[PATCH 08/11] ALSA: vsnd: Add timer for period interrupt emulation

Oleksandr Andrushchenko
2017-08-07T07:45:21Z

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@epam.com>
---
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