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Based on kernel version 3.9. Page generated on 2013-05-02 23:14 EST.

	MORE NOTES ON HD-AUDIO DRIVER
	=============================
						Takashi Iwai <tiwai@suse.de>
	
	
	GENERAL
	-------
	
	HD-audio is the new standard on-board audio component on modern PCs
	after AC97.  Although Linux has been supporting HD-audio since long
	time ago, there are often problems with new machines.  A part of the
	problem is broken BIOS, and the rest is the driver implementation.
	This document explains the brief trouble-shooting and debugging
	methods for the	HD-audio hardware.
	
	The HD-audio component consists of two parts: the controller chip and 
	the codec chips on the HD-audio bus.  Linux provides a single driver
	for all controllers, snd-hda-intel.  Although the driver name contains
	a word of a well-known hardware vendor, it's not specific to it but for
	all controller chips by other companies.  Since the HD-audio
	controllers are supposed to be compatible, the single snd-hda-driver
	should work in most cases.  But, not surprisingly, there are known
	bugs and issues specific to each controller type.  The snd-hda-intel
	driver has a bunch of workarounds for these as described below.
	
	A controller may have multiple codecs.  Usually you have one audio
	codec and optionally one modem codec.  In theory, there might be
	multiple audio codecs, e.g. for analog and digital outputs, and the
	driver might not work properly because of conflict of mixer elements.
	This should be fixed in future if such hardware really exists.
	
	The snd-hda-intel driver has several different codec parsers depending
	on the codec.  It has a generic parser as a fallback, but this
	functionality is fairly limited until now.  Instead of the generic
	parser, usually the codec-specific parser (coded in patch_*.c) is used
	for the codec-specific implementations.  The details about the
	codec-specific problems are explained in the later sections.
	
	If you are interested in the deep debugging of HD-audio, read the
	HD-audio specification at first.  The specification is found on
	Intel's web page, for example:
	
	- http://www.intel.com/standards/hdaudio/
	
	
	HD-AUDIO CONTROLLER
	-------------------
	
	DMA-Position Problem
	~~~~~~~~~~~~~~~~~~~~
	The most common problem of the controller is the inaccurate DMA
	pointer reporting.  The DMA pointer for playback and capture can be
	read in two ways, either via a LPIB register or via a position-buffer
	map.  As default the driver tries to read from the io-mapped
	position-buffer, and falls back to LPIB if the position-buffer appears
	dead.  However, this detection isn't perfect on some devices.  In such
	a case, you can change the default method via `position_fix` option.
	
	`position_fix=1` means to use LPIB method explicitly.
	`position_fix=2` means to use the position-buffer.
	`position_fix=3` means to use a combination of both methods, needed
	for some VIA controllers.  The capture stream position is corrected
	by comparing both LPIB and position-buffer values.
	`position_fix=4` is another combination available for all controllers,
	and uses LPIB for the playback and the position-buffer for the capture
	streams.
	0 is the default value for all other
	controllers, the automatic check and fallback to LPIB as described in
	the above.  If you get a problem of repeated sounds, this option might
	help.
	
	In addition to that, every controller is known to be broken regarding
	the wake-up timing.  It wakes up a few samples before actually
	processing the data on the buffer.  This caused a lot of problems, for
	example, with ALSA dmix or JACK.  Since 2.6.27 kernel, the driver puts
	an artificial delay to the wake up timing.  This delay is controlled
	via `bdl_pos_adj` option. 
	
	When `bdl_pos_adj` is a negative value (as default), it's assigned to
	an appropriate value depending on the controller chip.  For Intel
	chips, it'd be 1 while it'd be 32 for others.  Usually this works.
	Only in case it doesn't work and you get warning messages, you should
	change this parameter to other values.
	
	
	Codec-Probing Problem
	~~~~~~~~~~~~~~~~~~~~~
	A less often but a more severe problem is the codec probing.  When
	BIOS reports the available codec slots wrongly, the driver gets
	confused and tries to access the non-existing codec slot.  This often
	results in the total screw-up, and destructs the further communication
	with the codec chips.  The symptom appears usually as error messages
	like:
	------------------------------------------------------------------------
	  hda_intel: azx_get_response timeout, switching to polling mode:
	        last cmd=0x12345678
	  hda_intel: azx_get_response timeout, switching to single_cmd mode:
	        last cmd=0x12345678
	------------------------------------------------------------------------
	
	The first line is a warning, and this is usually relatively harmless.
	It means that the codec response isn't notified via an IRQ.  The
	driver uses explicit polling method to read the response.  It gives
	very slight CPU overhead, but you'd unlikely notice it.
	
	The second line is, however, a fatal error.  If this happens, usually
	it means that something is really wrong.  Most likely you are
	accessing a non-existing codec slot.
	
	Thus, if the second error message appears, try to narrow the probed
	codec slots via `probe_mask` option.  It's a bitmask, and each bit
	corresponds to the codec slot.  For example, to probe only the first
	slot, pass `probe_mask=1`.  For the first and the third slots, pass
	`probe_mask=5` (where 5 = 1 | 4), and so on.
	
	Since 2.6.29 kernel, the driver has a more robust probing method, so
	this error might happen rarely, though.
	
	On a machine with a broken BIOS, sometimes you need to force the
	driver to probe the codec slots the hardware doesn't report for use.
	In such a case, turn the bit 8 (0x100) of `probe_mask` option on.
	Then the rest 8 bits are passed as the codec slots to probe
	unconditionally.  For example, `probe_mask=0x103` will force to probe
	the codec slots 0 and 1 no matter what the hardware reports.
	
	
	Interrupt Handling
	~~~~~~~~~~~~~~~~~~
	HD-audio driver uses MSI as default (if available) since 2.6.33
	kernel as MSI works better on some machines, and in general, it's
	better for performance.  However, Nvidia controllers showed bad
	regressions with MSI (especially in a combination with AMD chipset),
	thus we disabled MSI for them.
	
	There seem also still other devices that don't work with MSI.  If you
	see a regression wrt the sound quality (stuttering, etc) or a lock-up
	in the recent kernel, try to pass `enable_msi=0` option to disable
	MSI.  If it works, you can add the known bad device to the blacklist
	defined in hda_intel.c.  In such a case, please report and give the
	patch back to the upstream developer. 
	
	
	HD-AUDIO CODEC
	--------------
	
	Model Option
	~~~~~~~~~~~~
	The most common problem regarding the HD-audio driver is the
	unsupported codec features or the mismatched device configuration.
	Most of codec-specific code has several preset models, either to
	override the BIOS setup or to provide more comprehensive features.
	
	The driver checks PCI SSID and looks through the static configuration
	table until any matching entry is found.  If you have a new machine,
	you may see a message like below:
	------------------------------------------------------------------------
	    hda_codec: ALC880: BIOS auto-probing.
	------------------------------------------------------------------------
	Meanwhile, in the earlier versions, you would see a message like:
	------------------------------------------------------------------------
	    hda_codec: Unknown model for ALC880, trying auto-probe from BIOS...
	------------------------------------------------------------------------
	Even if you see such a message, DON'T PANIC.  Take a deep breath and
	keep your towel.  First of all, it's an informational message, no
	warning, no error.  This means that the PCI SSID of your device isn't
	listed in the known preset model (white-)list.  But, this doesn't mean
	that the driver is broken.  Many codec-drivers provide the automatic
	configuration mechanism based on the BIOS setup.
	
	The HD-audio codec has usually "pin" widgets, and BIOS sets the default
	configuration of each pin, which indicates the location, the
	connection type, the jack color, etc.  The HD-audio driver can guess
	the right connection judging from these default configuration values.
	However -- some codec-support codes, such as patch_analog.c, don't
	support the automatic probing (yet as of 2.6.28).  And, BIOS is often,
	yes, pretty often broken.  It sets up wrong values and screws up the
	driver.
	
	The preset model (or recently called as "fix-up") is provided
	basically to overcome such a situation.  When the matching preset
	model is found in the white-list, the driver assumes the static
	configuration of that preset with the correct pin setup, etc.
	Thus, if you have a newer machine with a slightly different PCI SSID
	(or codec SSID) from the existing one, you may have a good chance to
	re-use the same model.  You can pass the `model` option to specify the
	preset model instead of PCI (and codec-) SSID look-up.
	
	What `model` option values are available depends on the codec chip.
	Check your codec chip from the codec proc file (see "Codec Proc-File"
	section below).  It will show the vendor/product name of your codec
	chip.  Then, see Documentation/sound/alsa/HD-Audio-Models.txt file,
	the section of HD-audio driver.  You can find a list of codecs
	and `model` options belonging to each codec.  For example, for Realtek
	ALC262 codec chip, pass `model=ultra` for devices that are compatible
	with Samsung Q1 Ultra.
	
	Thus, the first thing you can do for any brand-new, unsupported and
	non-working HD-audio hardware is to check HD-audio codec and several
	different `model` option values.  If you have any luck, some of them
	might suit with your device well.
	
	There are a few special model option values:
	- when 'nofixup' is passed, the device-specific fixups in the codec
	  parser are skipped.
	- when `generic` is passed, the codec-specific parser is skipped and
	  only the generic parser is used.
	
	
	Speaker and Headphone Output
	~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	One of the most frequent (and obvious) bugs with HD-audio is the
	silent output from either or both of a built-in speaker and a
	headphone jack.  In general, you should try a headphone output at
	first.  A speaker output often requires more additional controls like
	the external amplifier bits.  Thus a headphone output has a slightly
	better chance.
	
	Before making a bug report, double-check whether the mixer is set up
	correctly.  The recent version of snd-hda-intel driver provides mostly
	"Master" volume control as well as "Front" volume (where Front
	indicates the front-channels).  In addition, there can be individual
	"Headphone" and "Speaker" controls.
	
	Ditto for the speaker output.  There can be "External Amplifier"
	switch on some codecs.  Turn on this if present.
	
	Another related problem is the automatic mute of speaker output by
	headphone plugging.  This feature is implemented in most cases, but
	not on every preset model or codec-support code.
	
	In anyway, try a different model option if you have such a problem.
	Some other models may match better and give you more matching
	functionality.  If none of the available models works, send a bug
	report.  See the bug report section for details.
	
	If you are masochistic enough to debug the driver problem, note the
	following:
	
	- The speaker (and the headphone, too) output often requires the
	  external amplifier.  This can be set usually via EAPD verb or a
	  certain GPIO.  If the codec pin supports EAPD, you have a better
	  chance via SET_EAPD_BTL verb (0x70c).  On others, GPIO pin (mostly
	  it's either GPIO0 or GPIO1) may turn on/off EAPD.
	- Some Realtek codecs require special vendor-specific coefficients to
	  turn on the amplifier.  See patch_realtek.c.
	- IDT codecs may have extra power-enable/disable controls on each
	  analog pin.  See patch_sigmatel.c.
	- Very rare but some devices don't accept the pin-detection verb until
	  triggered.  Issuing GET_PIN_SENSE verb (0xf09) may result in the
	  codec-communication stall.  Some examples are found in
	  patch_realtek.c.
	
	
	Capture Problems
	~~~~~~~~~~~~~~~~
	The capture problems are often because of missing setups of mixers.
	Thus, before submitting a bug report, make sure that you set up the
	mixer correctly.  For example, both "Capture Volume" and "Capture
	Switch" have to be set properly in addition to the right "Capture
	Source" or "Input Source" selection.  Some devices have "Mic Boost"
	volume or switch.
	
	When the PCM device is opened via "default" PCM (without pulse-audio
	plugin), you'll likely have "Digital Capture Volume" control as well.
	This is provided for the extra gain/attenuation of the signal in
	software, especially for the inputs without the hardware volume
	control such as digital microphones.  Unless really needed, this
	should be set to exactly 50%, corresponding to 0dB -- neither extra
	gain nor attenuation.  When you use "hw" PCM, i.e., a raw access PCM,
	this control will have no influence, though.
	
	It's known that some codecs / devices have fairly bad analog circuits,
	and the recorded sound contains a certain DC-offset.  This is no bug
	of the driver.
	
	Most of modern laptops have no analog CD-input connection.  Thus, the
	recording from CD input won't work in many cases although the driver
	provides it as the capture source.  Use CDDA instead.
	
	The automatic switching of the built-in and external mic per plugging
	is implemented on some codec models but not on every model.  Partly
	because of my laziness but mostly lack of testers.  Feel free to
	submit the improvement patch to the author.
	
	
	Direct Debugging
	~~~~~~~~~~~~~~~~
	If no model option gives you a better result, and you are a tough guy
	to fight against evil, try debugging via hitting the raw HD-audio
	codec verbs to the device.  Some tools are available: hda-emu and
	hda-analyzer.  The detailed description is found in the sections
	below.  You'd need to enable hwdep for using these tools.  See "Kernel
	Configuration" section.
	
	
	OTHER ISSUES
	------------
	
	Kernel Configuration
	~~~~~~~~~~~~~~~~~~~~
	In general, I recommend you to enable the sound debug option,
	`CONFIG_SND_DEBUG=y`, no matter whether you are debugging or not.
	This enables snd_printd() macro and others, and you'll get additional
	kernel messages at probing.
	
	In addition, you can enable `CONFIG_SND_DEBUG_VERBOSE=y`.  But this
	will give you far more messages.  Thus turn this on only when you are
	sure to want it.
	
	Don't forget to turn on the appropriate `CONFIG_SND_HDA_CODEC_*`
	options.  Note that each of them corresponds to the codec chip, not
	the controller chip.  Thus, even if lspci shows the Nvidia controller,
	you may need to choose the option for other vendors.  If you are
	unsure, just select all yes.
	
	`CONFIG_SND_HDA_HWDEP` is a useful option for debugging the driver.
	When this is enabled, the driver creates hardware-dependent devices
	(one per each codec), and you have a raw access to the device via
	these device files.  For example, `hwC0D2` will be created for the
	codec slot #2 of the first card (#0).  For debug-tools such as
	hda-verb and hda-analyzer, the hwdep device has to be enabled.
	Thus, it'd be better to turn this on always.
	
	`CONFIG_SND_HDA_RECONFIG` is a new option, and this depends on the
	hwdep option above.  When enabled, you'll have some sysfs files under
	the corresponding hwdep directory.  See "HD-audio reconfiguration"
	section below.
	
	`CONFIG_SND_HDA_POWER_SAVE` option enables the power-saving feature.
	See "Power-saving" section below.
	
	
	Codec Proc-File
	~~~~~~~~~~~~~~~
	The codec proc-file is a treasure-chest for debugging HD-audio.
	It shows most of useful information of each codec widget.
	
	The proc file is located in /proc/asound/card*/codec#*, one file per
	each codec slot.  You can know the codec vendor, product id and
	names, the type of each widget, capabilities and so on.
	This file, however, doesn't show the jack sensing state, so far.  This
	is because the jack-sensing might be depending on the trigger state.
	
	This file will be picked up by the debug tools, and also it can be fed
	to the emulator as the primary codec information.  See the debug tools
	section below.
	
	This proc file can be also used to check whether the generic parser is
	used.  When the generic parser is used, the vendor/product ID name
	will appear as "Realtek ID 0262", instead of "Realtek ALC262".
	
	
	HD-Audio Reconfiguration
	~~~~~~~~~~~~~~~~~~~~~~~~
	This is an experimental feature to allow you re-configure the HD-audio
	codec dynamically without reloading the driver.  The following sysfs
	files are available under each codec-hwdep device directory (e.g. 
	/sys/class/sound/hwC0D0):
	
	vendor_id::
	  Shows the 32bit codec vendor-id hex number.  You can change the
	  vendor-id value by writing to this file.
	subsystem_id::
	  Shows the 32bit codec subsystem-id hex number.  You can change the
	  subsystem-id value by writing to this file.
	revision_id::
	  Shows the 32bit codec revision-id hex number.  You can change the
	  revision-id value by writing to this file.
	afg::
	  Shows the AFG ID.  This is read-only.
	mfg::
	  Shows the MFG ID.  This is read-only.
	name::
	  Shows the codec name string.  Can be changed by writing to this
	  file.
	modelname::
	  Shows the currently set `model` option.  Can be changed by writing
	  to this file.
	init_verbs::
	  The extra verbs to execute at initialization.  You can add a verb by
	  writing to this file.  Pass three numbers: nid, verb and parameter
	  (separated with a space).
	hints::
	  Shows / stores hint strings for codec parsers for any use.
	  Its format is `key = value`.  For example, passing `jack_detect = no`
	  will disable the jack detection of the machine completely.
	init_pin_configs::
	  Shows the initial pin default config values set by BIOS.
	driver_pin_configs::
	  Shows the pin default values set by the codec parser explicitly.
	  This doesn't show all pin values but only the changed values by
	  the parser.  That is, if the parser doesn't change the pin default
	  config values by itself, this will contain nothing.
	user_pin_configs::
	  Shows the pin default config values to override the BIOS setup.
	  Writing this (with two numbers, NID and value) appends the new
	  value.  The given will be used instead of the initial BIOS value at
	  the next reconfiguration time.  Note that this config will override
	  even the driver pin configs, too.
	reconfig::
	  Triggers the codec re-configuration.  When any value is written to
	  this file, the driver re-initialize and parses the codec tree
	  again.  All the changes done by the sysfs entries above are taken
	  into account.
	clear::
	  Resets the codec, removes the mixer elements and PCM stuff of the
	  specified codec, and clear all init verbs and hints.
	
	For example, when you want to change the pin default configuration
	value of the pin widget 0x14 to 0x9993013f, and let the driver
	re-configure based on that state, run like below:
	------------------------------------------------------------------------
	  # echo 0x14 0x9993013f > /sys/class/sound/hwC0D0/user_pin_configs
	  # echo 1 > /sys/class/sound/hwC0D0/reconfig  
	------------------------------------------------------------------------
	
	
	Hint Strings
	~~~~~~~~~~~~
	The codec parser have several switches and adjustment knobs for
	matching better with the actual codec or device behavior.  Many of
	them can be adjusted dynamically via "hints" strings as mentioned in
	the section above.  For example, by passing `jack_detect = no` string
	via sysfs or a patch file, you can disable the jack detection, thus
	the codec parser will skip the features like auto-mute or mic
	auto-switch.  As a boolean value, either `yes`, `no`, `true`, `false`,
	`1` or `0` can be passed.
	
	The generic parser supports the following hints:
	
	- jack_detect (bool): specify whether the jack detection is available
	  at all on this machine; default true
	- inv_jack_detect (bool): indicates that the jack detection logic is
	  inverted
	- trigger_sense (bool): indicates that the jack detection needs the
	  explicit call of AC_VERB_SET_PIN_SENSE verb
	- inv_eapd (bool): indicates that the EAPD is implemented in the
	  inverted logic
	- pcm_format_first (bool): sets the PCM format before the stream tag
	  and channel ID
	- sticky_stream (bool): keep the PCM format, stream tag and ID as long
	  as possible; default true
	- spdif_status_reset (bool): reset the SPDIF status bits at each time
	  the SPDIF stream is set up
	-  pin_amp_workaround (bool): the output pin may have multiple amp
	  values
	- single_adc_amp (bool): ADCs can have only single input amps
	- auto_mute (bool): enable/disable the headphone auto-mute feature;
	  default true
	- auto_mic (bool): enable/disable the mic auto-switch feature; default
	  true
	- line_in_auto_switch (bool): enable/disable the line-in auto-switch
	  feature; default false
	- need_dac_fix (bool): limits the DACs depending on the channel count
	- primary_hp (bool): probe headphone jacks as the primary outputs;
	  default true
	- multi_cap_vol (bool): provide multiple capture volumes
	- inv_dmic_split (bool): provide split internal mic volume/switch for
	  phase-inverted digital mics
	- indep_hp (bool): provide the independent headphone PCM stream and
	  the corresponding mixer control, if available
	- add_stereo_mix_input (bool): add the stereo mix (analog-loopback
	  mix) to the input mux if available
	- add_out_jack_modes (bool): add "xxx Jack Mode" enum controls to each
	  output jack for allowing to change the headphone amp capability
	- add_in_jack_modes (bool): add "xxx Jack Mode" enum controls to each
	  input jack for allowing to change the mic bias vref
	- power_down_unused (bool): power down the unused widgets
	- mixer_nid (int): specifies the widget NID of the analog-loopback
	  mixer
	
	
	Early Patching
	~~~~~~~~~~~~~~
	When CONFIG_SND_HDA_PATCH_LOADER=y is set, you can pass a "patch" as a
	firmware file for modifying the HD-audio setup before initializing the
	codec.  This can work basically like the reconfiguration via sysfs in
	the above, but it does it before the first codec configuration.
	
	A patch file is a plain text file which looks like below:
	
	------------------------------------------------------------------------
	  [codec]
	  0x12345678 0xabcd1234 2
	
	  [model]
	  auto
	
	  [pincfg]
	  0x12 0x411111f0
	
	  [verb]
	  0x20 0x500 0x03
	  0x20 0x400 0xff
	
	  [hint]
	  jack_detect = no
	------------------------------------------------------------------------
	
	The file needs to have a line `[codec]`.  The next line should contain
	three numbers indicating the codec vendor-id (0x12345678 in the
	example), the codec subsystem-id (0xabcd1234) and the address (2) of
	the codec.  The rest patch entries are applied to this specified codec
	until another codec entry is given.  Passing 0 or a negative number to
	the first or the second value will make the check of the corresponding
	field be skipped.  It'll be useful for really broken devices that don't
	initialize SSID properly.
	
	The `[model]` line allows to change the model name of the each codec.
	In the example above, it will be changed to model=auto.
	Note that this overrides the module option.
	
	After the `[pincfg]` line, the contents are parsed as the initial
	default pin-configurations just like `user_pin_configs` sysfs above.
	The values can be shown in user_pin_configs sysfs file, too.
	
	Similarly, the lines after `[verb]` are parsed as `init_verbs`
	sysfs entries, and the lines after `[hint]` are parsed as `hints`
	sysfs entries, respectively.
	
	Another example to override the codec vendor id from 0x12345678 to
	0xdeadbeef is like below:
	------------------------------------------------------------------------
	  [codec]
	  0x12345678 0xabcd1234 2
	
	  [vendor_id]
	  0xdeadbeef
	------------------------------------------------------------------------
	
	In the similar way, you can override the codec subsystem_id via
	`[subsystem_id]`, the revision id via `[revision_id]` line.
	Also, the codec chip name can be rewritten via `[chip_name]` line.
	------------------------------------------------------------------------
	  [codec]
	  0x12345678 0xabcd1234 2
	
	  [subsystem_id]
	  0xffff1111
	
	  [revision_id]
	  0x10
	
	  [chip_name]
	  My-own NEWS-0002
	------------------------------------------------------------------------
	
	The hd-audio driver reads the file via request_firmware().  Thus,
	a patch file has to be located on the appropriate firmware path,
	typically, /lib/firmware.  For example, when you pass the option
	`patch=hda-init.fw`, the file /lib/firmware/hda-init.fw must be
	present.
	
	The patch module option is specific to each card instance, and you
	need to give one file name for each instance, separated by commas.
	For example, if you have two cards, one for an on-board analog and one 
	for an HDMI video board, you may pass patch option like below:
	------------------------------------------------------------------------
	    options snd-hda-intel patch=on-board-patch,hdmi-patch
	------------------------------------------------------------------------
	
	
	Power-Saving
	~~~~~~~~~~~~
	The power-saving is a kind of auto-suspend of the device.  When the
	device is inactive for a certain time, the device is automatically
	turned off to save the power.  The time to go down is specified via
	`power_save` module option, and this option can be changed dynamically
	via sysfs.
	
	The power-saving won't work when the analog loopback is enabled on
	some codecs.  Make sure that you mute all unneeded signal routes when
	you want the power-saving.
	
	The power-saving feature might cause audible click noises at each
	power-down/up depending on the device.  Some of them might be
	solvable, but some are hard, I'm afraid.  Some distros such as
	openSUSE enables the power-saving feature automatically when the power
	cable is unplugged.  Thus, if you hear noises, suspect first the
	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.
	
	The recent kernel supports the runtime PM for the HD-audio controller
	chip, too.  It means that the HD-audio controller is also powered up /
	down dynamically.  The feature is enabled only for certain controller
	chips like Intel LynxPoint.  You can enable/disable this feature
	forcibly by setting `power_save_controller` option, which is also
	available at /sys/module/snd_hda_intel/parameters directory.
	
	
	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,
	`hda:hda_unsol_event` traces the unsolicited events, 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:
	
	- git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git
	
	The master branch or for-next branches can be used as the main
	development branches in general while the development for the current
	and next kernels are found in for-linus and for-next branches,
	respectively.
	
	If you are using the latest Linus tree, it'd be better to pull the
	above GIT tree onto it.  If you are using the older kernels, an easy
	way to try the latest ALSA code is to build from the snapshot
	tarball.  There are daily tarballs and the latest snapshot tarball.
	All can be built just like normal alsa-driver release packages, that
	is, installed via the usual spells: configure, make and make
	install(-modules).  See INSTALL in the package.  The snapshot tarballs
	are found at:
	
	- ftp://ftp.suse.com/pub/people/tiwai/snapshot/
	
	
	Sending a Bug Report
	~~~~~~~~~~~~~~~~~~~~
	If any model or module options don't work for your device, it's time
	to send a bug report to the developers.  Give the following in your
	bug report:
	
	- Hardware vendor, product and model names
	- Kernel version (and ALSA-driver version if you built externally)
	- `alsa-info.sh` output; run with `--no-upload` option.  See the
	  section below about alsa-info
	
	If it's a regression, at best, send alsa-info outputs of both working
	and non-working kernels.  This is really helpful because we can
	compare the codec registers directly.
	
	Send a bug report either the followings:
	
	kernel-bugzilla::
	  https://bugzilla.kernel.org/
	alsa-devel ML::
	  alsa-devel@alsa-project.org
	
	
	DEBUG TOOLS
	-----------
	
	This section describes some tools available for debugging HD-audio
	problems.
	
	alsa-info
	~~~~~~~~~
	The script `alsa-info.sh` is a very useful tool to gather the audio
	device information.  You can fetch the latest version from:
	
	- http://www.alsa-project.org/alsa-info.sh
	
	Run this script as root, and it will gather the important information
	such as the module lists, module parameters, proc file contents
	including the codec proc files, mixer outputs and the control
	elements.  As default, it will store the information onto a web server
	on alsa-project.org.  But, if you send a bug report, it'd be better to
	run with `--no-upload` option, and attach the generated file.
	
	There are some other useful options.  See `--help` option output for
	details.
	
	When a probe error occurs or when the driver obviously assigns a
	mismatched model, it'd be helpful to load the driver with
	`probe_only=1` option (at best after the cold reboot) and run
	alsa-info at this state.  With this option, the driver won't configure
	the mixer and PCM but just tries to probe the codec slot.  After
	probing, the proc file is available, so you can get the raw codec
	information before modified by the driver.  Of course, the driver
	isn't usable with `probe_only=1`.  But you can continue the
	configuration via hwdep sysfs file if hda-reconfig option is enabled.
	Using `probe_only` mask 2 skips the reset of HDA codecs (use
	`probe_only=3` as module option). The hwdep interface can be used
	to determine the BIOS codec initialization.
	
	
	hda-verb
	~~~~~~~~
	hda-verb is a tiny program that allows you to access the HD-audio
	codec directly.  You can execute a raw HD-audio codec verb with this.
	This program accesses the hwdep device, thus you need to enable the
	kernel config `CONFIG_SND_HDA_HWDEP=y` beforehand.
	
	The hda-verb program takes four arguments: the hwdep device file, the
	widget NID, the verb and the parameter.  When you access to the codec
	on the slot 2 of the card 0, pass /dev/snd/hwC0D2 to the first
	argument, typically.  (However, the real path name depends on the
	system.)
	
	The second parameter is the widget number-id to access.  The third
	parameter can be either a hex/digit number or a string corresponding
	to a verb.  Similarly, the last parameter is the value to write, or
	can be a string for the parameter type.
	
	------------------------------------------------------------------------
	  % hda-verb /dev/snd/hwC0D0 0x12 0x701 2
	  nid = 0x12, verb = 0x701, param = 0x2
	  value = 0x0
	
	  % hda-verb /dev/snd/hwC0D0 0x0 PARAMETERS VENDOR_ID
	  nid = 0x0, verb = 0xf00, param = 0x0
	  value = 0x10ec0262
	
	  % hda-verb /dev/snd/hwC0D0 2 set_a 0xb080
	  nid = 0x2, verb = 0x300, param = 0xb080
	  value = 0x0
	------------------------------------------------------------------------
	
	Although you can issue any verbs with this program, the driver state
	won't be always updated.  For example, the volume values are usually
	cached in the driver, and thus changing the widget amp value directly
	via hda-verb won't change the mixer value.
	
	The hda-verb program is included now in alsa-tools:
	
	- git://git.alsa-project.org/alsa-tools.git
	
	Also, the old stand-alone package is found in the ftp directory:
	
	- ftp://ftp.suse.com/pub/people/tiwai/misc/
	
	Also a git repository is available:
	
	- git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/hda-verb.git
	
	See README file in the tarball for more details about hda-verb
	program.
	
	
	hda-analyzer
	~~~~~~~~~~~~
	hda-analyzer provides a graphical interface to access the raw HD-audio
	control, based on pyGTK2 binding.  It's a more powerful version of
	hda-verb.  The program gives you an easy-to-use GUI stuff for showing
	the widget information and adjusting the amp values, as well as the
	proc-compatible output.
	
	The hda-analyzer:
	
	- http://git.alsa-project.org/?p=alsa.git;a=tree;f=hda-analyzer
	
	is a part of alsa.git repository in alsa-project.org:
	
	- git://git.alsa-project.org/alsa.git
	
	Codecgraph
	~~~~~~~~~~
	Codecgraph is a utility program to generate a graph and visualizes the
	codec-node connection of a codec chip.  It's especially useful when
	you analyze or debug a codec without a proper datasheet.  The program
	parses the given codec proc file and converts to SVG via graphiz
	program.
	
	The tarball and GIT trees are found in the web page at:
	
	- http://helllabs.org/codecgraph/
	
	
	hda-emu
	~~~~~~~
	hda-emu is an HD-audio emulator.  The main purpose of this program is
	to debug an HD-audio codec without the real hardware.  Thus, it
	doesn't emulate the behavior with the real audio I/O, but it just
	dumps the codec register changes and the ALSA-driver internal changes
	at probing and operating the HD-audio driver.
	
	The program requires a codec proc-file to simulate.  Get a proc file
	for the target codec beforehand, or pick up an example codec from the
	codec proc collections in the tarball.  Then, run the program with the
	proc file, and the hda-emu program will start parsing the codec file
	and simulates the HD-audio driver:
	
	------------------------------------------------------------------------
	  % hda-emu codecs/stac9200-dell-d820-laptop
	  # Parsing..
	  hda_codec: Unknown model for STAC9200, using BIOS defaults
	  hda_codec: pin nid 08 bios pin config 40c003fa
	  ....
	------------------------------------------------------------------------
	
	The program gives you only a very dumb command-line interface.  You
	can get a proc-file dump at the current state, get a list of control
	(mixer) elements, set/get the control element value, simulate the PCM
	operation, the jack plugging simulation, etc.
	
	The package is found in:
	
	- ftp://ftp.suse.com/pub/people/tiwai/misc/
	
	A git repository is available:
	
	- git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/hda-emu.git
	
	See README file in the tarball for more details about hda-emu
	program.
	
	
	hda-jack-retask
	~~~~~~~~~~~~~~~
	hda-jack-retask is a user-friendly GUI program to manipulate the
	HD-audio pin control for jack retasking.  If you have a problem about
	the jack assignment, try this program and check whether you can get
	useful results.  Once when you figure out the proper pin assignment,
	it can be fixed either in the driver code statically or via passing a
	firmware patch file (see "Early Patching" section).
	
	The program is included in alsa-tools now:
	
	- git://git.alsa-project.org/alsa-tools.git

• [ alsa ]
• ALSA-Configuration.txt
• alsa-parameters.txt
• Audigy-mixer.txt
• Audiophile-Usb.txt
• Bt87x.txt
• Channel-Mapping-API.txt
• CMIPCI.txt
• compress_offload.txt
• ControlNames.txt
• emu10k1-jack.txt
• HD-Audio-Controls.txt
• HD-Audio-Models.txt
• HD-Audio.txt
• hda_codec.txt
• hdspm.txt
• Joystick.txt
• MIXART.txt
• OSS-Emulation.txt
• powersave.txt
• Procfile.txt
• README.maya44
• SB-Live-mixer.txt
• seq_oss.html
• serial-u16550.txt
• [ soc ]
• VIA82xx-mixer.txt
•