Moved implementation of user timer to the firmware layer, implemented it for iriver, and made it shareable based on priorities. On iriver, the user timer is shared between the backlight fading and other use, so if a plugin registers the timer, the backlight will resort to simple on/off switching until the plugin releases the timer again. Sorted and bumped the plugin api.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@7242 a1c6a512-1295-4272-9138-f99709370657

12 files changed, 335 insertions, 200 deletions

diff --git a/apps/plugin.c b/apps/plugin.c
index 7bfa0e2..6c01806 100644
--- a/apps/plugin.c
+++ b/apps/plugin.c
@@ -45,6 +45,7 @@
 #include "mp3data.h"
 #include "powermgmt.h"
 #include "system.h"
+#include "timer.h"
 #include "sound.h"
 #include "database.h"
 #if (CONFIG_HWCODEC == MASNONE)
@@ -74,9 +75,6 @@ extern unsigned char pluginbuf[];
 /* for actual plugins only, not for codecs */
 static bool plugin_loaded = false;
 static int  plugin_size = 0;
-#ifndef SIMULATOR
-static void (*pfn_timer)(void) = NULL; /* user timer handler */
-#endif
 static void (*pfn_tsr_exit)(void) = NULL; /* TSR exit callback */
 
 static int plugin_test(int api_version, int model, int memsize);
@@ -116,6 +114,14 @@ static const struct plugin_api rockbox_api = {
     lcd_fillrect,
     lcd_mono_bitmap_part,
     lcd_mono_bitmap,
+#if LCD_DEPTH > 1
+    lcd_set_foreground,
+    lcd_get_foreground,
+    lcd_set_background,
+    lcd_get_background,
+    lcd_bitmap_part,
+    lcd_bitmap,
+#endif
     lcd_putsxy,
     lcd_puts_style,
     lcd_puts_scroll_style,
@@ -126,6 +132,7 @@ static const struct plugin_api rockbox_api = {
     scrollbar,
     checkbox,
     font_get,
+    font_getstringsize,
 #endif
     backlight_on,
     backlight_off,
@@ -211,6 +218,9 @@ static const struct plugin_api rockbox_api = {
 #ifdef HAVE_ADJUSTABLE_CPU_FREQ
     cpu_boost,
 #endif
+    timer_register,
+    timer_unregister,
+    timer_set_period,
 #endif
 
     /* strings and memory */
@@ -220,6 +230,7 @@ static const struct plugin_api rockbox_api = {
     strlen,
     strrchr,
     strcmp,
+    strncmp,
     strcasecmp,
     strncasecmp,
     memset,
@@ -289,6 +300,10 @@ static const struct plugin_api rockbox_api = {
     &tagdb_fd,
     &tagdb_initialized,
     tagdb_init,
+    /* runtime database */
+    &rundbheader,
+    &rundb_fd,
+    &rundb_initialized,            
 
     /* misc */
     srand,
@@ -299,14 +314,13 @@ static const struct plugin_api rockbox_api = {
     set_time,
     plugin_get_buffer,
     plugin_get_audio_buffer,
-#ifndef SIMULATOR
-    plugin_register_timer,
-    plugin_unregister_timer,
-#endif
     plugin_tsr,
 #if defined(DEBUG) || defined(SIMULATOR)
     debugf,
 #endif
+#ifdef ROCKBOX_HAS_LOGF
+    logf,
+#endif
     &global_settings,
     mp3info,
     count_mp3_frames,
@@ -326,24 +340,6 @@ static const struct plugin_api rockbox_api = {
     /* new stuff at the end, sort into place next time
        the API gets incompatible */
 
-#ifdef ROCKBOX_HAS_LOGF
-    logf,
-#endif
-    &rundbheader,
-    &rundb_fd,
-    &rundb_initialized,            
-    strncmp,
-#if LCD_DEPTH > 1
-    lcd_set_foreground,
-    lcd_get_foreground,
-    lcd_set_background,
-    lcd_get_background,
-    lcd_bitmap_part,
-    lcd_bitmap,
-#endif
-#ifdef HAVE_LCD_BITMAP
-    font_getstringsize,
-#endif
 };
 
 int plugin_load(const char* plugin, void* parameter)
@@ -486,68 +482,6 @@ void* plugin_get_audio_buffer(int* buffer_size)
     return audiobuf;
 }
 
-#ifndef SIMULATOR
-/* Register a periodic time callback, called every "cycles" CPU clocks. 
-   Note that this function will be called in interrupt context! */
-int plugin_register_timer(int cycles, int prio, void (*timer_callback)(void))
-{
-    int phi = 0; /* bits for the prescaler */
-    int prescale = 1;
-
-    while (cycles > 0x10000)
-    {   /* work out the smallest prescaler that makes it fit */
-        phi++;
-        prescale *= 2;
-        cycles /= 2;
-    }
-
-    if (prescale > 8 || cycles == 0 || prio < 1 || prio > 15)
-        return 0; /* error, we can't do such period, bad argument */
-        
-    backlight_allow_timer(false); /* stop backlight from messing with the timer */
-#if CONFIG_CPU == SH7034
-    and_b(~0x10, &TSTR); /* Stop the timer 4 */
-    and_b(~0x10, &TSNC); /* No synchronization */
-    and_b(~0x10, &TMDR); /* Operate normally */
-
-    pfn_timer = timer_callback; /* install 2nd level ISR */
-
-    and_b(~0x01, &TSR4);
-    TIER4 = 0xF9; /* Enable GRA match interrupt */
-
-    GRA4 = (unsigned short)(cycles - 1);
-    TCR4 = 0x20 | phi; /* clear at GRA match, set prescaler */
-    IPRD = (IPRD & 0xFF0F) | prio << 4; /* interrupt priority */
-    or_b(0x10, &TSTR); /* start timer 4 */
-#else
-    pfn_timer = timer_callback;
-#endif
-    return cycles * prescale; /* return the actual period, in CPU clocks */
-}
-
-/* disable the user timer */
-void plugin_unregister_timer(void)
-{
-#if CONFIG_CPU == SH7034
-    and_b(~0x10, &TSTR); /* stop the timer 4 */
-    IPRD = (IPRD & 0xFF0F); /* disable interrupt */
-    pfn_timer = NULL;
-#endif
-    backlight_allow_timer(true);
-}
-
-#if CONFIG_CPU == SH7034
-/* interrupt handler for user timer */
-#pragma interrupt
-void IMIA4(void)
-{
-    if (pfn_timer != NULL)
-        pfn_timer(); /* call the user timer function */
-    and_b(~0x01, &TSR4); /* clear the interrupt */
-}
-#endif /* CONFIG_CPU == SH7034 */
-#endif /* #ifndef SIMULATOR */
-
 /* The plugin wants to stay resident after leaving its main function, e.g.
    runs from timer or own thread. The callback is registered to later 
    instruct it to free its resources before a new plugin gets loaded. */
diff --git a/apps/plugin.h b/apps/plugin.h
index f504bac..7cda354 100644
--- a/apps/plugin.h
+++ b/apps/plugin.h
@@ -48,6 +48,7 @@
 #include "pcm_playback.h"
 #endif
 #include "settings.h"
+#include "timer.h"
 #include "thread.h"
 #include "playlist.h"
 #ifdef HAVE_LCD_BITMAP
@@ -87,12 +88,12 @@
 #endif
 
 /* increase this every time the api struct changes */
-#define PLUGIN_API_VERSION 46
+#define PLUGIN_API_VERSION 47
 
 /* update this to latest version if a change to the api struct breaks
    backwards compatibility (and please take the opportunity to sort in any 
    new function which are "waiting" at the end of the function table) */
-#define PLUGIN_MIN_API_VERSION 42
+#define PLUGIN_MIN_API_VERSION 47
 
 /* plugin return codes */
 enum plugin_status {
@@ -168,6 +169,23 @@ struct plugin_api {
                                  int stride, int x, int y, int width, int height);
     void (*lcd_mono_bitmap)(const unsigned char *src, int x, int y,
                             int width, int height);
+#if LCD_DEPTH > 1
+#ifdef HAVE_LCD_COLOR
+    void       (*lcd_set_foreground)(struct rgb color);
+    struct rgb (*lcd_get_foreground)(void);
+    void       (*lcd_set_background)(struct rgb color);
+    struct rgb (*lcd_get_background)(void);
+#else
+    void (*lcd_set_foreground)(int brightness);
+    int  (*lcd_get_foreground)(void);
+    void (*lcd_set_background)(int brightness);
+    int  (*lcd_get_background)(void);
+#endif
+    void (*lcd_bitmap_part)(const unsigned char *src, int src_x, int src_y,
+                            int stride, int x, int y, int width, int height);
+    void (*lcd_bitmap)(const unsigned char *src, int x, int y, int width,
+                       int height);
+#endif
     void (*lcd_putsxy)(int x, int y, const unsigned char *string);
     void (*lcd_puts_style)(int x, int y, const unsigned char *str, int style);
     void (*lcd_puts_scroll_style)(int x, int y, const unsigned char* string,
@@ -181,6 +199,8 @@ struct plugin_api {
                       int min_shown, int max_shown, int orientation);
     void (*checkbox)(int x, int y, int width, int height, bool checked);
     struct font* (*font_get)(int font);
+    int  (*font_getstringsize)(const unsigned char *str, int *w, int *h,
+                               int fontnumber);
 #endif
     void (*backlight_on)(void);
     void (*backlight_off)(void);
@@ -272,6 +292,11 @@ struct plugin_api {
 #ifdef HAVE_ADJUSTABLE_CPU_FREQ
     void (*cpu_boost)(bool on_off);
 #endif
+    bool (*timer_register)(int reg_prio, void (*unregister_callback)(void),
+                           long cycles, int int_prio,
+                           void (*timer_callback)(void));
+    void (*timer_unregister)(void);
+    bool (*timer_set_period)(long count);
 #endif
 
     /* strings and memory */
@@ -281,6 +306,7 @@ struct plugin_api {
     size_t (*strlen)(const char *str);
     char * (*strrchr)(const char *s, int c);
     int (*strcmp)(const char *, const char *);
+    int (*strncmp)(const char *, const char *, size_t);
     int (*strcasecmp)(const char *, const char *);
     int (*strncasecmp)(const char *s1, const char *s2, size_t n);
     void* (*memset)(void *dst, int c, size_t length);
@@ -350,6 +376,10 @@ struct plugin_api {
     int *tagdb_fd;
     int *tagdb_initialized;
     int (*tagdb_init) (void);
+    /* runtime database */
+    struct rundb_header *rundbheader;
+    int *rundb_fd;
+    int *rundb_initialized;            
 
     /* misc */
     void (*srand)(unsigned int seed);
@@ -361,14 +391,13 @@ struct plugin_api {
     int  (*set_time)(const struct tm *tm);
     void* (*plugin_get_buffer)(int* buffer_size);
     void* (*plugin_get_audio_buffer)(int* buffer_size);
-#ifndef SIMULATOR
-    int (*plugin_register_timer)(int cycles, int prio, void (*timer_callback)(void));
-    void (*plugin_unregister_timer)(void);
-#endif
     void (*plugin_tsr)(void (*exit_callback)(void));
 #if defined(DEBUG) || defined(SIMULATOR)
     void (*debugf)(const char *fmt, ...);
 #endif
+#ifdef ROCKBOX_HAS_LOGF
+    void (*logf)(const char *fmt, ...);
+#endif
     struct user_settings* global_settings;
     bool (*mp3info)(struct mp3entry *entry, const char *filename, bool v1first);
     int (*count_mp3_frames)(int fd, int startpos, int filesize,
@@ -395,41 +424,11 @@ struct plugin_api {
     /* new stuff at the end, sort into place next time
        the API gets incompatible */     
        
-#ifdef ROCKBOX_HAS_LOGF
-    void (*logf)(const char *fmt, ...);
-#endif
-    struct rundb_header *rundbheader;
-    int *rundb_fd;
-    int *rundb_initialized;            
-    int (*strncmp)(const char *, const char *, size_t);
-#if LCD_DEPTH > 1
-#ifdef HAVE_LCD_COLOR
-    void       (*lcd_set_foreground)(struct rgb color);
-    struct rgb (*lcd_get_foreground)(void);
-    void       (*lcd_set_background)(struct rgb color);
-    struct rgb (*lcd_get_background)(void);
-#else
-    void (*lcd_set_foreground)(int brightness);
-    int  (*lcd_get_foreground)(void);
-    void (*lcd_set_background)(int brightness);
-    int  (*lcd_get_background)(void);
-#endif
-    void (*lcd_bitmap_part)(const unsigned char *src, int src_x, int src_y,
-                            int stride, int x, int y, int width, int height);
-    void (*lcd_bitmap)(const unsigned char *src, int x, int y, int width,
-                       int height);
-#endif
-#ifdef HAVE_LCD_BITMAP
-    int (*font_getstringsize)(const unsigned char *str, int *w, int *h,
-                              int fontnumber);
-#endif
 };
 
 int plugin_load(const char* plugin, void* parameter);
 void* plugin_get_buffer(int *buffer_size);
 void* plugin_get_audio_buffer(int *buffer_size);
-int plugin_register_timer(int cycles, int prio, void (*timer_callback)(void));
-void plugin_unregister_timer(void);
 void plugin_tsr(void (*exit_callback)(void));
 
 /* defined by the plugin */
diff --git a/apps/plugins/alpine_cdc.c b/apps/plugins/alpine_cdc.c
index 7c014a2..5dd8b4a 100644
--- a/apps/plugins/alpine_cdc.c
+++ b/apps/plugins/alpine_cdc.c
@@ -230,15 +230,15 @@ void timer_set_mode(int mode)
 
     if (mode == TM_RX_TIMEOUT)
     {
-        rb->plugin_register_timer(gTimer.timeout, 11, timer4_isr);
+        rb->timer_register(1, NULL, gTimer.timeout, 11, timer4_isr);
     }
     else if (mode == TM_TRANSMIT)
     {
-        rb->plugin_register_timer(gTimer.transmit, 14, timer4_isr);
+        rb->timer_register(1, NULL, gTimer.transmit, 14, timer4_isr);
     }
     else
     {
-        rb->plugin_unregister_timer();
+        rb->timer_unregister();
     }
 }
 
@@ -252,7 +252,7 @@ void timer4_isr(void) /* IMIA4 */
         break;
     case TM_RX_TIMEOUT:
         receive_timeout_isr();
-        rb->plugin_unregister_timer(); /* single shot */
+        rb->timer_unregister(); /* single shot */
         break;
     default:
         timer_set_mode(TM_OFF); /* spurious interrupt */
diff --git a/apps/plugins/lib/gray_core.c b/apps/plugins/lib/gray_core.c
index 18b9c3c..361b392 100644
--- a/apps/plugins/lib/gray_core.c
+++ b/apps/plugins/lib/gray_core.c
@@ -257,11 +257,11 @@ void gray_show(bool enable)
     if (enable)
     {
         _gray_info.flags |= _GRAY_RUNNING;
-        _gray_rb->plugin_register_timer(FREQ / 67, 1, _timer_isr);
+        _gray_rb->timer_register(1, NULL, FREQ / 67, 1, _timer_isr);
     }
     else
     {
-        _gray_rb->plugin_unregister_timer();
+        _gray_rb->timer_unregister();
         _gray_info.flags &= ~_GRAY_RUNNING;
         _gray_rb->lcd_update(); /* restore whatever there was before */
     }
diff --git a/apps/plugins/metronome.c b/apps/plugins/metronome.c
index 3793fd9..fa5520b 100644
--- a/apps/plugins/metronome.c
+++ b/apps/plugins/metronome.c
@@ -235,7 +235,7 @@ void cleanup(void *parameter)
 {
     (void)parameter;
 
-    rb->plugin_unregister_timer();
+    rb->timer_unregister();
     rb->mp3_play_stop(); /* stop audio ISR */
     led(0);
 }
@@ -278,7 +278,7 @@ enum plugin_status plugin_start(struct plugin_api* api, void* parameter){
         rb->mp3_play_stop(); // stop audio ISR
 
     calc_period();
-    rb->plugin_register_timer(((*rb->cpu_frequency)/1024), 1, timer_callback);
+    rb->timer_register(1, NULL, (*rb->cpu_frequency)/1024, 1, timer_callback);
 
     draw_display();
 
diff --git a/apps/plugins/oscilloscope.c b/apps/plugins/oscilloscope.c
index ae77f33..f5e5189 100644
--- a/apps/plugins/oscilloscope.c
+++ b/apps/plugins/oscilloscope.c
@@ -192,7 +192,7 @@ void cleanup(void *parameter)
 {
     (void)parameter;
 
-    rb->plugin_unregister_timer();
+    rb->timer_unregister();
 }
 
 enum plugin_status plugin_start(struct plugin_api* api, void* parameter)
@@ -205,7 +205,7 @@ enum plugin_status plugin_start(struct plugin_api* api, void* parameter)
     (void)parameter;
     rb = api;
     
-    rb->plugin_register_timer(FREQ / 67, 1, timer_isr);
+    rb->timer_register(1, NULL, FREQ / 67, 1, timer_isr);
 
     while (!exit)
     {
diff --git a/apps/plugins/video.c b/apps/plugins/video.c
index b4b27e0..1a288ee 100644
--- a/apps/plugins/video.c
+++ b/apps/plugins/video.c
@@ -388,7 +388,7 @@ void timer4_isr(void)
             else
             {
                 gPlay.bVideoUnderrun = true;
-                rb->plugin_unregister_timer(); // disable ourselves
+                rb->timer_unregister(); // disable ourselves
                 return; // no data available
             }
         }
@@ -490,7 +490,7 @@ int SeekTo(int fd, int nPos)
     if (gPlay.bHasAudio)
         rb->mp3_play_stop(); // stop audio ISR
     if (gPlay.bHasVideo)
-        rb->plugin_unregister_timer(); // stop the timer
+        rb->timer_unregister(); // stop the timer
 
     rb->lseek(fd, nPos, SEEK_SET);
 
@@ -538,9 +538,9 @@ int SeekTo(int fd, int nPos)
         gPlay.bVideoUnderrun = false;
         // start display interrupt
 #if FREQ == 12000000 /* Ondio speed kludge */
-        rb->plugin_register_timer(gPlay.nFrameTimeAdjusted, 1, timer4_isr);
+        rb->timer_register(1, NULL, gPlay.nFrameTimeAdjusted, 1, timer4_isr);
 #else
-        rb->plugin_register_timer(gFileHdr.video_frametime, 1, timer4_isr);
+        rb->timer_register(1, NULL, gFileHdr.video_frametime, 1, timer4_isr);
 #endif
     }
 
@@ -553,7 +553,7 @@ void Cleanup(void *fd)
     rb->close(*(int*)fd); // close the file
 
     if (gPlay.bHasVideo)
-        rb->plugin_unregister_timer(); // stop video ISR, now I can use the display again
+        rb->timer_unregister(); // stop video ISR, now I can use the display again
 
     if (gPlay.bHasAudio)
         rb->mp3_play_stop(); // stop audio ISR
@@ -705,7 +705,7 @@ int PlayTick(int fd)
                 if (gPlay.bHasAudio)
                     rb->mp3_play_pause(false); // pause audio
                 if (gPlay.bHasVideo)
-                    rb->plugin_unregister_timer(); // stop the timer
+                    rb->timer_unregister(); // stop the timer
             }
             else if (gPlay.state == paused)
             {
@@ -719,10 +719,10 @@ int PlayTick(int fd)
                 if (gPlay.bHasVideo)
                 {   // start the video
 #if FREQ == 12000000 /* Ondio speed kludge */
-                    rb->plugin_register_timer(
+                    rb->timer_register(1, NULL,
                         gPlay.nFrameTimeAdjusted, 1, timer4_isr);
 #else
-                    rb->plugin_register_timer(
+                    rb->timer_register(1, NULL,
                         gFileHdr.video_frametime, 1, timer4_isr);
 #endif
                 }
diff --git a/firmware/SOURCES b/firmware/SOURCES
index 5fbe6be..06b4ce0 100644
--- a/firmware/SOURCES
+++ b/firmware/SOURCES
@@ -101,6 +101,7 @@ hwcompat.c
 kernel.c
 rolo.c
 thread.c
+timer.c
 crt0.S
 #endif  
 mp3_playback.c
diff --git a/firmware/backlight.c b/firmware/backlight.c
index e997cca..25cc045 100644
--- a/firmware/backlight.c
+++ b/firmware/backlight.c
@@ -27,6 +27,7 @@
 #include "usb.h"
 #include "power.h"
 #include "system.h"
+#include "timer.h"
 
 #ifdef HAVE_REMOTE_LCD
 #include "lcd-remote.h"
@@ -66,7 +67,6 @@ static unsigned int remote_backlight_timeout = 5;
 static const char backlight_fade_value[8] = { 0, 1, 2, 4, 6, 8, 10, 20 };
 static int fade_in_count = 1;
 static int fade_out_count = 4;
-static bool timer_allowed = true;
 
 static bool bl_timer_active = false;
 static int bl_dim_current = BL_PWM_COUNT;
@@ -75,44 +75,20 @@ static int bl_pwm_counter = 0;
 static volatile int bl_cycle_counter = 0;
 static enum {DIM_STATE_START, DIM_STATE_MAIN} bl_dim_state = DIM_STATE_START;
 
-void backlight_start_timer(void)
-{
-    unsigned int count;
-    
-    if (bl_timer_active)
-        return ;
-        
-    /* Prevent cpu frequency changes while dimming. */
-    cpu_boost(true);
-    count = 1;
-    bl_timer_active = true;
-
-    /* We are using timer 1 */
-    TRR1 = count; /* The reference count */
-    TCN1 = 0; /* reset the timer */
-    TMR1 = 0x011d; /* prescaler=2, restart, CLK/16, enabled */
-
-    TER1 = 0xff; /* Clear all events */
-    
-    /* ICR2 (Timer2) */
-    ICR0 = (ICR0 & 0xffff00ff) | 0x00009000; /* Interrupt on level 4.0 */
-    IMR &= ~(1<<10);
-}
-
-void TIMER1(void) __attribute__ ((interrupt_handler));
-void TIMER1(void)
+static void backlight_isr(void)
 {
     int timer_period;
     bool idle = false;
-
-    timer_period = FREQ / 2000 * BL_PWM_INTERVAL / 1000 / 32;
-    switch (bl_dim_state) {
+    
+    timer_period = FREQ / 1000 * BL_PWM_INTERVAL / 1000;
+    switch (bl_dim_state) 
+    {
       /* New cycle */
       case DIM_STATE_START:
         bl_pwm_counter = 0;
         bl_cycle_counter++;
         
-        if (bl_dim_current > 0 && bl_dim_current < BL_PWM_COUNT) 
+        if (bl_dim_current > 0 && bl_dim_current < BL_PWM_COUNT)
         {
             and_l(~0x00020000, &GPIO1_OUT);
             bl_pwm_counter = bl_dim_current;
@@ -125,6 +101,7 @@ void TIMER1(void)
                 and_l(~0x00020000, &GPIO1_OUT);
             else
                 or_l(0x00020000, &GPIO1_OUT);
+
             if (bl_dim_current == bl_dim_target)
                 idle = true;
         }
@@ -137,9 +114,8 @@ void TIMER1(void)
         bl_dim_state = DIM_STATE_START;
         timer_period = timer_period * (BL_PWM_COUNT - bl_pwm_counter) / BL_PWM_COUNT;
         break ;
-
     }
-    
+
     if ((bl_dim_target > bl_dim_current) && (bl_cycle_counter >= fade_in_count))
     {
         bl_dim_current++;
@@ -155,37 +131,50 @@ void TIMER1(void)
     if (idle) 
     {
         cpu_boost(false);
+        timer_unregister();
         bl_timer_active = false;
-        TMR1 = 0;
     }
+    else
+        timer_set_period(timer_period);
+}
 
-    TRR1 = timer_period;
-    TCN1 = 0;
-    TER1 = 0xff; /* Clear all events */
+static void backlight_switch(void)
+{
+    if (bl_dim_target > (BL_PWM_COUNT/2))
+    {
+        and_l(~0x00020000, &GPIO1_OUT);
+        bl_dim_current = BL_PWM_COUNT;
+    }
+    else
+    {
+        or_l(0x00020000, &GPIO1_OUT);
+        bl_dim_current = 0;
+    }
 }
 
-static void __backlight_dim(int value)
+static void backlight_release_timer(void)
 {
-    bl_dim_target = value;
-    backlight_start_timer();
+    cpu_boost(false);
+    timer_unregister();
+    bl_timer_active = false;
+    backlight_switch();
 }
 
-void backlight_allow_timer(bool on)
+static void backlight_dim(int value)
 {
-    timer_allowed = on;
+    bl_dim_target = value;
 
-    if (!timer_allowed && bl_timer_active)
-    {
-        cpu_boost(false);
-        bl_dim_current = bl_dim_target;
-        bl_timer_active = false;
-        TMR1 = 0;
+    if (bl_timer_active)
+        return ;
 
-        if (bl_dim_current)
-            and_l(~0x00020000, &GPIO1_OUT);
-        else
-            or_l(0x00020000, &GPIO1_OUT);
+    if (timer_register(0, backlight_release_timer, 1, 0, backlight_isr))
+    {
+        /* Prevent cpu frequency changes while dimming. */
+        cpu_boost(true);
+        bl_timer_active = true;
     }
+    else
+        backlight_switch();
 }
 
 void backlight_set_fade_in(int index)
@@ -202,8 +191,8 @@ void backlight_set_fade_out(int index)
 static void __backlight_off(void)
 {
 #if CONFIG_BACKLIGHT == BL_IRIVER
-    if (timer_allowed && (fade_out_count > 0))
-        __backlight_dim(0);
+    if (fade_out_count > 0)
+        backlight_dim(0);
     else
     {
         bl_dim_target = bl_dim_current = 0;
@@ -224,8 +213,8 @@ static void __backlight_off(void)
 static void __backlight_on(void)
 {
 #if CONFIG_BACKLIGHT == BL_IRIVER
-    if (timer_allowed && (fade_in_count > 0))
-        __backlight_dim(BL_PWM_COUNT);
+    if (fade_in_count > 0)
+        backlight_dim(BL_PWM_COUNT);
     else
     {
         bl_dim_target = bl_dim_current = BL_PWM_COUNT;
diff --git a/firmware/export/backlight.h b/firmware/export/backlight.h
index 8d1b56c..b2a2448 100644
--- a/firmware/export/backlight.h
+++ b/firmware/export/backlight.h
@@ -30,9 +30,6 @@ void backlight_set_timeout(int index);
 #if CONFIG_BACKLIGHT == BL_IRIVER
 void backlight_set_fade_in(int index);
 void backlight_set_fade_out(int index);
-void backlight_allow_timer(bool on);
-#else
-#define backlight_allow_timer(on)
 #endif
 bool backlight_get_on_when_charging(void);
 void backlight_set_on_when_charging(bool yesno);
diff --git a/firmware/export/timer.h b/firmware/export/timer.h
new file mode 100644
index 0000000..73936ca
--- /dev/null
+++ b/firmware/export/timer.h
@@ -0,0 +1,34 @@
+/***************************************************************************
+*             __________               __   ___.
+*   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+*   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+*   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+*   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+*                     \/            \/     \/    \/            \/
+* $Id$
+*
+* Copyright (C) 2005 Jens Arnold
+*
+* All files in this archive are subject to the GNU General Public License.
+* See the file COPYING in the source tree root for full license agreement.
+*
+* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+* KIND, either express or implied.
+*
+****************************************************************************/
+
+#ifndef __TIMER_H__
+#define __TIMER_H__
+
+#include <stdbool.h>
+#include "config.h"
+
+#ifndef SIMULATOR
+
+bool timer_register(int reg_prio, void (*unregister_callback)(void),
+                    long cycles, int int_prio, void (*timer_callback)(void));
+bool timer_set_period(long cycles);
+void timer_unregister(void);
+
+#endif /* !SIMULATOR */
+#endif /* __TIMER_H__ */
diff --git a/firmware/timer.c b/firmware/timer.c
new file mode 100644
index 0000000..3e524ac
--- /dev/null
+++ b/firmware/timer.c
@@ -0,0 +1,181 @@
+/***************************************************************************
+*             __________               __   ___.
+*   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+*   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+*   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+*   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+*                     \/            \/     \/    \/            \/
+* $Id$
+*
+* Copyright (C) 2005 Jens Arnold
+*
+* All files in this archive are subject to the GNU General Public License.
+* See the file COPYING in the source tree root for full license agreement.
+*
+* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+* KIND, either express or implied.
+*
+****************************************************************************/
+
+#include <stdbool.h>
+#include "config.h"
+#include "cpu.h"
+#include "system.h"
+#include "timer.h"
+
+#ifndef SIMULATOR
+
+static int timer_prio = -1;
+static void (*pfn_timer)(void) = NULL;      /* timer callback */
+static void (*pfn_unregister)(void) = NULL; /* unregister callback */
+
+
+/* interrupt handler */
+#if CONFIG_CPU == SH7034
+void IMIA4(void) __attribute__((interrupt_handler));
+void IMIA4(void)
+{
+    if (pfn_timer != NULL)
+        pfn_timer();
+    and_b(~0x01, &TSR4); /* clear the interrupt */
+}
+#elif defined CPU_COLDFIRE
+void TIMER1(void) __attribute__ ((interrupt_handler));
+void TIMER1(void)
+{
+    if (pfn_timer != NULL)
+        pfn_timer();
+    TER1 = 0xff; /* clear all events */
+}
+#endif /* CONFIG_CPU */
+
+static bool timer_set(long cycles, bool start)
+{
+    int phi = 0; /* bits for the prescaler */
+    int prescale = 1;
+    
+#ifdef CPU_COLDFIRE
+    cycles >>= 1; /* the coldfire timer works on busclk == cpuclk/2 */
+#endif
+
+    while (cycles > 0x10000)
+    {   /* work out the smallest prescaler that makes it fit */
+#if CONFIG_CPU == SH7034
+        phi++;
+#endif
+        prescale *= 2;
+        cycles >>= 1;
+    }
+
+#if CONFIG_CPU == SH7034
+    if (prescale > 8)
+        return false;
+
+    if (start)
+    {
+        if (pfn_unregister != NULL)
+        {
+            pfn_unregister();
+            pfn_unregister = NULL;
+        }
+
+        and_b(~0x10, &TSTR); /* Stop the timer 4 */
+        and_b(~0x10, &TSNC); /* No synchronization */
+        and_b(~0x10, &TMDR); /* Operate normally */
+
+        TIER4 = 0xF9;        /* Enable GRA match interrupt */
+    }
+
+    TCR4 = 0x20 | phi;   /* clear at GRA match, set prescaler */
+    GRA4 = (unsigned short)(cycles - 1);
+    if (start || (TCNT4 >= GRA4))
+        TCNT4 = 0;
+    and_b(~0x01, &TSR4); /* clear an eventual interrupt */
+
+#elif defined CPU_COLDFIRE
+    if (prescale > 4096)
+        return false;
+
+    if (prescale > 256)
+    {
+        phi = 0x05;      /* prescale sysclk/16, timer enabled */
+        prescale >>= 4;
+    }
+    else
+        phi = 0x03;      /* prescale sysclk, timer enabled */
+
+    if (start)
+    {
+        if (pfn_unregister != NULL)
+        {
+            pfn_unregister();
+            pfn_unregister = NULL;
+        }
+        phi &= ~1;       /* timer disabled at start */
+    }
+
+    /* We are using timer 1 */
+    TMR1 = 0x0018 | (unsigned short)phi | ((unsigned short)(prescale - 1) << 8);
+    TRR1 = (unsigned short)(cycles - 1);
+    if (start || (TCN1 >= TRR1))
+        TCN1 = 0; /* reset the timer */
+    TER1 = 0xff;  /* clear all events */
+
+#endif /* CONFIG_CPU */
+    return true;
+}
+
+/* Register a user timer, called every <count> CPU cycles */
+bool timer_register(int reg_prio, void (*unregister_callback)(void),
+                    long cycles, int int_prio, void (*timer_callback)(void))
+{
+    if (reg_prio <= timer_prio || cycles == 0)
+        return false;
+
+#if CONFIG_CPU == SH7034
+    if (int_prio < 1 || int_prio > 15)
+        return false;
+#elif defined CPU_COLDFIRE
+    (void)int_prio;
+#endif
+
+    if (!timer_set(cycles, true))
+        return false;
+        
+    pfn_timer = timer_callback;
+    pfn_unregister = unregister_callback;
+    timer_prio = reg_prio;
+
+#if CONFIG_CPU == SH7034
+    IPRD = (IPRD & 0xFF0F) | int_prio << 4;  /* interrupt priority */
+    or_b(0x10, &TSTR); /* start timer 4 */
+#elif defined CPU_COLDFIRE
+    /* ICR2 (Timer1) */
+    ICR0 = (ICR0 & 0xffff00ff) | 0x00009000; /* interrupt on level 4.0 */
+    and_l(~(1<<10), &IMR);
+    TMR1 |= 1;         /* start timer */
+#endif
+
+    return true;
+}
+
+bool timer_set_period(long cycles)
+{
+    return timer_set(cycles, false);
+}
+
+void timer_unregister(void)
+{
+#if CONFIG_CPU == SH7034
+    and_b(~0x10, &TSTR);    /* stop the timer 4 */
+    IPRD = (IPRD & 0xFF0F); /* disable interrupt */
+#elif defined CPU_COLDFIRE
+    TMR1 = 0;               /* disable timer 1 */
+    or_l((1<<10), &IMR);    /* disable interrupt */
+#endif
+    pfn_timer = NULL;
+    pfn_unregister = NULL;
+    timer_prio = -1;
+}
+
+#endif /* !SIMULATOR */