fix(zaparoo): drop CRT mode rewrites

Author: asturur

support/zaparoo/alt_launcher.cpp

@@ -70,7 +70,7 @@ static int s_crash_count = 0;
 static unsigned long s_respawn_timer = 0;
 static unsigned long s_tty_deadline = 0;
 static unsigned long s_native_status_timer = 0;
-static unsigned long s_native_fb_mode_timer = 0;
+static unsigned long s_native_crt_finish_timer = 0;
 static bool s_gave_up = false;
 static bool s_init_pending = false;
 static bool s_native_crt = false;
@@ -82,6 +82,8 @@ static const char s_tty_path[] = "/dev/tty2";
 static const char s_fb_mode_path[] = "/sys/module/MiSTer_fb/parameters/mode";
 static const char s_crt_state_file[] = "zaparoo_launcher_crt.bin";
 static const char s_offsets_file[] = "zaparoo_video_offsets.bin";
+static char s_saved_fb_mode[64];
+static bool s_saved_fb_mode_valid = false;
 
 static int8_t s_h_offset = 0;
 static int8_t s_v_offset = 0;
@@ -135,6 +137,50 @@ static void set_launcher_fb_mode(int fmt, int rb, int width, int height, int str
 		printf("alt_launcher: fb mode set to %dx%d fmt=%d stride=%d\n", width, height, fmt, stride);
 }
 
+static void save_current_fb_mode(void)
+{
+	if (s_saved_fb_mode_valid)
+		return;
+
+	FILE *fp = fopen(s_fb_mode_path, "rt");
+	if (!fp)
+	{
+		printf("alt_launcher: unable to read fb mode: %s\n", strerror(errno));
+		return;
+	}
+
+	if (fgets(s_saved_fb_mode, sizeof(s_saved_fb_mode), fp))
+	{
+		size_t len = strlen(s_saved_fb_mode);
+		while (len && (s_saved_fb_mode[len - 1] == '\n' || s_saved_fb_mode[len - 1] == '\r'))
+			s_saved_fb_mode[--len] = 0;
+		s_saved_fb_mode_valid = len != 0;
+		if (s_saved_fb_mode_valid)
+			printf("alt_launcher: saved fb mode '%s'\n", s_saved_fb_mode);
+	}
+	fclose(fp);
+}
+
+static void restore_saved_fb_mode(void)
+{
+	if (!s_saved_fb_mode_valid)
+	{
+		set_launcher_fb_mode(8888, 1, 960, 720, 3840);
+		return;
+	}
+
+	FILE *fp = fopen(s_fb_mode_path, "wt");
+	if (!fp)
+	{
+		printf("alt_launcher: unable to restore fb mode: %s\n", strerror(errno));
+		return;
+	}
+
+	fprintf(fp, "%s\n", s_saved_fb_mode);
+	fclose(fp);
+	printf("alt_launcher: restored fb mode '%s'\n", s_saved_fb_mode);
+}
+
 static void set_native_crt_fb_mode(bool log = true)
 {
 	set_launcher_fb_mode(8888, 1, 320, 240, 1280, log);
@@ -228,31 +274,34 @@ static void disable_native_crt_path(void)
 	user_io_status_set("[9]", 0);
 	video_fb_enable(0);
 	set_vga_fb(0);
-	set_launcher_fb_mode(8888, 1, 960, 720, 3840);
+	restore_saved_fb_mode();
+	s_tty_deadline = 0;
 	s_native_status_timer = 0;
-	s_native_fb_mode_timer = 0;
+	s_native_crt_finish_timer = 0;
 }
 
-static void enable_native_crt_path(void)
+static void prepare_native_crt_path(void)
 {
 	set_vga_fb(0);
 	video_fb_enable(0);
-
-	// Double-write with a settle window so the kernel module's 320x240 layout
-	// is live before status[9] flips. Without this, the frontend renders for
-	// up to a second under stale dims (the post-fork retry timer used to be
-	// what eventually fixed the picture).
+	save_current_fb_mode();
 	set_native_crt_fb_mode(false);
-	usleep(100000);
-	set_native_crt_fb_mode();
+	s_native_crt_finish_timer = GetTimer(1);
+	if (!s_native_crt_finish_timer) s_native_crt_finish_timer = 1;
+}
+
+static void finish_native_crt_path(void)
+{
+	// The frontend repeats the 320x240 linuxfb `vmode` while it starts. This
+	// side does not rewrite the mode again; it only blanks the native DDR
+	// scan-out buffer before status[9] routes the FPGA to it.
+	s_native_crt_finish_timer = 0;
 
 	blank_native_crt_fb();
 
 	user_io_status_set("[9]", 1);
 	s_native_status_timer = GetTimer(500);
 	if (!s_native_status_timer) s_native_status_timer = 1;
-	s_native_fb_mode_timer = GetTimer(1000);
-	if (!s_native_fb_mode_timer) s_native_fb_mode_timer = 1;
 }
 
 static void return_to_normal_mode(void)
@@ -274,6 +323,8 @@ static void reset_launcher_state(void)
 	s_pid = 0;
 	s_respawn_timer = 0;
 	s_tty_deadline = 0;
+	s_native_status_timer = 0;
+	s_native_crt_finish_timer = 0;
 	s_crash_count = 0;
 	s_gave_up = false;
 	s_init_pending = false;
@@ -392,8 +443,8 @@ static void spawn(void)
 	printf("alt_launcher: native_crt=%d\n", s_native_crt);
 	if (s_native_crt)
 	{
-		enable_native_crt_path();
-		printf("alt_launcher: native CRT path enabled\n");
+		prepare_native_crt_path();
+		printf("alt_launcher: native CRT path prepared\n");
 	}
 	else
 	{
@@ -427,7 +478,7 @@ bool alt_launcher_active(void)
 
 bool alt_launcher_scheduler_sleep_enabled(void)
 {
-	return s_pid || s_init_pending || s_respawn_timer || s_tty_deadline;
+	return s_pid || s_init_pending || s_respawn_timer || s_tty_deadline || s_native_crt_finish_timer;
 }
 
 bool alt_launcher_native_crt(void)
@@ -529,19 +580,19 @@ void alt_launcher_poll(void)
 {
 	if (s_pid)
 	{
+		if (s_native_crt && s_native_crt_finish_timer && CheckTimer(s_native_crt_finish_timer))
+		{
+			finish_native_crt_path();
+			printf("alt_launcher: native CRT path enabled\n");
+		}
+
 		if (s_native_crt && s_native_status_timer && CheckTimer(s_native_status_timer))
 		{
 			user_io_status_set("[9]", 1);
 			s_native_status_timer = GetTimer(500);
 			if (!s_native_status_timer) s_native_status_timer = 1;
 		}
 
-		if (s_native_crt && s_native_fb_mode_timer && CheckTimer(s_native_fb_mode_timer))
-		{
-			set_native_crt_fb_mode();
-			s_native_fb_mode_timer = 0;
-		}
-
 		int status;
 		if (waitpid(s_pid, &status, WNOHANG) == s_pid)
 		{
@@ -584,7 +635,7 @@ void alt_launcher_poll(void)
 			return;
 		}
 
-		if (s_tty_deadline && (launcher_tty_ready(s_pid) || CheckTimer(s_tty_deadline)))
+		if (s_tty_deadline && !s_native_crt_finish_timer && (launcher_tty_ready(s_pid) || CheckTimer(s_tty_deadline)))
 			finalize_spawn();
 		return;
 	}