libipa: FCQueue: Make sure FrameContext#0 is initialized

Some IPA modules, like the RkISP1 one, call FCQueue::get(0) at
IPA::start() time, before any frame context has been allocated with
FCQueue::alloc() called at queueRequest() time.

The FCQueue implementation aims to detect when a FrameContext is get()
before it is alloc()-ated, Warns about it, and initializes the
FrameContext before returning it.

In case of frame#0, a get() preceding an alloc() call is not detected
as the "frame == frameContext.frame" test returns success, as
FrameContexts are zeroed by default.

As a result, the first returned FrameContext is not initialized.

Explicitly test for frame#0 to make sure the FrameContext is initialized
if get(0) is called before alloc(0). To avoid re-initializing a frame
context, in case alloc() has been called correctly before get(),
introduce an "initialised" state variable that tracks the FrameContext
initialisation state.

Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com>
Reviewed-by: Stefan Klug <stefan.klug@ideasonboard.com>

src/ipa/libipa/fc_queue.h

@@ -25,6 +25,7 @@ struct FrameContext {
 private:
 	template<typename T> friend class FCQueue;
 	uint32_t frame;
+	bool initialised = false;
 };
 
 template<typename FrameContext>
@@ -38,9 +39,11 @@ public:
 
 	void clear()
 	{
-		for (FrameContext &ctx : contexts_)
+		for (FrameContext &ctx : contexts_) {
+			ctx.initialised = false;
 			ctx.frame = 0;
 		}
+	}
 
 	FrameContext &alloc(const uint32_t frame)
 	{
@@ -83,6 +86,21 @@ public:
 					    << " has been overwritten by "
 					    << frameContext.frame;
 
+		if (frame == 0 && !frameContext.initialised) {
+			/*
+			 * If the IPA calls get() at start() time it will get an
+			 * un-intialized FrameContext as the below "frame ==
+			 * frameContext.frame" check will return success because
+			 * FrameContexts are zeroed at creation time.
+			 *
+			 * Make sure the FrameContext gets initialised if get()
+			 * is called before alloc() by the IPA for frame#0.
+			 */
+			init(frameContext, frame);
+
+			return frameContext;
+		}
+
 		if (frame == frameContext.frame)
 			return frameContext;
 
@@ -108,6 +126,7 @@ private:
 	{
 		frameContext = {};
 		frameContext.frame = frame;
+		frameContext.initialised = true;
 	}
 
 	std::vector<FrameContext> contexts_;