commit 747747127f7918862e1299d76ebea352f68f14cc
author Roman Stratiienko <r.stratiienko@gmail.com> Fri Feb 05 16:32:47 2021 +0200
committer Roman Stratiienko <r.stratiienko@gmail.com> Fri Mar 19 15:35:15 2021 +0200
tree 045b6f4fb53c1978d038c06d20dd1e1937396cf3
parent 310e3b7f811b82e457fbd7eb84b3736da5d46631

drm_hwcomposer: Remove writeback-based flattening logic

Writeback Pros:
a. Very tiny reduction in power consumption required for
   rendering the composition compared to CLIENT-based flattening.

Writeback Cons:
a. A lot of extra code. High maintenance cost(effort).
   Nobody tests it as for now.
b. Writeback isn't implemented by the set of KMS drivers
c. Require separate memory buffer to be allocated

Part of: https://gitlab.freedesktop.org/drm-hwcomposer/drm-hwcomposer/-/issues/47
Signed-off-by: Roman Stratiienko <r.stratiienko@gmail.com>

compositor/DrmDisplayCompositor.h

diff --git a/compositor/DrmDisplayCompositor.h b/compositor/DrmDisplayCompositor.h
index 92dadca..8660a6d 100644
--- a/compositor/DrmDisplayCompositor.h
+++ b/compositor/DrmDisplayCompositor.h
@@ -26,16 +26,11 @@
 #include <tuple>
 
 #include "DrmDisplayComposition.h"
-#include "DrmFramebuffer.h"
 #include "Planner.h"
 #include "drm/ResourceManager.h"
 #include "drm/VSyncWorker.h"
 #include "drmhwcomposer.h"
 
-// One for the front, one for the back, and one for cases where we need to
-// squash a frame that the hw can't display with hw overlays.
-#define DRM_DISPLAY_BUFFERS 3
-
 // If a scene is still for this number of vblanks flatten it to reduce power
 // consumption.
 #define FLATTEN_COUNTDOWN_INIT 60
@@ -47,8 +42,6 @@
   kNotNeeded,
   kClientRequested,
   kClientDone,
-  kSerial,
-  kConcurrent
 };
 
 std::ostream &operator<<(std::ostream &str, FlatteningState state);
@@ -106,27 +99,17 @@
   static const int kAcquireWaitTries = 5;
   static const int kAcquireWaitTimeoutMs = 100;
 
-  int CommitFrame(DrmDisplayComposition *display_comp, bool test_only,
-                  DrmConnector *writeback_conn = NULL,
-                  DrmHwcBuffer *writeback_buffer = NULL);
-  int SetupWritebackCommit(drmModeAtomicReqPtr pset, uint32_t crtc_id,
-                           DrmConnector *writeback_conn,
-                           DrmHwcBuffer *writeback_buffer);
+  int CommitFrame(DrmDisplayComposition *display_comp, bool test_only);
   int ApplyDpms(DrmDisplayComposition *display_comp);
   int DisablePlanes(DrmDisplayComposition *display_comp);
 
   void ApplyFrame(std::unique_ptr<DrmDisplayComposition> composition,
-                  int status, bool writeback = false);
+                  int status);
 
   void SetFlattening(FlatteningState new_state);
   bool IsFlatteningNeeded() const;
   int FlattenActiveComposition();
   int FlattenOnClient();
-  int FlattenSerial(DrmConnector *writeback_conn);
-  int FlattenConcurrent(DrmConnector *writeback_conn);
-  int FlattenOnDisplay(std::unique_ptr<DrmDisplayComposition> &src,
-                       DrmConnector *writeback_conn, DrmMode &src_mode,
-                       DrmHwcLayer *writeback_layer);
 
   bool CountdownExpired() const;
 
@@ -143,9 +126,6 @@
 
   ModeState mode_;
 
-  int framebuffer_index_{};
-  DrmFramebuffer framebuffers_[DRM_DISPLAY_BUFFERS];
-
   // mutable since we need to acquire in Dump()
   mutable pthread_mutex_t lock_{};
 
@@ -156,7 +136,6 @@
   VSyncWorker vsync_worker_;
   int64_t flatten_countdown_;
   std::unique_ptr<Planner> planner_;
-  int writeback_fence_;
 
   FlatteningState flattening_state_;
   uint32_t frames_flattened_;