intel/display: make effective use of PSR

- only mark framebuffer dirty if necessary
  -> gives the hardware chance to save longer power
- remove extra timer connection on Genode component side
  -> use Linux time primitives

Issue #5339

repos/pc/src/driver/framebuffer/intel/pc/lx_i915.h

@@ -32,6 +32,7 @@ struct genode_mode {
 	char name[32];
 };
 
+int  lx_emul_i915_blit(void);
 void lx_emul_i915_report(void * genode_xml);
 void lx_emul_i915_hotplug_connector(void);
 void lx_emul_i915_report_connector(void * lx_data, void * genode_xml,

repos/pc/src/driver/framebuffer/intel/pc/lx_user.c

@@ -504,8 +504,12 @@ void framebuffer_dirty(void)
 static int update_content(void *)
 {
 	while (true) {
-		framebuffer_dirty();
+
-		lx_emul_task_schedule(true /* block task */);
+		if (lx_emul_i915_blit())
+			framebuffer_dirty();
+
+		/* schedule_timeout(jiffes) or hrtimer or msleep */
+		msleep(20);
 	}
 
 	return 0;

repos/pc/src/driver/framebuffer/intel/pc/main.cc

@@ -13,7 +13,6 @@
 
 #include <base/attached_rom_dataspace.h>
 #include <base/component.h>
-#include <timer_session/connection.h>
 #include <capture_session/connection.h>
 #include <os/pixel_rgb888.h>
 #include <os/reporter.h>
@@ -33,7 +32,6 @@ extern "C" {
 
 
 extern struct task_struct * lx_user_task;
-extern struct task_struct * lx_update_task;
 
 
 namespace Framebuffer {
@@ -47,15 +45,12 @@ struct Framebuffer::Driver
 	using Attached_rom_system = Constructible<Attached_rom_dataspace>;
 
 	Env                    &env;
-	Timer::Connection       timer    { env };
 	Attached_rom_dataspace  config   { env, "config" };
 	Attached_rom_system     system   { };
 	Expanding_reporter      reporter { env, "connectors", "connectors" };
 
 	Signal_handler<Driver>  config_handler    { env.ep(), *this,
 	                                            &Driver::config_update };
-	Signal_handler<Driver>  timer_handler     { env.ep(), *this,
-	                                            &Driver::handle_timer };
 	Signal_handler<Driver>  scheduler_handler { env.ep(), *this,
 	                                            &Driver::handle_scheduler };
 	Signal_handler<Driver>  system_handler    { env.ep(), *this,
@@ -84,17 +79,29 @@ struct Framebuffer::Driver
 
 		public:
 
-			void paint()
+			bool paint()
 			{
 				using Pixel = Capture::Pixel;
-				Surface<Pixel> surface((Pixel*)_base, _size_phys);
-				_captured_screen.apply_to_surface(surface);
 
-				if (!lx_update_task)
+				bool dirty = false;
-					return;
 
-				lx_emul_task_unblock(lx_update_task);
+				_captured_screen.with_texture([&] (Texture<Pixel> const &texture) {
-				Lx_kit::env().scheduler.execute();
+
+					auto const affected = _capture.capture_at(Capture::Point(0, 0));
+
+					affected.for_each_rect([&] (Capture::Rect const rect) {
+
+						Surface<Pixel> surface((Pixel*)_base, _size_phys);
+
+						surface.clip(rect);
+
+						Blit_painter::paint(surface, texture, Capture::Point(0, 0));
+
+						dirty = true;
+					});
+				});
+
+				return dirty;
 			}
 
 			Fb(Env & env, void * base, Capture::Area size,
@@ -121,11 +128,6 @@ struct Framebuffer::Driver
 	void generate_report();
 	void lookup_config(char const *, struct genode_mode &mode);
 
-	void handle_timer()
-	{
-		if (fb.constructed()) { fb->paint(); }
-	}
-
 	void handle_scheduler()
 	{
 		Lx_kit::env().scheduler.execute();
@@ -164,9 +166,6 @@ struct Framebuffer::Driver
 		log("--- Intel framebuffer driver started ---");
 
 		lx_emul_start_kernel(nullptr);
-
-		timer.sigh(timer_handler);
-		timer.trigger_periodic(20*1000);
 	}
 
 	bool apply_config_on_hotplug() const
@@ -467,6 +466,17 @@ void lx_emul_i915_report_modes(void * genode_xml, struct genode_mode *mode)
 }
 
 
+int lx_emul_i915_blit()
+{
+	auto &drv = driver(Lx_kit::env().env);
+
+	if (!drv.fb.constructed())
+		return false;
+
+	return drv.fb->paint();
+}
+
+
 void lx_emul_i915_connector_config(char * name, struct genode_mode * mode)
 {
 	if (!mode || !name)