commit f2c060f8be1ed1270728b43a2588d3b9eb00c292
author Roman Stratiienko <r.stratiienko@gmail.com> Mon Sep 18 22:46:08 2023 +0300
committer Roman Stratiienko <r.stratiienko@gmail.com> Sun Oct 01 15:00:59 2023 +0300
tree fa79d38263dbfa983067bc2bded41265ea98ac6a
parent 63762a9d5d131bb20b29d9ab92c2ddbd7dc1889e

drm_hwcomposer: Virtual display acceleration support

Some platforms like RaspberryPI-4 can benefit from Display Blender IP Core's
ability to write back the composition into RAM, offloading the GPU in cases
where the display content needs to be used (screen record, remote display,
etc.).

To enable this feature the following system property must be enabled:

    PRODUCT_VENDOR_PROPERTIES += debug.sf.enable_hwc_vds=1

The feature was requested by the Tesla Android project to improve UI
performance.

Closes: https://gitlab.freedesktop.org/drm-hwcomposer/drm-hwcomposer/-/issues/4
Change-Id: I643f94551408bf218a0b889f1a031598646242f1
Signed-off-by: Roman Stratiienko <r.stratiienko@gmail.com>

hwc2_device/HwcDisplay.cpp

diff --git a/hwc2_device/HwcDisplay.cpp b/hwc2_device/HwcDisplay.cpp
index 4ef98c3..c9d9a68 100644
--- a/hwc2_device/HwcDisplay.cpp
+++ b/hwc2_device/HwcDisplay.cpp
@@ -67,7 +67,11 @@
 
 HwcDisplay::HwcDisplay(hwc2_display_t handle, HWC2::DisplayType type,
                        DrmHwcTwo *hwc2)
-    : hwc2_(hwc2), handle_(handle), type_(type), client_layer_(this){};
+    : hwc2_(hwc2), handle_(handle), type_(type), client_layer_(this) {
+  if (type_ == HWC2::DisplayType::Virtual) {
+    writeback_layer_ = std::make_unique<HwcLayer>(this);
+  }
+}
 
 void HwcDisplay::SetColorMarixToIdentity() {
   color_matrix_ = std::make_shared<drm_color_ctm>();
@@ -160,10 +164,12 @@
       },
   };
 
-  vsync_worker_ = VSyncWorker::CreateInstance(pipeline_, vsw_callbacks);
-  if (!vsync_worker_) {
-    ALOGE("Failed to create event worker for d=%d\n", int(handle_));
-    return HWC2::Error::BadDisplay;
+  if (type_ != HWC2::DisplayType::Virtual) {
+    vsync_worker_ = VSyncWorker::CreateInstance(pipeline_, vsw_callbacks);
+    if (!vsync_worker_) {
+      ALOGE("Failed to create event worker for d=%d\n", int(handle_));
+      return HWC2::Error::BadDisplay;
+    }
   }
 
   if (!IsInHeadlessMode()) {
@@ -190,10 +196,12 @@
 
 HWC2::Error HwcDisplay::ChosePreferredConfig() {
   HWC2::Error err{};
-  if (!IsInHeadlessMode()) {
+  if (type_ == HWC2::DisplayType::Virtual) {
+    configs_.GenFakeMode(virtual_disp_width_, virtual_disp_height_);
+  } else if (!IsInHeadlessMode()) {
     err = configs_.Update(*pipeline_->connector->Get());
   } else {
-    configs_.FillHeadless();
+    configs_.GenFakeMode(0, 0);
   }
   if (!IsInHeadlessMode() && err != HWC2::Error::None) {
     return HWC2::Error::BadDisplay;
@@ -528,6 +536,13 @@
    */
   current_plan_ = DrmKmsPlan::CreateDrmKmsPlan(GetPipe(),
                                                std::move(composition_layers));
+
+  if (type_ == HWC2::DisplayType::Virtual) {
+    a_args.writeback_fb = writeback_layer_->GetLayerData().fb;
+    a_args.writeback_release_fence = writeback_layer_->GetLayerData()
+                                         .acquire_fence;
+  }
+
   if (!current_plan_) {
     if (!a_args.test_only) {
       ALOGE("Failed to create DrmKmsPlan");
@@ -722,10 +737,16 @@
   return true;
 }
 
-HWC2::Error HwcDisplay::SetOutputBuffer(buffer_handle_t /*buffer*/,
-                                        int32_t /*release_fence*/) {
-  // TODO(nobody): Need virtual display support
-  return HWC2::Error::Unsupported;
+HWC2::Error HwcDisplay::SetOutputBuffer(buffer_handle_t buffer,
+                                        int32_t release_fence) {
+  writeback_layer_->SetLayerBuffer(buffer, release_fence);
+  writeback_layer_->PopulateLayerData();
+  if (!writeback_layer_->IsLayerUsableAsDevice()) {
+    ALOGE("Output layer must be always usable by DRM/KMS");
+    return HWC2::Error::BadLayer;
+  }
+  /* TODO: Check if format is supported by writeback connector */
+  return HWC2::Error::None;
 }
 
 HWC2::Error HwcDisplay::SetPowerMode(int32_t mode_in) {
@@ -773,6 +794,10 @@
 }
 
 HWC2::Error HwcDisplay::SetVsyncEnabled(int32_t enabled) {
+  if (type_ == HWC2::DisplayType::Virtual) {
+    return HWC2::Error::None;
+  }
+
   vsync_event_en_ = HWC2_VSYNC_ENABLE == enabled;
   if (vsync_event_en_) {
     vsync_worker_->VSyncControl(true);
@@ -845,6 +870,10 @@
     hwc2_config_t config,
     hwc_vsync_period_change_constraints_t *vsyncPeriodChangeConstraints,
     hwc_vsync_period_change_timeline_t *outTimeline) {
+  if (type_ == HWC2::DisplayType::Virtual) {
+    return HWC2::Error::None;
+  }
+
   if (vsyncPeriodChangeConstraints == nullptr || outTimeline == nullptr) {
     return HWC2::Error::BadParameter;
   }