ALSA: intel8x0: Improve comments for VM optimization
The recently merged 228cf79376f1 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>
diff --git a/sound/pci/intel8x0.c b/sound/pci/intel8x0.c
index 29e3125..c3b9bd0 100644
--- a/sound/pci/intel8x0.c
+++ b/sound/pci/intel8x0.c
@@ -1077,6 +1077,13 @@
}
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))