1 files changed, 43 insertions, 35 deletions

diff --git a/sound/drivers/dummy.c b/sound/drivers/dummy.c
index f387d53e5039..0a798bde0d03 100644
--- 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)