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ALSA: hda - Add documentation for tracepoints 

Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2011-08-05 12:49:46 +02:00
parent 2ae66c2655
commit d11b7fa3d5
1 changed files with 47 additions and 0 deletions
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47
Documentation/sound/alsa/HD-Audio.txt
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@ -524,6 +524,53 @@ power-saving. See /sys/module/snd_hda_intel/parameters/power_save to
check the current value. If it's non-zero, the feature is turned on.
Tracepoints
~~~~~~~~~~~
The hd-audio driver gives a few basic tracepoints.
`hda:hda_send_cmd` traces each CORB write while `hda:hda_get_response`
traces the response from RIRB (only when read from the codec driver).
`hda:hda_bus_reset` traces the bus-reset due to fatal error, etc, and
`hda:hda_power_down` and `hda:hda_power_up` trace the power down/up
via power-saving behavior.
Enabling all tracepoints can be done like
------------------------------------------------------------------------
# echo 1 > /sys/kernel/debug/tracing/events/hda/enable
------------------------------------------------------------------------
then after some commands, you can traces from
/sys/kernel/debug/tracing/trace file. For example, when you want to
trace what codec command is sent, enable the tracepoint like:
------------------------------------------------------------------------
# cat /sys/kernel/debug/tracing/trace
# tracer: nop
#
# TASK-PID CPU# TIMESTAMP FUNCTION
# | | | | |
<...>-7807 [002] 105147.774889: hda_send_cmd: [0:0] val=e3a019
<...>-7807 [002] 105147.774893: hda_send_cmd: [0:0] val=e39019
<...>-7807 [002] 105147.999542: hda_send_cmd: [0:0] val=e3a01a
<...>-7807 [002] 105147.999543: hda_send_cmd: [0:0] val=e3901a
<...>-26764 [001] 349222.837143: hda_send_cmd: [0:0] val=e3a019
<...>-26764 [001] 349222.837148: hda_send_cmd: [0:0] val=e39019
<...>-26764 [001] 349223.058539: hda_send_cmd: [0:0] val=e3a01a
<...>-26764 [001] 349223.058541: hda_send_cmd: [0:0] val=e3901a
------------------------------------------------------------------------
Here `[0:0]` indicates the card number and the codec address, and
`val` shows the value sent to the codec, respectively. The value is
a packed value, and you can decode it via hda-decode-verb program
included in hda-emu package below. For example, the value e3a019 is
to set the left output-amp value to 25.
------------------------------------------------------------------------
% hda-decode-verb 0xe3a019
raw value = 0x00e3a019
cid = 0, nid = 0x0e, verb = 0x3a0, parm = 0x19
raw value: verb = 0x3a0, parm = 0x19
verbname = set_amp_gain_mute
amp raw val = 0xa019
output, left, idx=0, mute=0, val=25
------------------------------------------------------------------------
Development Tree
~~~~~~~~~~~~~~~~
The latest development codes for HD-audio are found on sound git tree: