[ALSA] intel8x0: an attempt to make ac97_clock measurement more reliable
- use monotonic posix clock to measure time - try to avoid reading zero from PICB (position in current buffer) register - show also measured samples - when clock is near 41000 or 44100, use exactly these values (they appears to be reference clocks for hardware manufacturers) Signed-off-by: Jaroslav Kysela <perex@perex.cz>
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@ -2661,8 +2661,9 @@ static void __devinit intel8x0_measure_ac97_clock(struct intel8x0 *chip)
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struct snd_pcm_substream *subs;
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struct ichdev *ichdev;
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unsigned long port;
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unsigned long pos, t;
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struct timeval start_time, stop_time;
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unsigned long pos, pos1, t;
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int civ, timeout = 1000;
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struct timespec start_time, stop_time;
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if (chip->ac97_bus->clock != 48000)
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return; /* specified in module option */
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@ -2693,16 +2694,27 @@ static void __devinit intel8x0_measure_ac97_clock(struct intel8x0 *chip)
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iputbyte(chip, port + ICH_REG_OFF_CR, ICH_IOCE);
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iputdword(chip, ICHREG(ALI_DMACR), 1 << ichdev->ali_slot);
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}
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do_gettimeofday(&start_time);
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do_posix_clock_monotonic_gettime(&start_time);
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spin_unlock_irq(&chip->reg_lock);
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msleep(50);
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spin_lock_irq(&chip->reg_lock);
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/* check the position */
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do {
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civ = igetbyte(chip, ichdev->reg_offset + ICH_REG_OFF_CIV);
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pos1 = igetword(chip, ichdev->reg_offset + ichdev->roff_picb);
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if (pos1 == 0) {
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udelay(10);
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continue;
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}
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if (civ == igetbyte(chip, ichdev->reg_offset + ICH_REG_OFF_CIV) &&
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pos1 == igetword(chip, ichdev->reg_offset + ichdev->roff_picb))
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break;
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} while (timeout--);
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pos = ichdev->fragsize1;
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pos -= igetword(chip, ichdev->reg_offset + ichdev->roff_picb) << ichdev->pos_shift;
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pos -= pos1 << ichdev->pos_shift;
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pos += ichdev->position;
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chip->in_measurement = 0;
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do_gettimeofday(&stop_time);
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do_posix_clock_monotonic_gettime(&stop_time);
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/* stop */
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if (chip->device_type == DEVICE_ALI) {
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iputdword(chip, ICHREG(ALI_DMACR), 1 << (ichdev->ali_slot + 16));
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@ -2717,19 +2729,26 @@ static void __devinit intel8x0_measure_ac97_clock(struct intel8x0 *chip)
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iputbyte(chip, port + ICH_REG_OFF_CR, ICH_RESETREGS);
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spin_unlock_irq(&chip->reg_lock);
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pos /= 4;
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t = stop_time.tv_sec - start_time.tv_sec;
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t *= 1000000;
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t += stop_time.tv_usec - start_time.tv_usec;
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printk(KERN_INFO "%s: measured %lu usecs\n", __func__, t);
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t += (stop_time.tv_nsec - start_time.tv_nsec) / 1000;
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printk(KERN_INFO "%s: measured %lu usecs (%lu samples)\n", __func__, t, pos);
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if (t == 0) {
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snd_printk(KERN_ERR "?? calculation error..\n");
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snd_printk(KERN_ERR "intel8x0: ?? calculation error..\n");
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return;
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}
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pos = (pos / 4) * 1000;
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pos *= 1000;
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pos = (pos / t) * 1000 + ((pos % t) * 1000) / t;
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if (pos < 40000 || pos >= 60000)
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/* abnormal value. hw problem? */
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printk(KERN_INFO "intel8x0: measured clock %ld rejected\n", pos);
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else if (pos > 40500 || pos < 41500)
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/* first exception - 41000Hz reference clock */
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chip->ac97_bus->clock = 41000;
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else if (pos > 43600 || pos < 44600)
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/* second exception - 44100HZ reference clock */
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chip->ac97_bus->clock = 44100;
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else if (pos < 47500 || pos > 48500)
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/* not 48000Hz, tuning the clock.. */
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chip->ac97_bus->clock = (chip->ac97_bus->clock * 48000) / pos;
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