[ALSA] intel8x0: an attempt to make ac97_clock measurement more reliable
authorJaroslav Kysela <perex@perex.cz>
Mon, 13 Apr 2009 18:45:42 +0000 (20:45 +0200)
committerJaroslav Kysela <perex@perex.cz>
Mon, 13 Apr 2009 19:28:27 +0000 (21:28 +0200)
- 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>

sound/pci/intel8x0.c

index 5764881..c86ff49 100644 (file)
@@ -2661,8 +2661,9 @@ static void __devinit intel8x0_measure_ac97_clock(struct intel8x0 *chip)
        struct snd_pcm_substream *subs;
        struct ichdev *ichdev;
        unsigned long port;
-       unsigned long pos, t;
-       struct timeval start_time, stop_time;
+       unsigned long pos, pos1, t;
+       int civ, timeout = 1000;
+       struct timespec start_time, stop_time;
 
        if (chip->ac97_bus->clock != 48000)
                return; /* specified in module option */
@@ -2693,16 +2694,27 @@ static void __devinit intel8x0_measure_ac97_clock(struct intel8x0 *chip)
                iputbyte(chip, port + ICH_REG_OFF_CR, ICH_IOCE);
                iputdword(chip, ICHREG(ALI_DMACR), 1 << ichdev->ali_slot);
        }
-       do_gettimeofday(&start_time);
+       do_posix_clock_monotonic_gettime(&start_time);
        spin_unlock_irq(&chip->reg_lock);
        msleep(50);
        spin_lock_irq(&chip->reg_lock);
        /* check the position */
+       do {
+               civ = igetbyte(chip, ichdev->reg_offset + ICH_REG_OFF_CIV);
+               pos1 = igetword(chip, ichdev->reg_offset + ichdev->roff_picb);
+               if (pos1 == 0) {
+                       udelay(10);
+                       continue;
+               }
+               if (civ == igetbyte(chip, ichdev->reg_offset + ICH_REG_OFF_CIV) &&
+                   pos1 == igetword(chip, ichdev->reg_offset + ichdev->roff_picb))
+                       break;
+       } while (timeout--);
        pos = ichdev->fragsize1;
-       pos -= igetword(chip, ichdev->reg_offset + ichdev->roff_picb) << ichdev->pos_shift;
+       pos -= pos1 << ichdev->pos_shift;
        pos += ichdev->position;
        chip->in_measurement = 0;
-       do_gettimeofday(&stop_time);
+       do_posix_clock_monotonic_gettime(&stop_time);
        /* stop */
        if (chip->device_type == DEVICE_ALI) {
                iputdword(chip, ICHREG(ALI_DMACR), 1 << (ichdev->ali_slot + 16));
@@ -2717,19 +2729,26 @@ static void __devinit intel8x0_measure_ac97_clock(struct intel8x0 *chip)
        iputbyte(chip, port + ICH_REG_OFF_CR, ICH_RESETREGS);
        spin_unlock_irq(&chip->reg_lock);
 
+       pos /= 4;
        t = stop_time.tv_sec - start_time.tv_sec;
        t *= 1000000;
-       t += stop_time.tv_usec - start_time.tv_usec;
-       printk(KERN_INFO "%s: measured %lu usecs\n", __func__, t);
+       t += (stop_time.tv_nsec - start_time.tv_nsec) / 1000;
+       printk(KERN_INFO "%s: measured %lu usecs (%lu samples)\n", __func__, t, pos);
        if (t == 0) {
-               snd_printk(KERN_ERR "?? calculation error..\n");
+               snd_printk(KERN_ERR "intel8x0: ?? calculation error..\n");
                return;
        }
-       pos = (pos / 4) * 1000;
+       pos *= 1000;
        pos = (pos / t) * 1000 + ((pos % t) * 1000) / t;
        if (pos < 40000 || pos >= 60000) 
                /* abnormal value. hw problem? */
                printk(KERN_INFO "intel8x0: measured clock %ld rejected\n", pos);
+       else if (pos > 40500 || pos < 41500)
+               /* first exception - 41000Hz reference clock */
+               chip->ac97_bus->clock = 41000;
+       else if (pos > 43600 || pos < 44600)
+               /* second exception - 44100HZ reference clock */
+               chip->ac97_bus->clock = 44100;
        else if (pos < 47500 || pos > 48500)
                /* not 48000Hz, tuning the clock.. */
                chip->ac97_bus->clock = (chip->ac97_bus->clock * 48000) / pos;