ALSA: dummy - Better jiffies handling

[pandora-kernel.git] / sound / drivers / dummy.c

diff --git a/sound/drivers/dummy.c b/sound/drivers/dummy.c
index f387d53..0a798bd 100644 (file)
--- a/sound/drivers/dummy.c
+++ b/sound/drivers/dummy.c
@@ -205,21 +205,43 @@ struct snd_dummy {
 struct dummy_systimer_pcm {
        spinlock_t lock;
        struct timer_list timer;
-       unsigned int pcm_buffer_size;
-       unsigned int pcm_period_size;
-       unsigned int pcm_bps;           /* bytes per second */
-       unsigned int pcm_hz;            /* HZ */
-       unsigned int pcm_irq_pos;       /* IRQ position */
-       unsigned int pcm_buf_pos;       /* position in buffer */
+       unsigned long base_time;
+       unsigned int frac_pos;  /* fractional sample position (based HZ) */
+       unsigned int frac_buffer_size;  /* buffer_size * HZ */
+       unsigned int frac_period_size;  /* period_size * HZ */
+       unsigned int rate;
        struct snd_pcm_substream *substream;
 };
 
+static void dummy_systimer_rearm(struct dummy_systimer_pcm *dpcm)
+{
+       unsigned long frac;
+
+       frac = dpcm->frac_pos % dpcm->frac_period_size;
+       dpcm->timer.expires = jiffies +
+               (dpcm->frac_period_size + dpcm->rate - 1) / dpcm->rate;
+       add_timer(&dpcm->timer);
+}
+
+static void dummy_systimer_update(struct dummy_systimer_pcm *dpcm)
+{
+       unsigned long delta;
+
+       delta = jiffies - dpcm->base_time;
+       if (!delta)
+               return;
+       dpcm->base_time = jiffies;
+       dpcm->frac_pos += delta * dpcm->rate;
+       while (dpcm->frac_pos >= dpcm->frac_buffer_size)
+               dpcm->frac_pos -= dpcm->frac_buffer_size;
+}
+
 static int dummy_systimer_start(struct snd_pcm_substream *substream)
 {
        struct dummy_systimer_pcm *dpcm = substream->runtime->private_data;
        spin_lock(&dpcm->lock);
-       dpcm->timer.expires = 1 + jiffies;
-       add_timer(&dpcm->timer);
+       dpcm->base_time = jiffies;
+       dummy_systimer_rearm(dpcm);
        spin_unlock(&dpcm->lock);
        return 0;
 }
@@ -237,20 +259,11 @@ static int dummy_systimer_prepare(struct snd_pcm_substream *substream)
 {
        struct snd_pcm_runtime *runtime = substream->runtime;
        struct dummy_systimer_pcm *dpcm = runtime->private_data;
-       int bps;
 
-       bps = snd_pcm_format_width(runtime->format) * runtime->rate *
-               runtime->channels / 8;
-
-       if (bps <= 0)
-               return -EINVAL;
-
-       dpcm->pcm_bps = bps;
-       dpcm->pcm_hz = HZ;
-       dpcm->pcm_buffer_size = snd_pcm_lib_buffer_bytes(substream);
-       dpcm->pcm_period_size = snd_pcm_lib_period_bytes(substream);
-       dpcm->pcm_irq_pos = 0;
-       dpcm->pcm_buf_pos = 0;
+       dpcm->frac_pos = 0;
+       dpcm->rate = runtime->rate;
+       dpcm->frac_buffer_size = runtime->buffer_size * HZ;
+       dpcm->frac_period_size = runtime->period_size * HZ;
 
        return 0;
 }
@@ -261,26 +274,21 @@ static void dummy_systimer_callback(unsigned long data)
        unsigned long flags;
        
        spin_lock_irqsave(&dpcm->lock, flags);
-       dpcm->timer.expires = 1 + jiffies;
-       add_timer(&dpcm->timer);
-       dpcm->pcm_irq_pos += dpcm->pcm_bps;
-       dpcm->pcm_buf_pos += dpcm->pcm_bps;
-       dpcm->pcm_buf_pos %= dpcm->pcm_buffer_size * dpcm->pcm_hz;
-       if (dpcm->pcm_irq_pos >= dpcm->pcm_period_size * dpcm->pcm_hz) {
-               dpcm->pcm_irq_pos %= dpcm->pcm_period_size * dpcm->pcm_hz;
-               spin_unlock_irqrestore(&dpcm->lock, flags);
-               snd_pcm_period_elapsed(dpcm->substream);
-       } else
-               spin_unlock_irqrestore(&dpcm->lock, flags);
+       dummy_systimer_update(dpcm);
+       dummy_systimer_rearm(dpcm);
+       spin_unlock_irqrestore(&dpcm->lock, flags);
+       snd_pcm_period_elapsed(dpcm->substream);
 }
 
 static snd_pcm_uframes_t
 dummy_systimer_pointer(struct snd_pcm_substream *substream)
 {
-       struct snd_pcm_runtime *runtime = substream->runtime;
-       struct dummy_systimer_pcm *dpcm = runtime->private_data;
+       struct dummy_systimer_pcm *dpcm = substream->runtime->private_data;
 
-       return bytes_to_frames(runtime, dpcm->pcm_buf_pos / dpcm->pcm_hz);
+       spin_lock(&dpcm->lock);
+       dummy_systimer_update(dpcm);
+       spin_unlock(&dpcm->lock);
+       return dpcm->frac_pos / HZ;
 }
 
 static int dummy_systimer_create(struct snd_pcm_substream *substream)