[Xen-devel] [PATCH RESEND 08/11] ALSA: vsnd: Add timer for period interrupt emulation

[Oleksandr Andrushchenko <andr2000@xxxxxxxxx>]

From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>

Front sound driver has no real interrupts, so
playback/capture period passed interrupt needs to be emulated:
this is done via timer. Add required timer operations,
this is based on sound/drivers/dummy.c.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
---
 sound/drivers/xen-front.c | 121 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 121 insertions(+)

diff --git a/sound/drivers/xen-front.c b/sound/drivers/xen-front.c
index 9f31e6832086..507c5eb343c8 100644
--- a/sound/drivers/xen-front.c
+++ b/sound/drivers/xen-front.c
@@ -67,12 +67,29 @@ struct sh_buf_info {
        size_t vbuffer_sz;
 };
 
+struct sdev_alsa_timer_info {
+       spinlock_t lock;
+       struct timer_list timer;
+       unsigned long base_time;
+       /* fractional sample position (based HZ) */
+       unsigned int frac_pos;
+       unsigned int frac_period_rest;
+       /* buffer_size * HZ */
+       unsigned int frac_buffer_size;
+       /* period_size * HZ */
+       unsigned int frac_period_size;
+       unsigned int rate;
+       int elapsed;
+       struct snd_pcm_substream *substream;
+};
+
 struct sdev_pcm_stream_info {
        int unique_id;
        struct snd_pcm_hardware pcm_hw;
        struct xdrv_evtchnl_info *evt_chnl;
        bool is_open;
        uint8_t req_next_id;
+       struct sdev_alsa_timer_info timer;
        struct sh_buf_info sh_buf;
 };
 
@@ -148,6 +165,110 @@ static struct sdev_pcm_stream_info *sdrv_stream_get(
        return stream;
 }
 
+static inline void sdrv_alsa_timer_rearm(struct sdev_alsa_timer_info *dpcm)
+{
+       mod_timer(&dpcm->timer, jiffies +
+               (dpcm->frac_period_rest + dpcm->rate - 1) / dpcm->rate);
+}
+
+static void sdrv_alsa_timer_update(struct sdev_alsa_timer_info *dpcm)
+{
+       unsigned long delta;
+
+       delta = jiffies - dpcm->base_time;
+       if (!delta)
+               return;
+       dpcm->base_time += delta;
+       delta *= dpcm->rate;
+       dpcm->frac_pos += delta;
+       while (dpcm->frac_pos >= dpcm->frac_buffer_size)
+               dpcm->frac_pos -= dpcm->frac_buffer_size;
+       while (dpcm->frac_period_rest <= delta) {
+               dpcm->elapsed++;
+               dpcm->frac_period_rest += dpcm->frac_period_size;
+       }
+       dpcm->frac_period_rest -= delta;
+}
+
+static int sdrv_alsa_timer_start(struct snd_pcm_substream *substream)
+{
+       struct sdev_pcm_stream_info *stream = sdrv_stream_get(substream);
+       struct sdev_alsa_timer_info *dpcm = &stream->timer;
+
+       spin_lock(&dpcm->lock);
+       dpcm->base_time = jiffies;
+       sdrv_alsa_timer_rearm(dpcm);
+       spin_unlock(&dpcm->lock);
+       return 0;
+}
+
+static int sdrv_alsa_timer_stop(struct snd_pcm_substream *substream)
+{
+       struct sdev_pcm_stream_info *stream = sdrv_stream_get(substream);
+       struct sdev_alsa_timer_info *dpcm = &stream->timer;
+
+       spin_lock(&dpcm->lock);
+       del_timer(&dpcm->timer);
+       spin_unlock(&dpcm->lock);
+       return 0;
+}
+
+static int sdrv_alsa_timer_prepare(struct snd_pcm_substream *substream)
+{
+       struct snd_pcm_runtime *runtime = substream->runtime;
+       struct sdev_pcm_stream_info *stream = sdrv_stream_get(substream);
+       struct sdev_alsa_timer_info *dpcm = &stream->timer;
+
+       dpcm->frac_pos = 0;
+       dpcm->rate = runtime->rate;
+       dpcm->frac_buffer_size = runtime->buffer_size * HZ;
+       dpcm->frac_period_size = runtime->period_size * HZ;
+       dpcm->frac_period_rest = dpcm->frac_period_size;
+       dpcm->elapsed = 0;
+       return 0;
+}
+
+static void sdrv_alsa_timer_callback(unsigned long data)
+{
+       struct sdev_alsa_timer_info *dpcm = (struct sdev_alsa_timer_info *)data;
+       int elapsed;
+
+       spin_lock(&dpcm->lock);
+       sdrv_alsa_timer_update(dpcm);
+       sdrv_alsa_timer_rearm(dpcm);
+       elapsed = dpcm->elapsed;
+       dpcm->elapsed = 0;
+       spin_unlock(&dpcm->lock);
+       if (elapsed)
+               snd_pcm_period_elapsed(dpcm->substream);
+}
+
+static snd_pcm_uframes_t sdrv_alsa_timer_pointer(
+       struct snd_pcm_substream *substream)
+{
+       struct sdev_pcm_stream_info *stream = sdrv_stream_get(substream);
+       struct sdev_alsa_timer_info *dpcm = &stream->timer;
+       snd_pcm_uframes_t pos;
+
+       spin_lock(&dpcm->lock);
+       sdrv_alsa_timer_update(dpcm);
+       pos = dpcm->frac_pos / HZ;
+       spin_unlock(&dpcm->lock);
+       return pos;
+}
+
+static int sdrv_alsa_timer_create(struct snd_pcm_substream *substream)
+{
+       struct sdev_pcm_stream_info *stream = sdrv_stream_get(substream);
+       struct sdev_alsa_timer_info *dpcm = &stream->timer;
+
+       spin_lock_init(&dpcm->lock);
+       dpcm->substream = substream;
+       setup_timer(&dpcm->timer, sdrv_alsa_timer_callback,
+               (unsigned long) dpcm);
+       return 0;
+}
+
 static void sdrv_copy_pcm_hw(struct snd_pcm_hardware *dst,
        struct snd_pcm_hardware *src,
        struct snd_pcm_hardware *ref_pcm_hw)
-- 
2.7.4


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel