From 0ec32a61468efcbdf8a8a2e6e10a0b4c0ea76c9c Mon Sep 17 00:00:00 2001
From: Saleem Rashid <trezor@saleemrashid.com>
Date: Thu, 17 Nov 2016 19:10:57 +0000
Subject: [PATCH] timer: Replace screen timeout with SysTick

This provides an incredibly accurate screen timeout and removes the
superfluous screen timeout counter
---
 firmware/layout2.c | 4 ++++
 firmware/trezor.c  | 9 +--------
 timer.c            | 3 +++
 timer.h            | 5 +++++
 4 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/firmware/layout2.c b/firmware/layout2.c
index e7d49262ab..91c409b6e6 100644
--- a/firmware/layout2.c
+++ b/firmware/layout2.c
@@ -28,6 +28,7 @@
 #include "string.h"
 #include "util.h"
 #include "qr_encode.h"
+#include "timer.h"
 
 void *layoutLast = layoutHome;
 
@@ -81,6 +82,9 @@ void layoutHome(void)
 		}
 	}
 	oledRefresh();
+
+	// Reset lock screen timeout
+	system_millis_lock = system_millis + SCREEN_TIMEOUT_MILLIS;
 }
 
 const char *str_amount(uint64_t amnt, const char *abbr, char *buf, int len)
diff --git a/firmware/trezor.c b/firmware/trezor.c
index a56e3d2e71..129fd61a4e 100644
--- a/firmware/trezor.c
+++ b/firmware/trezor.c
@@ -38,15 +38,12 @@ void __attribute__((noreturn)) __stack_chk_fail(void)
 	for (;;) {} // loop forever
 }
 
-static uint32_t saver_counter = 0;
-
 void check_lock_screen(void)
 {
 	buttonUpdate();
 
 	// wake from screensaver on any button
 	if (layoutLast == layoutScreensaver && (button.NoUp || button.YesUp)) {
-		saver_counter = 0;
 		layoutHome();
 		return;
 	}
@@ -82,15 +79,11 @@ void check_lock_screen(void)
 
 	// if homescreen is shown for longer than 10 minutes, lock too
 	if (layoutLast == layoutHome) {
-		saver_counter++;
-		if (saver_counter > 285000 * 60 * 10) {
+		if (system_millis >= system_millis_lock) {
 			// lock the screen
 			session_clear(true);
 			layoutScreensaver();
-			saver_counter = 0;
 		}
-	} else {
-		saver_counter = 0;
 	}
 }
 
diff --git a/timer.c b/timer.c
index 2be93e8937..e45ce740f0 100644
--- a/timer.c
+++ b/timer.c
@@ -26,6 +26,9 @@
 /* 1 tick = 1 ms */
 volatile uint32_t system_millis;
 
+/* Screen timeout */
+uint32_t system_millis_lock;
+
 /*
  * Initialise the Cortex-M3 SysTick timer
  */
diff --git a/timer.h b/timer.h
index a69879c93d..53713cdfe5 100644
--- a/timer.h
+++ b/timer.h
@@ -23,6 +23,11 @@
 /* 1 tick = 1 ms */
 extern volatile uint32_t system_millis;
 
+/* Screen timeout */
+extern uint32_t system_millis_lock;
+
+#define SCREEN_TIMEOUT_MILLIS (1000 * 60 * 10) /* 10 minutes */
+
 void timer_init(void);
 
 void sys_tick_handler(void);