ALSA: hda: support for wallclock timestamps
Reuse code from clocksource to handle wall clock counter.
Since wrapparound occurs, the audio timestamp is reinitialized
to zero on a trigger. Synchronized linked devices will
start counting from same reference to avoid any drift.
Max buffer time is limited to 178 seconds to make sure
wall clock counter does not overflow
Wallclock timestamps are disabled on capture streams
until we figure out how to handle digital inputs.
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
index 8fd250d..d96a14e 100644
--- a/sound/pci/hda/hda_intel.c
+++ b/sound/pci/hda/hda_intel.c
@@ -47,6 +47,9 @@
#include <linux/reboot.h>
#include <linux/io.h>
#include <linux/pm_runtime.h>
+#include <linux/clocksource.h>
+#include <linux/time.h>
+
#ifdef CONFIG_X86
/* for snoop control */
#include <asm/pgtable.h>
@@ -419,6 +422,9 @@
unsigned int insufficient :1;
unsigned int wc_marked:1;
unsigned int no_period_wakeup:1;
+
+ struct timecounter azx_tc;
+ struct cyclecounter azx_cc;
};
/* CORB/RIRB */
@@ -1749,6 +1755,64 @@
azx_dev->opened = 0;
}
+static cycle_t azx_cc_read(const struct cyclecounter *cc)
+{
+ struct azx_dev *azx_dev = container_of(cc, struct azx_dev, azx_cc);
+ struct snd_pcm_substream *substream = azx_dev->substream;
+ struct azx_pcm *apcm = snd_pcm_substream_chip(substream);
+ struct azx *chip = apcm->chip;
+
+ return azx_readl(chip, WALLCLK);
+}
+
+static void azx_timecounter_init(struct snd_pcm_substream *substream,
+ bool force, cycle_t last)
+{
+ struct azx_dev *azx_dev = get_azx_dev(substream);
+ struct timecounter *tc = &azx_dev->azx_tc;
+ struct cyclecounter *cc = &azx_dev->azx_cc;
+ u64 nsec;
+
+ cc->read = azx_cc_read;
+ cc->mask = CLOCKSOURCE_MASK(32);
+
+ /*
+ * Converting from 24 MHz to ns means applying a 125/3 factor.
+ * To avoid any saturation issues in intermediate operations,
+ * the 125 factor is applied first. The division is applied
+ * last after reading the timecounter value.
+ * Applying the 1/3 factor as part of the multiplication
+ * requires at least 20 bits for a decent precision, however
+ * overflows occur after about 4 hours or less, not a option.
+ */
+
+ cc->mult = 125; /* saturation after 195 years */
+ cc->shift = 0;
+
+ nsec = 0; /* audio time is elapsed time since trigger */
+ timecounter_init(tc, cc, nsec);
+ if (force)
+ /*
+ * force timecounter to use predefined value,
+ * used for synchronized starts
+ */
+ tc->cycle_last = last;
+}
+
+static int azx_get_wallclock_tstamp(struct snd_pcm_substream *substream,
+ struct timespec *ts)
+{
+ struct azx_dev *azx_dev = get_azx_dev(substream);
+ u64 nsec;
+
+ nsec = timecounter_read(&azx_dev->azx_tc);
+ nsec = div_u64(nsec, 3); /* can be optimized */
+
+ *ts = ns_to_timespec(nsec);
+
+ return 0;
+}
+
static struct snd_pcm_hardware azx_pcm_hw = {
.info = (SNDRV_PCM_INFO_MMAP |
SNDRV_PCM_INFO_INTERLEAVED |
@@ -1758,6 +1822,7 @@
/* SNDRV_PCM_INFO_RESUME |*/
SNDRV_PCM_INFO_PAUSE |
SNDRV_PCM_INFO_SYNC_START |
+ SNDRV_PCM_INFO_HAS_WALL_CLOCK |
SNDRV_PCM_INFO_NO_PERIOD_WAKEUP),
.formats = SNDRV_PCM_FMTBIT_S16_LE,
.rates = SNDRV_PCM_RATE_48000,
@@ -1797,6 +1862,12 @@
runtime->hw.rates = hinfo->rates;
snd_pcm_limit_hw_rates(runtime);
snd_pcm_hw_constraint_integer(runtime, SNDRV_PCM_HW_PARAM_PERIODS);
+
+ /* avoid wrap-around with wall-clock */
+ snd_pcm_hw_constraint_minmax(runtime, SNDRV_PCM_HW_PARAM_BUFFER_TIME,
+ 20,
+ 178000000);
+
if (chip->align_buffer_size)
/* constrain buffer sizes to be multiple of 128
bytes. This is more efficient in terms of memory
@@ -1836,6 +1907,12 @@
mutex_unlock(&chip->open_mutex);
return -EINVAL;
}
+
+ /* disable WALLCLOCK timestamps for capture streams
+ until we figure out how to handle digital inputs */
+ if (substream->stream == SNDRV_PCM_STREAM_CAPTURE)
+ runtime->hw.info &= ~SNDRV_PCM_INFO_HAS_WALL_CLOCK;
+
spin_lock_irqsave(&chip->reg_lock, flags);
azx_dev->substream = substream;
azx_dev->running = 0;
@@ -2072,6 +2149,22 @@
azx_readl(chip, OLD_SSYNC) & ~sbits);
else
azx_writel(chip, SSYNC, azx_readl(chip, SSYNC) & ~sbits);
+ if (start) {
+ azx_timecounter_init(substream, 0, 0);
+ if (nsync > 1) {
+ cycle_t cycle_last;
+
+ /* same start cycle for master and group */
+ azx_dev = get_azx_dev(substream);
+ cycle_last = azx_dev->azx_tc.cycle_last;
+
+ snd_pcm_group_for_each_entry(s, substream) {
+ if (s->pcm->card != substream->pcm->card)
+ continue;
+ azx_timecounter_init(s, 1, cycle_last);
+ }
+ }
+ }
spin_unlock(&chip->reg_lock);
return 0;
}
@@ -2306,6 +2399,7 @@
.prepare = azx_pcm_prepare,
.trigger = azx_pcm_trigger,
.pointer = azx_pcm_pointer,
+ .wall_clock = azx_get_wallclock_tstamp,
.mmap = azx_pcm_mmap,
.page = snd_pcm_sgbuf_ops_page,
};