ALSA: hda - Stop LPIB delay counting on broken hardware

If LPIB reports a pretty bad value, we can't trust such hardware for
calculating the PCM delay.  Automatically turn off the delay counting
when such a problem is encountered.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=48911

Cc: <stable@vger.kernel.org> [v3.6]
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
index ecf2775..72b085a 100644 (file)
--- a/sound/pci/hda/hda_intel.c
+++ b/sound/pci/hda/hda_intel.c
@@ -2158,9 +2158,12 @@ static unsigned int azx_get_position(struct azx *chip,
                if (delay < 0)
                        delay += azx_dev->bufsize;
                if (delay >= azx_dev->period_bytes) {
-                       snd_printdd("delay %d > period_bytes %d\n",
-                               delay, azx_dev->period_bytes);
-                       delay = 0; /* something is wrong */
+                       snd_printk(KERN_WARNING SFX
+                                  "Unstable LPIB (%d >= %d); "
+                                  "disabling LPIB delay counting\n",
+                                  delay, azx_dev->period_bytes);
+                       delay = 0;
+                       chip->driver_caps &= ~AZX_DCAPS_COUNT_LPIB_DELAY;
                }
                azx_dev->substream->runtime->delay =
                        bytes_to_frames(azx_dev->substream->runtime, delay);