Commit f708eb1d authored by Takashi Iwai's avatar Takashi Iwai
Browse files

ALSA: intel8x0 - Fix PCM position craziness 



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: default avatarDavid Miller <davem@davemloft.net>
Cc: <stable@kernel.org>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 07a2039b

sound/pci/intel8x0.c

+12 −12
Original line number Diff line number Diff line
@@ -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(struct snd_pcm_substream *substream, int cmd 
	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(struct snd_pcm_substream *substream) 
			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_pcm_pointer(struct snd_pcm_substream *subs 
		    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;

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