[libcamera-devel] [PATCH 7/8] cam: kms_sink: Enable display on first frame

[Laurent Pinchart]

Not all display controllers support enabling the display without any
active plane. Delay display enabling to the first frame.

Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
---
 src/cam/kms_sink.cpp | 31 +++++++++++--------------------
 src/cam/kms_sink.h   |  2 --
 2 files changed, 11 insertions(+), 22 deletions(-)

diff --git a/src/cam/kms_sink.cpp b/src/cam/kms_sink.cpp
index 85f244ea5413..a769255c022e 100644
--- a/src/cam/kms_sink.cpp
+++ b/src/cam/kms_sink.cpp
@@ -184,23 +184,6 @@ int KMSSink::start()
 		return ret;
 	}
 
-	/* Enable the display pipeline with no plane to start with. */
-	request = std::make_unique<DRM::AtomicRequest>(&dev_);
-
-	request->addProperty(connector_, "CRTC_ID", crtc_->id());
-	request->addProperty(crtc_, "ACTIVE", 1);
-	request->addProperty(crtc_, "MODE_ID", mode_->toBlob(&dev_));
-
-	ret = request->commit(DRM::AtomicRequest::FlagAllowModeset);
-	if (ret < 0) {
-		std::cerr
-			<< "Failed to enable display pipeline: "
-			<< strerror(-ret) << std::endl;
-		return ret;
-	}
-
-	planeInitialized_ = false;
-
 	return 0;
 }
 
@@ -244,10 +227,17 @@ bool KMSSink::consumeBuffer(const libcamera::Stream *stream,
 
 	DRM::FrameBuffer *drmBuffer = iter->second.get();
 
+	unsigned int flags = DRM::AtomicRequest::FlagAsync;
 	DRM::AtomicRequest *request = new DRM::AtomicRequest(&dev_);
 	request->addProperty(plane_, "FB_ID", drmBuffer->id());
 
-	if (!planeInitialized_) {
+	if (!active_ && !queued_) {
+		/* Enable the display pipeline on the first frame. */
+		request->addProperty(connector_, "CRTC_ID", crtc_->id());
+
+		request->addProperty(crtc_, "ACTIVE", 1);
+		request->addProperty(crtc_, "MODE_ID", mode_->toBlob(&dev_));
+
 		request->addProperty(plane_, "CRTC_ID", crtc_->id());
 		request->addProperty(plane_, "SRC_X", 0 << 16);
 		request->addProperty(plane_, "SRC_Y", 0 << 16);
@@ -257,7 +247,8 @@ bool KMSSink::consumeBuffer(const libcamera::Stream *stream,
 		request->addProperty(plane_, "CRTC_Y", 0);
 		request->addProperty(plane_, "CRTC_W", mode_->hdisplay);
 		request->addProperty(plane_, "CRTC_H", mode_->vdisplay);
-		planeInitialized_ = true;
+
+		flags |= DRM::AtomicRequest::FlagAllowModeset;
 	}
 
 	pending_ = std::make_unique<Request>(request, buffer);
@@ -265,7 +256,7 @@ bool KMSSink::consumeBuffer(const libcamera::Stream *stream,
 	std::lock_guard<std::mutex> lock(lock_);
 
 	if (!queued_) {
-		int ret = request->commit(DRM::AtomicRequest::FlagAsync);
+		int ret = request->commit(flags);
 		if (ret < 0)
 			std::cerr
 				<< "Failed to commit atomic request: "
diff --git a/src/cam/kms_sink.h b/src/cam/kms_sink.h
index ee257a071c24..0879bb559e5a 100644
--- a/src/cam/kms_sink.h
+++ b/src/cam/kms_sink.h
@@ -63,8 +63,6 @@ private:
 	libcamera::Size size_;
 	unsigned int stride_;
 
-	bool planeInitialized_;
-
 	std::map<libcamera::FrameBuffer *, std::unique_ptr<DRM::FrameBuffer>> buffers_;
 
 	std::mutex lock_;
-- 
Regards,

Laurent Pinchart