ALSA: Enable PCM hw_ptr_jiffies check only in xrun_debug mode

The PCM hw_ptr jiffies check results sometimes in problems when a
hardware doesn't give smooth hw_ptr updates.  So far, au88x0 and some
other drivers appear not working due to this strict check.
However, this check is a nice debug tool, and the capability should be
still kept.

Hence, we disable this check now as default unless the user enables it
by setting the xrun_debug mode to the specific stream via a proc file.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/Documentation/sound/alsa/Procfile.txt b/Documentation/sound/alsa/Procfile.txt
index bba2dbb..cfac20c 100644 (file)
--- a/Documentation/sound/alsa/Procfile.txt
+++ b/Documentation/sound/alsa/Procfile.txt
@@ -104,6 +104,11 @@ card*/pcm*/xrun_debug
        When this value is greater than 1, the driver will show the
        stack trace additionally.  This may help the debugging.
 
        When this value is greater than 1, the driver will show the
        stack trace additionally.  This may help the debugging.
 

+       Since 2.6.30, this option also enables the hwptr check using
+       jiffies.  This detects spontaneous invalid pointer callback
+       values, but can be lead to too much corrections for a (mostly
+       buggy) hardware that doesn't give smooth pointer updates.
+

 card*/pcm*/sub*/info
        The general information of this PCM sub-stream.
 
 card*/pcm*/sub*/info
        The general information of this PCM sub-stream.
 

diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index 3eea98a..d659995 100644 (file)
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -249,6 +249,11 @@ static int snd_pcm_update_hw_ptr_interrupt(struct snd_pcm_substream *substream)
                        new_hw_ptr = hw_base + pos;
                }
        }
                        new_hw_ptr = hw_base + pos;
                }
        }

+
+       /* Do jiffies check only in xrun_debug mode */
+       if (!xrun_debug(substream))
+               goto no_jiffies_check;
+

        /* Skip the jiffies check for hardwares with BATCH flag.
         * Such hardware usually just increases the position at each IRQ,
         * thus it can't give any strange position.
        /* Skip the jiffies check for hardwares with BATCH flag.
         * Such hardware usually just increases the position at each IRQ,
         * thus it can't give any strange position.


@@ -336,7 +341,9 @@ int snd_pcm_update_hw_ptr(struct snd_pcm_substream *substream)
                        hw_base = 0;
                new_hw_ptr = hw_base + pos;
        }
                        hw_base = 0;
                new_hw_ptr = hw_base + pos;
        }

-       if (((delta * HZ) / runtime->rate) > jdelta + HZ/100) {
+       /* Do jiffies check only in xrun_debug mode */
+       if (xrun_debug(substream) &&
+           ((delta * HZ) / runtime->rate) > jdelta + HZ/100) {

                hw_ptr_error(substream,
                             "hw_ptr skipping! "
                             "(pos=%ld, delta=%ld, period=%ld, jdelta=%lu/%lu)\n",
                hw_ptr_error(substream,
                             "hw_ptr skipping! "
                             "(pos=%ld, delta=%ld, period=%ld, jdelta=%lu/%lu)\n",