From 1582bad2d65c9bae75ee3715b2737341b7fc63ee Mon Sep 17 00:00:00 2001
From: Sebastien Bourdeauducq <sebastien@milkymist.org>
Date: Wed, 13 Nov 2013 16:50:09 +0100
Subject: [PATCH] videomixer: filter PLL lock output

---
 software/libbase/time.c           |  4 ++++
 software/videomixer/dvisamplerX.c | 31 +++++++++++++++++++++++++++----
 2 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/software/libbase/time.c b/software/libbase/time.c
index c1c2ea8b8..c809dfd54 100644
--- a/software/libbase/time.c
+++ b/software/libbase/time.c
@@ -18,6 +18,10 @@ int elapsed(int *last_event, int period)
 
 	timer0_update_value_write(1);
 	t = timer0_reload_read() - timer0_value_read();
+	if(period < 0) {
+		*last_event = t;
+		return 1;
+	}
 	dt = t - *last_event;
 	if(dt < 0)
 		dt += timer0_reload_read();
diff --git a/software/videomixer/dvisamplerX.c b/software/videomixer/dvisamplerX.c
index bdb486ac3..c1570a8fc 100644
--- a/software/videomixer/dvisamplerX.c
+++ b/software/videomixer/dvisamplerX.c
@@ -233,10 +233,33 @@ static void dvisamplerX_check_overflow(void)
 	}
 }
 
-static int dvisamplerX_last_event;
+static int dvisamplerX_clocking_locked_filtered(void)
+{
+	static int lock_start_time;
+	static int lock_status;
+
+	if(dvisamplerX_clocking_locked_read()) {
+		switch(lock_status) {
+			case 0:
+				elapsed(&lock_start_time, -1);
+				lock_status = 1;
+				break;
+			case 1:
+				if(elapsed(&lock_start_time, identifier_frequency_read()/4))
+					lock_status = 2;
+				break;
+			case 2:
+				return 1;
+		}
+	} else
+		lock_status = 0;
+	return 0;
+}
 
 void dvisamplerX_service(void)
 {
+	static int last_event;
+
 	if(dvisamplerX_connected) {
 		if(!dvisamplerX_edid_hpd_notif_read()) {
 			if(dvisamplerX_debug)
@@ -246,8 +269,8 @@ void dvisamplerX_service(void)
 			dvisamplerX_clocking_pll_reset_write(1);
 		} else {
 			if(dvisamplerX_locked) {
-				if(dvisamplerX_clocking_locked_read()) {
-					if(elapsed(&dvisamplerX_last_event, identifier_frequency_read()/2)) {
+				if(dvisamplerX_clocking_locked_filtered()) {
+					if(elapsed(&last_event, identifier_frequency_read()/2)) {
 						dvisamplerX_adjust_phase();
 						if(dvisamplerX_debug)
 							dvisamplerX_print_status();
@@ -258,7 +281,7 @@ void dvisamplerX_service(void)
 					dvisamplerX_locked = 0;
 				}
 			} else {
-				if(dvisamplerX_clocking_locked_read()) {
+				if(dvisamplerX_clocking_locked_filtered()) {
 					if(dvisamplerX_debug)
 						printf("dvisamplerX: PLL locked\n");
 					dvisamplerX_phase_startup();