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authorTakashi Iwai <tiwai@suse.de>2011-08-05 12:49:46 +0200
committerTakashi Iwai <tiwai@suse.de>2011-08-05 12:49:46 +0200
commitd11b7fa3d5b6d4b3a730f563e7b14dfc859c40c6 (patch)
treee83ed31b9e89604ecd3951aaacb4310c95988300 /Documentation/sound
parent2ae66c26550cd94b0e2606a9275eb0ab7070ad0e (diff)
ALSA: hda - Add documentation for tracepoints
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'Documentation/sound')
-rw-r--r--Documentation/sound/alsa/HD-Audio.txt47
1 files changed, 47 insertions, 0 deletions
diff --git a/Documentation/sound/alsa/HD-Audio.txt b/Documentation/sound/alsa/HD-Audio.txt
index c82beb007634..ba2a155f3a30 100644
--- a/Documentation/sound/alsa/HD-Audio.txt
+++ b/Documentation/sound/alsa/HD-Audio.txt
@@ -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: