[patch 051/108] ALSA: intel8x0 - Fix PCM position craziness

Greg KH
2009-07-01T01:00:43Z

[-- Attachment #1: alsa-intel8x0-fix-pcm-position-craziness.patch --]
[-- Type: text/plain, Size: 2842 bytes --]

2.6.30-stable review patch. If anyone has any objections, please let us know.

------------------

From: Takashi Iwai <tiwai@suse.de>

commit f708eb1d71dc8ffb184da9f0bc53461c6dc10653 upstream.

The PCM pointer callback sometimes returns invalid positions and this
screws up the hw_ptr updater in PCM core. Especially since now the
jiffies check is optional with xrun_debug, the invalid position is
handled as is, and causes serious sound skips, etc.

This patch simplifies the position-fix strategy in intel8x0 to be more
robust:
- just falls back to the last position if bogus position is detected
- another sanity check for the backward move of the position due to
a race of register update and the base-index update

This patch is applicable also for 2.6.30.

Tested-by: David Miller <davem@davemloft.net>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
sound/pci/intel8x0.c | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)

--- a/sound/pci/intel8x0.c
+++ b/sound/pci/intel8x0.c
@@ -356,8 +356,6 @@ struct ichdev {
unsigned int position;
unsigned int pos_shift;
unsigned int last_pos;
- unsigned long last_pos_jiffies;
- unsigned int jiffy_to_bytes;
int frags;
int lvi;
int lvi_frag;
@@ -844,7 +842,6 @@ static int snd_intel8x0_pcm_trigger(stru
case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
val = ICH_IOCE | ICH_STARTBM;
ichdev->last_pos = ichdev->position;
- ichdev->last_pos_jiffies = jiffies;
break;
case SNDRV_PCM_TRIGGER_SUSPEND:
ichdev->suspended = 1;
@@ -1048,7 +1045,6 @@ static int snd_intel8x0_pcm_prepare(stru
ichdev->pos_shift = (runtime->sample_bits > 16) ? 2 : 1;
}
snd_intel8x0_setup_periods(chip, ichdev);
- ichdev->jiffy_to_bytes = (runtime->rate * 4 * ichdev->pos_shift) / HZ;
return 0;
}

@@ -1073,19 +1069,23 @@ static snd_pcm_uframes_t snd_intel8x0_pc
ptr1 == igetword(chip, ichdev->reg_offset + ichdev->roff_picb))
break;
} while (timeout--);
+ ptr = ichdev->last_pos;
if (ptr1 != 0) {
ptr1 <<= ichdev->pos_shift;
ptr = ichdev->fragsize1 - ptr1;
ptr += position;
- ichdev->last_pos = ptr;
- ichdev->last_pos_jiffies = jiffies;
- } else {
- ptr1 = jiffies - ichdev->last_pos_jiffies;
- if (ptr1)
- ptr1 -= 1;
- ptr = ichdev->last_pos + ptr1 * ichdev->jiffy_to_bytes;
- ptr %= ichdev->size;
+ if (ptr < ichdev->last_pos) {
+ unsigned int pos_base, last_base;
+ pos_base = position / ichdev->fragsize1;
+ last_base = ichdev->last_pos / ichdev->fragsize1;
+ /* another sanity check; ptr1 can go back to full
+ * before the base position is updated
+ */
+ if (pos_base == last_base)
+ ptr = ichdev->last_pos;
+ }
}
+ ichdev->last_pos = ptr;
spin_unlock(&chip->reg_lock);
if (ptr >= ichdev->size)
return 0;