
index 5efb9936e05b..11bb1a412e4f 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h
@@ -406,7 +406,8 @@ static inline bool cpu_write_needs_clflush(struct drm_i915_gem_object *obj)
 	if (!(obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_WRITE))
 		return true;
 
-	return obj->pin_global; /* currently in use by HW, keep flushed */
+	/* Currently in use by HW (display engine)? Keep flushed. */
+	return atomic_read(&obj->pin_global);
 }
 
 static inline void __start_cpu_write(struct drm_i915_gem_object *obj)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
index 511fce7913ec..a09e74e27734 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
@@ -153,7 +153,7 @@ struct drm_i915_gem_object {
 	/** Count of VMA actually bound by this object */
 	atomic_t bind_count;
 	/** Count of how many global VMA are currently pinned for use by HW */
-	unsigned int pin_global;
+	atomic_t pin_global;
 
 	struct {
 		struct mutex lock; /* protects the pages and their use */
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c b/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c
index 94970f60d7f6..841f18386b54 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c
@@ -78,7 +78,7 @@ static bool can_release_pages(struct drm_i915_gem_object *obj)
 	 * To simplify the scan, and to avoid walking the list of vma under the
 	 * object, we just check the count of its permanently pinned.
 	 */
-	if (READ_ONCE(obj->pin_global))
+	if (atomic_read(&obj->pin_global))
 		return false;
 
 	/* We can only return physical pages to the system if we can either
diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index b0f51591f2e4..8d94f54c8959 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -79,7 +79,7 @@ static int i915_capabilities(struct seq_file *m, void *data)
 
 static char get_pin_flag(struct drm_i915_gem_object *obj)
 {
-	return obj->pin_global ? 'p' : ' ';
+	return atomic_read(&obj->pin_global) ? 'p' : ' ';
 }
 
 static char get_tiling_flag(struct drm_i915_gem_object *obj)
@@ -221,7 +221,7 @@ describe_obj(struct seq_file *m, struct drm_i915_gem_object *obj)
 	seq_printf(m, " (pinned x %d)", pin_count);
 	if (obj->stolen)
 		seq_printf(m, " (stolen: %08llx)", obj->stolen->start);
-	if (obj->pin_global)
+	if (atomic_read(&obj->pin_global))
 		seq_printf(m, " (global)");
 
 	engine = i915_gem_object_last_write_engine(obj);
-- 
2.23.0