SF: Flow DisplayModeRequest through mode set FSM

The motivation is to:
    - Avoid redundant state that can cause data races if stale.
    - Consolidate control flow for resolution and refresh rate changes.
    - Clarify the desired/pending/active states of the per-display FSM.

The notable changes are:

Consume the desired DisplayModeRequestOpt via either SF::dropModeRequest
or DisplayDevice::initiateModeChange.

Pull the details of SF::finalizeDisplayModeChange into DisplayDevice::
finalizeModeChange, which now returns whether there was NoModeChange,
a ResolutionChange, or a RefreshRateChange. Consume the pending request.

Now that DisplayDevice does not retain the desired DisplayModeRequest,
applyActiveMode as soon as finalizeDisplayModeChange ends, rather than
at a later point in the commit, when initiateDisplayModeChanges checks
whether the active and desired modes are the same.

Now that applyActiveMode happens in finalizeDisplayModeChange, remove
the special case when there is a displayToUpdateImmediately.

Bug: 305813445
Bug: 255635711
Bug: 241285876
Test: ALOGV of mode setting for inner/outer displays
Test: InitiateModeChangeTest, DisplayModeSwitchingTest
Change-Id: I688b0c922747a80e881965a1dc243d11ba2c7438

1 files changed, 24 insertions, 8 deletions

diff --git a/services/surfaceflinger/DisplayDevice.cpp b/services/surfaceflinger/DisplayDevice.cpp
index 950b05e1da..671382c98e 100644
--- a/services/surfaceflinger/DisplayDevice.cpp
+++ b/services/surfaceflinger/DisplayDevice.cpp
@@ -222,7 +222,6 @@ bool DisplayDevice::initiateModeChange(display::DisplayModeRequest&& desiredMode
                                        const hal::VsyncPeriodChangeConstraints& constraints,
                                        hal::VsyncPeriodChangeTimeline& outTimeline) {
     mPendingModeOpt = std::move(desiredMode);
-    mIsModeSetPending = true;
 
     const auto& mode = *mPendingModeOpt->mode.modePtr;
 
@@ -235,9 +234,22 @@ bool DisplayDevice::initiateModeChange(display::DisplayModeRequest&& desiredMode
     return true;
 }
 
-void DisplayDevice::finalizeModeChange(DisplayModeId modeId, Fps vsyncRate, Fps renderFps) {
-    setActiveMode(modeId, vsyncRate, renderFps);
-    mIsModeSetPending = false;
+auto DisplayDevice::finalizeModeChange() -> ModeChange {
+    if (!mPendingModeOpt) return NoModeChange{"No pending mode"};
+
+    auto pendingMode = *std::exchange(mPendingModeOpt, std::nullopt);
+    auto& pendingModePtr = pendingMode.mode.modePtr;
+
+    if (!mRefreshRateSelector->displayModes().contains(pendingModePtr->getId())) {
+        return NoModeChange{"Unknown pending mode"};
+    }
+
+    if (getActiveMode().modePtr->getResolution() != pendingModePtr->getResolution()) {
+        return ResolutionChange{std::move(pendingMode)};
+    }
+
+    setActiveMode(pendingModePtr->getId(), pendingModePtr->getVsyncRate(), pendingMode.mode.fps);
+    return RefreshRateChange{std::move(pendingMode)};
 }
 
 nsecs_t DisplayDevice::getVsyncPeriodFromHWC() const {
@@ -571,10 +583,14 @@ auto DisplayDevice::getDesiredMode() const -> DisplayModeRequestOpt {
     return mDesiredModeOpt;
 }
 
-void DisplayDevice::clearDesiredMode() {
-    std::scoped_lock lock(mDesiredModeLock);
-    mDesiredModeOpt.reset();
-    mHasDesiredModeTrace = false;
+auto DisplayDevice::takeDesiredMode() -> DisplayModeRequestOpt {
+    DisplayModeRequestOpt desiredModeOpt;
+    {
+        std::scoped_lock lock(mDesiredModeLock);
+        std::swap(mDesiredModeOpt, desiredModeOpt);
+        mHasDesiredModeTrace = false;
+    }
+    return desiredModeOpt;
 }
 
 void DisplayDevice::adjustRefreshRate(Fps pacesetterDisplayRefreshRate) {