redonkable/remarkable-linux
redonkable/remarkable-linux
1
0
Fork 0
Code Releases Activity

[ALSA] intel8x0: an attempt to make ac97_clock measurement more reliable

Browse source 
- 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>
This commit is contained in:
Jaroslav Kysela 2009-04-13 20:45:42 +02:00
parent bbf6ad1399
commit 920e4ae31c
1 changed files with 28 additions and 9 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

37
sound/pci/intel8x0.c
View 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;