diff options
Diffstat (limited to 'Documentation/sound/alsa/Procfile.txt')
| -rw-r--r-- | Documentation/sound/alsa/Procfile.txt | 50 |
1 files changed, 38 insertions, 12 deletions
diff --git a/Documentation/sound/alsa/Procfile.txt b/Documentation/sound/alsa/Procfile.txt index bba2dbb79d8..7fcd1ad96fc 100644 --- a/Documentation/sound/alsa/Procfile.txt +++ b/Documentation/sound/alsa/Procfile.txt @@ -88,21 +88,47 @@ card*/pcm*/info substreams, etc. card*/pcm*/xrun_debug - This file appears when CONFIG_SND_DEBUG=y. - This shows the status of xrun (= buffer overrun/xrun) debug of - ALSA PCM middle layer, as an integer from 0 to 2. The value - can be changed by writing to this file, such as + This file appears when CONFIG_SND_DEBUG=y and + CONFIG_PCM_XRUN_DEBUG=y. + This shows the status of xrun (= buffer overrun/xrun) and + invalid PCM position debug/check of ALSA PCM middle layer. + It takes an integer value, can be changed by writing to this + file, such as + + # echo 5 > /proc/asound/card0/pcm0p/xrun_debug + + The value consists of the following bit flags: + bit 0 = Enable XRUN/jiffies debug messages + bit 1 = Show stack trace at XRUN / jiffies check + bit 2 = Enable additional jiffies check + bit 3 = Log hwptr update at each period interrupt + bit 4 = Log hwptr update at each snd_pcm_update_hw_ptr() + bit 5 = Show last 10 positions on error + bit 6 = Do above only once + + When the bit 0 is set, the driver will show the messages to + kernel log when an xrun is detected. The debug message is + shown also when the invalid H/W pointer is detected at the + update of periods (usually called from the interrupt + handler). - # cat 2 > /proc/asound/card0/pcm0p/xrun_debug + When the bit 1 is set, the driver will show the stack trace + additionally. This may help the debugging. - When this value is greater than 0, the driver will show the - messages to kernel log when an xrun is detected. The debug - message is shown also when the invalid H/W pointer is detected - at the update of periods (usually called from the interrupt - handler). + Since 2.6.30, this option can enable 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. + This feature is enabled via the bit 2. + + Bits 3 and 4 are for logging the hwptr records. Note that + these will give flood of kernel messages. + + When bit 5 is set, the driver logs the last 10 xrun errors and + the proc file shows each jiffies, position, period_size, + buffer_size, old_hw_ptr, and hw_ptr_base values. - When this value is greater than 1, the driver will show the - stack trace additionally. This may help the debugging. + When bit 6 is set, the full xrun log is shown only once. card*/pcm*/sub*/info The general information of this PCM sub-stream. |