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ALSA: intel8x0: Improve comments for VM optimization
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The recently merged 228cf79 looks a bit hackish while it is not.
The change was quite simple. In a virtualized environment the
patch unhacks old kludge introduced for old broken AC97 hardware.

This patch adds proper comment to "unkludge" code.

Signed-off-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: Konstantin Ozerkov <kozerkov@parallels.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
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Denis V. Lunev authored and Takashi Iwai committed Nov 8, 2011
1 parent 1ea6b8f commit 5a9a517
Showing 1 changed file with 7 additions and 0 deletions.
7 changes: 7 additions & 0 deletions sound/pci/intel8x0.c
Original file line number Diff line number Diff line change
Expand Up @@ -1077,6 +1077,13 @@ static snd_pcm_uframes_t snd_intel8x0_pcm_pointer(struct snd_pcm_substream *subs
}
if (civ != igetbyte(chip, ichdev->reg_offset + ICH_REG_OFF_CIV))
continue;

/* IO read operation is very expensive inside virtual machine
* as it is emulated. The probability that subsequent PICB read
* will return different result is high enough to loop till
* timeout here.
* Same CIV is strict enough condition to be sure that PICB
* is valid inside VM on emulated card. */
if (chip->inside_vm)
break;
if (ptr1 == igetword(chip, ichdev->reg_offset + ichdev->roff_picb))
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