Pre-allocate command buffer in atomic_commit using intel_dsb_prepare
function which also includes pinning and map in cpu domain.

No change is dsb write/commit functions.

Now dsb get/put function is refactored and currently used only for
reference counting. Below dsb api added to do respective job
mentioned below.

intel_dsb_prepare - Allocate, pin and map the buffer.
intel_dsb_cleanup - Unpin and release the gem object.

RFC: Initial patch for design review.
v2: included _init() part in _prepare(). [Daniel, Ville]
v3: dsb_cleanup called after cleanup_planes. [Daniel]

Cc: Ville Syrjälä <ville.syrj...@linux.intel.com>
Cc: Jani Nikula <jani.nik...@intel.com>
Cc: Daniel Vetter <daniel.vet...@ffwll.ch>
Signed-off-by: Animesh Manna <animesh.ma...@intel.com>
---
 drivers/gpu/drm/i915/display/intel_display.c |  36 ++++-
 drivers/gpu/drm/i915/display/intel_dsb.c     | 132 ++++++++++++-------
 drivers/gpu/drm/i915/display/intel_dsb.h     |   2 +
 3 files changed, 116 insertions(+), 54 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display.c 
b/drivers/gpu/drm/i915/display/intel_display.c
index 61ba1f2256a0..ae90687e3a6b 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -15076,6 +15076,19 @@ static int intel_atomic_check(struct drm_device *dev,
 
 static int intel_atomic_prepare_commit(struct intel_atomic_state *state)
 {
+       struct intel_crtc_state *crtc_state;
+       struct intel_crtc *crtc;
+       int i;
+
+       for_each_new_intel_crtc_in_state(state, crtc, crtc_state, i) {
+               bool mode_changed = needs_modeset(crtc_state);
+
+               if (mode_changed || crtc_state->update_pipe ||
+                   crtc_state->uapi.color_mgmt_changed) {
+                       intel_dsb_prepare(crtc);
+               }
+       }
+
        return drm_atomic_helper_prepare_planes(state->base.dev,
                                                &state->base);
 }
@@ -15643,15 +15656,26 @@ static void intel_atomic_commit_fence_wait(struct 
intel_atomic_state *intel_stat
                    &wait_reset);
 }
 
+static void intel_cleanup_dsbs(struct intel_atomic_state *state)
+{
+       struct intel_crtc_state *crtc_state;
+       struct intel_crtc *crtc;
+       int i;
+
+       for_each_new_intel_crtc_in_state(state, crtc, crtc_state, i)
+               intel_dsb_cleanup(crtc);
+}
+
 static void intel_atomic_cleanup_work(struct work_struct *work)
 {
-       struct drm_atomic_state *state =
-               container_of(work, struct drm_atomic_state, commit_work);
-       struct drm_i915_private *i915 = to_i915(state->dev);
+       struct intel_atomic_state *state =
+               container_of(work, struct intel_atomic_state, base.commit_work);
+       struct drm_i915_private *i915 = to_i915(state->base.dev);
 
-       drm_atomic_helper_cleanup_planes(&i915->drm, state);
-       drm_atomic_helper_commit_cleanup_done(state);
-       drm_atomic_state_put(state);
+       drm_atomic_helper_cleanup_planes(&i915->drm, &state->base);
+       intel_cleanup_dsbs(state);
+       drm_atomic_helper_commit_cleanup_done(&state->base);
+       drm_atomic_state_put(&state->base);
 
        intel_atomic_helper_free_state(i915);
 }
diff --git a/drivers/gpu/drm/i915/display/intel_dsb.c 
b/drivers/gpu/drm/i915/display/intel_dsb.c
index 76ae01277fd6..c31132c41e0f 100644
--- a/drivers/gpu/drm/i915/display/intel_dsb.c
+++ b/drivers/gpu/drm/i915/display/intel_dsb.c
@@ -34,6 +34,86 @@
 #define DSB_BYTE_EN_SHIFT              20
 #define DSB_REG_VALUE_MASK             0xfffff
 
+/**
+ * intel_dsb_prepare() - Allocate, pin and map the DSB command buffer.
+ * @crtc: intel_crtc structure to get pipe info.
+ *
+ * This function prepare the command buffer which is used to store dsb
+ * instructions with data.
+ */
+
+void intel_dsb_prepare(struct intel_crtc *crtc)
+{
+       struct drm_device *dev = crtc->base.dev;
+       struct drm_i915_private *i915 = to_i915(dev);
+       struct intel_dsb *dsb = &crtc->dsb;
+       struct drm_i915_gem_object *obj;
+       struct i915_vma *vma;
+       u32 *buf;
+       intel_wakeref_t wakeref;
+
+       if (!HAS_DSB(i915) || dsb->cmd_buf)
+               return;
+
+       wakeref = intel_runtime_pm_get(&i915->runtime_pm);
+
+       obj = i915_gem_object_create_internal(i915, DSB_BUF_SIZE);
+       if (IS_ERR(obj)) {
+               DRM_ERROR("Gem object creation failed\n");
+               goto out;
+       }
+
+       vma = i915_gem_object_ggtt_pin(obj, NULL, 0, 0, 0);
+       if (IS_ERR(vma)) {
+               DRM_ERROR("Vma creation failed\n");
+               i915_gem_object_put(obj);
+               goto out;
+       }
+
+       buf = i915_gem_object_pin_map(vma->obj, I915_MAP_WC);
+       if (IS_ERR(buf)) {
+               DRM_ERROR("Command buffer creation failed\n");
+               goto out;
+       }
+
+       dsb->id = DSB1;
+       dsb->vma = vma;
+       dsb->cmd_buf = buf;
+
+out:
+       /*
+        * On error dsb->cmd_buf will continue to be NULL, making the writes
+        * pass-through. Leave the dangling ref to be removed later by the
+        * corresponding intel_dsb_put(): the important error message will
+        * already be logged above.
+        */
+
+       intel_runtime_pm_put(&i915->runtime_pm, wakeref);
+}
+
+/**
+ * intel_dsb_cleanup() - To cleanup DSB context.
+ * @dsb: intel_dsb structure.
+ *
+ * This function cleanup the DSB context by unpinning and releasing
+ * the VMA object associated with it.
+ */
+
+void intel_dsb_cleanup(struct intel_crtc *crtc)
+{
+       struct drm_i915_private *i915 = to_i915(crtc->base.dev);
+       struct intel_dsb *dsb = &crtc->dsb;
+
+       if (!HAS_DSB(i915))
+               return;
+
+       if (dsb->vma) {
+               i915_vma_unpin_and_release(&dsb->vma, I915_VMA_RELEASE_MAP);
+               dsb->vma = NULL;
+               dsb->cmd_buf = NULL;
+       }
+}
+
 static inline bool is_dsb_busy(struct intel_dsb *dsb)
 {
        struct intel_crtc *crtc = container_of(dsb, typeof(*crtc), dsb);
@@ -84,14 +164,13 @@ static inline bool intel_dsb_disable_engine(struct 
intel_dsb *dsb)
 }
 
 /**
- * intel_dsb_get() - Allocate DSB context and return a DSB instance.
+ * intel_dsb_get() - Return a DSB instance and increase reference count.
  * @crtc: intel_crtc structure to get pipe info.
  *
  * This function provides handle of a DSB instance, for the further DSB
  * operations.
  *
  * Returns: address of Intel_dsb instance requested for.
- * Failure: Returns the same DSB instance, but without a command buffer.
  */
 
 struct intel_dsb *
@@ -100,52 +179,11 @@ intel_dsb_get(struct intel_crtc *crtc)
        struct drm_device *dev = crtc->base.dev;
        struct drm_i915_private *i915 = to_i915(dev);
        struct intel_dsb *dsb = &crtc->dsb;
-       struct drm_i915_gem_object *obj;
-       struct i915_vma *vma;
-       u32 *buf;
-       intel_wakeref_t wakeref;
 
        if (!HAS_DSB(i915))
                return dsb;
 
-       if (dsb->refcount++ != 0)
-               return dsb;
-
-       wakeref = intel_runtime_pm_get(&i915->runtime_pm);
-
-       obj = i915_gem_object_create_internal(i915, DSB_BUF_SIZE);
-       if (IS_ERR(obj)) {
-               DRM_ERROR("Gem object creation failed\n");
-               goto out;
-       }
-
-       vma = i915_gem_object_ggtt_pin(obj, NULL, 0, 0, 0);
-       if (IS_ERR(vma)) {
-               DRM_ERROR("Vma creation failed\n");
-               i915_gem_object_put(obj);
-               goto out;
-       }
-
-       buf = i915_gem_object_pin_map(vma->obj, I915_MAP_WC);
-       if (IS_ERR(buf)) {
-               DRM_ERROR("Command buffer creation failed\n");
-               goto out;
-       }
-
-       dsb->id = DSB1;
-       dsb->vma = vma;
-       dsb->cmd_buf = buf;
-
-out:
-       /*
-        * On error dsb->cmd_buf will continue to be NULL, making the writes
-        * pass-through. Leave the dangling ref to be removed later by the
-        * corresponding intel_dsb_put(): the important error message will
-        * already be logged above.
-        */
-
-       intel_runtime_pm_put(&i915->runtime_pm, wakeref);
-
+       dsb->refcount++;
        return dsb;
 }
 
@@ -153,8 +191,8 @@ intel_dsb_get(struct intel_crtc *crtc)
  * intel_dsb_put() - To destroy DSB context.
  * @dsb: intel_dsb structure.
  *
- * This function destroys the DSB context allocated by a dsb_get(), by
- * unpinning and releasing the VMA object associated with it.
+ * This function decrease the reference count and reset the command
+ * buffer position.
  */
 
 void intel_dsb_put(struct intel_dsb *dsb)
@@ -169,8 +207,6 @@ void intel_dsb_put(struct intel_dsb *dsb)
                return;
 
        if (--dsb->refcount == 0) {
-               i915_vma_unpin_and_release(&dsb->vma, I915_VMA_RELEASE_MAP);
-               dsb->cmd_buf = NULL;
                dsb->free_pos = 0;
                dsb->ins_start_offset = 0;
        }
diff --git a/drivers/gpu/drm/i915/display/intel_dsb.h 
b/drivers/gpu/drm/i915/display/intel_dsb.h
index 395ef9ce558e..1dcce198899a 100644
--- a/drivers/gpu/drm/i915/display/intel_dsb.h
+++ b/drivers/gpu/drm/i915/display/intel_dsb.h
@@ -41,6 +41,8 @@ struct intel_dsb {
        u32 ins_start_offset;
 };
 
+void intel_dsb_prepare(struct intel_crtc *crtc);
+void intel_dsb_cleanup(struct intel_crtc *crtc);
 struct intel_dsb *
 intel_dsb_get(struct intel_crtc *crtc);
 void intel_dsb_put(struct intel_dsb *dsb);
-- 
2.24.0

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