From 09f4c911ed99f5d73f4c005d79cc46d901765a88 Mon Sep 17 00:00:00 2001
From: "Jan \"Yenya\" Kasprzak" <kas@fi.muni.cz>
Date: Tue, 28 May 2013 23:07:31 +0200
Subject: [PATCH] pwm.c: disable when not needed

Timer/Counter 1 eats much power, especially with PLL clock. So let's
try to disable it when no PWM channel is active.
---
 firmware/lights.h |  1 +
 firmware/pwm.c    | 27 +++++++++++++++++++++++++--
 firmware/tmr.c    |  1 +
 3 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/firmware/lights.h b/firmware/lights.h
index 6851509..0705dd1 100644
--- a/firmware/lights.h
+++ b/firmware/lights.h
@@ -42,6 +42,7 @@ void susp_pwm();
 void pwm_off(unsigned char n);
 void pwm_set(unsigned char n, uint16_t stride);
 void pwm_timer();
+void pwm_disable_if_not_needed();
 
 /* tmr.c */
 extern volatile uint16_t jiffies;
diff --git a/firmware/pwm.c b/firmware/pwm.c
index b472273..512268c 100644
--- a/firmware/pwm.c
+++ b/firmware/pwm.c
@@ -1,5 +1,6 @@
 #include <avr/io.h>
 #include <avr/interrupt.h>
+#include <avr/power.h>
 #include <util/delay.h>
 #include <util/atomic.h>
 
@@ -13,6 +14,7 @@
 
 static uint16_t pwm[N_PWMLEDS];
 static volatile unsigned char step;
+static unsigned char channels_running, pll_enabled;
 
 static void enable_pll()
 {
@@ -24,6 +26,8 @@ static void enable_pll()
 	while ((PLLCSR & _BV(PLOCK)) == 0)
 		;
 	PLLCSR |= _BV(PCKE);
+
+	pll_enabled = 1;
 }
 
 void init_pwm()
@@ -31,12 +35,12 @@ void init_pwm()
 	int i;
 
 	step = 0;
+	channels_running = 0;
+	pll_enabled = 0;
 
 	for (i = 0; i < N_PWMLEDS; i++)
 		pwm[i] = 0;
 
-	enable_pll();
-
 	// PWM channel D is inverted, ...
 	TCCR1C = _BV(COM1D1) | _BV(COM1D0) | _BV(PWM1D);
 	// PWM channels A and B are not
@@ -76,6 +80,7 @@ void pwm_off(unsigned char n)
 {
 	ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
 		pwm[n] = 0;
+		channels_running &= ~(1 << n);
 
 		switch (n) {
 		case 0: DDRB &= ~_BV(PB1); break;
@@ -119,6 +124,12 @@ void pwm_set(unsigned char n, uint16_t stride)
 
 	ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
 		pwm[n] = stride;
+		channels_running |= (1 << n);
+
+		if (!pll_enabled) {
+			power_timer1_enable();
+			enable_pll();
+		}
 
 		pwm_update_hw(n);
 
@@ -142,3 +153,15 @@ void pwm_timer()
 			pwm_update_hw(i);
 }
 
+void pwm_disable_if_not_needed()
+{
+	if (channels_running)
+		return;
+
+	pll_enabled = 0;
+	DDRB &= ~(_BV(PB1) | _BV(PB3) | _BV(PB5));
+	PLLCSR &= ~(_BV(PLLE) | _BV(PCKE));
+
+	power_timer1_disable();
+}
+
diff --git a/firmware/tmr.c b/firmware/tmr.c
index 2e61db8..7a31f19 100644
--- a/firmware/tmr.c
+++ b/firmware/tmr.c
@@ -22,6 +22,7 @@ ISR(WDT_vect) {
 
 	timer_check_buttons();
 	patterns_next_tick();
+	pwm_disable_if_not_needed();
 	timer_start_slow_adcs();
 
 	if ((jiffies & 0x7FF) == 0)
-- 
2.39.3