Re: [alsa-devel] ALSA: es1968: Use monotonic clock

On Sun, 09 Aug 2015 03:48:23 +0200, Abhilash Jindal wrote:

Wall time obtained from do_gettimeofday is susceptible to sudden jumps due to user setting the time or due to NTP.

Monotonic time is constantly increasing time better suited for comparing two timestamps.

Your sign-off is missing.

Also, if we use ktime, ktime_get_raw_ns() or such would be much easier to use. It'll be a good cleanup in the end.

thanks,

Takashi

---

sound/pci/es1968.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/sound/pci/es1968.c b/sound/pci/es1968.c index b0e3d92..6830c31 100644 --- a/sound/pci/es1968.c +++ b/sound/pci/es1968.c @@ -1710,7 +1710,7 @@ static void es1968_measure_clock(struct es1968 *chip) int i, apu; unsigned int pa, offset, t; struct esm_memory *memory;

• struct timeval start_time, stop_time;

• struct timespec start_time, stop_time;

  if (chip->clock == 0) chip->clock = 48000; /* default clock value */

@@ -1759,12 +1759,12 @@ static void es1968_measure_clock(struct es1968 *chip) snd_es1968_bob_inc(chip, ESM_BOB_FREQ); __apu_set_register(chip, apu, 5, pa & 0xffff); snd_es1968_trigger_apu(chip, apu, ESM_APU_16BITLINEAR);

• do_gettimeofday(&start_time);

• ktime_get_ts(&start_time); spin_unlock_irq(&chip->reg_lock); msleep(50); spin_lock_irq(&chip->reg_lock); offset = __apu_get_register(chip, apu, 5);

• do_gettimeofday(&stop_time);

• ktime_get_ts(&stop_time); snd_es1968_trigger_apu(chip, apu, 0); /* stop */ snd_es1968_bob_dec(chip); chip->in_measurement = 0;

@@ -1776,11 +1776,11 @@ static void es1968_measure_clock(struct es1968 *chip) offset += chip->measure_count * (CLOCK_MEASURE_BUFSIZE/2);

t = stop_time.tv_sec - start_time.tv_sec;

• t *= 1000000;
• if (stop_time.tv_usec < start_time.tv_usec)
• t -= start_time.tv_usec - stop_time.tv_usec;

• t *= USEC_PER_SEC;
• if (stop_time.tv_nsec < start_time.tv_nsec)
• t -= (start_time.tv_nsec - stop_time.tv_nsec)/NSEC_PER_USEC; else

• t += stop_time.tv_usec - start_time.tv_usec;

• t += (stop_time.tv_nsec - start_time.tv_nsec)/NSEC_PER_USEC; if (t == 0) { snd_printk(KERN_ERR "?? calculation error..\n"); } else {

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