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