+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;
+}
+