[PATCH v5 08/11] drm/i915/dsb: added dsb refcount to synchronize between get/put.

[Animesh Manna <animesh.manna@xxxxxxxxx>]

The lifetime of command buffer can be controlled by the dsb user
throuh refcount. Added refcount mechanism is dsb get/put call
which create/destroy dsb context.

Cc: Jani Nikula <jani.nikula@xxxxxxxxx>
Cc: Shashank Sharma <shashank.sharma@xxxxxxxxx>
Signed-off-by: Animesh Manna <animesh.manna@xxxxxxxxx>
---
 drivers/gpu/drm/i915/display/intel_dsb.c | 22 ++++++++++++++++------
 drivers/gpu/drm/i915/display/intel_dsb.h |  1 +
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dsb.c b/drivers/gpu/drm/i915/display/intel_dsb.c
index 853685751540..b951a6b5264a 100644
--- a/drivers/gpu/drm/i915/display/intel_dsb.c
+++ b/drivers/gpu/drm/i915/display/intel_dsb.c
@@ -78,7 +78,12 @@ intel_dsb_get(struct intel_crtc *crtc)
 	struct intel_dsb *dsb = &crtc->dsb;
 	intel_wakeref_t wakeref;
 
-	if ((!HAS_DSB(i915)) || dsb->cmd_buf)
+	if (!HAS_DSB(i915))
+		return dsb;
+
+	atomic_inc(&dsb->refcount);
+
+	if (dsb->cmd_buf)
 		return dsb;
 
 	dsb->id = DSB1;
@@ -94,6 +99,7 @@ intel_dsb_get(struct intel_crtc *crtc)
 	if (IS_ERR(vma)) {
 		DRM_ERROR("Vma creation failed.\n");
 		i915_gem_object_put(obj);
+		atomic_dec(&dsb->refcount);
 		goto err;
 	}
 
@@ -102,6 +108,7 @@ intel_dsb_get(struct intel_crtc *crtc)
 		DRM_ERROR("Command buffer creation failed.\n");
 		i915_vma_unpin_and_release(&vma, 0);
 		dsb->cmd_buf = NULL;
+		atomic_dec(&dsb->refcount);
 		goto err;
 	}
 	dsb->vma = vma;
@@ -121,11 +128,14 @@ void intel_dsb_put(struct intel_dsb *dsb)
 		return;
 
 	if (dsb->cmd_buf) {
-		mutex_lock(&i915->drm.struct_mutex);
-		i915_gem_object_unpin_map(dsb->vma->obj);
-		i915_vma_unpin_and_release(&dsb->vma, 0);
-		dsb->cmd_buf = NULL;
-		mutex_unlock(&i915->drm.struct_mutex);
+		atomic_dec(&dsb->refcount);
+		if (!atomic_read(&dsb->refcount)) {
+			mutex_lock(&i915->drm.struct_mutex);
+			i915_gem_object_unpin_map(dsb->vma->obj);
+			i915_vma_unpin_and_release(&dsb->vma, 0);
+			dsb->cmd_buf = NULL;
+			mutex_unlock(&i915->drm.struct_mutex);
+		}
 	}
 }
 
diff --git a/drivers/gpu/drm/i915/display/intel_dsb.h b/drivers/gpu/drm/i915/display/intel_dsb.h
index 7389c8c5b665..dca4e632dd3c 100644
--- a/drivers/gpu/drm/i915/display/intel_dsb.h
+++ b/drivers/gpu/drm/i915/display/intel_dsb.h
@@ -20,6 +20,7 @@ enum dsb_id {
 };
 
 struct intel_dsb {
+	atomic_t refcount;
 	enum dsb_id id;
 	u32 *cmd_buf;
 	struct i915_vma *vma;
-- 
2.22.0

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