Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

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+=============================
+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:
+
+* https://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.
+``position_fix=5`` is specific to Intel platforms, so far, for Skylake
+and onward.  It applies the delay calculation for the precise position
+reporting.
+``position_fix=6`` is to correct the position with the fixed FIFO
+size, mainly targeted for the recent AMD controllers.
+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/hd-audio/models.rst 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_io (bool)
+    try probing multi-I/O config (e.g. shared line-in/surround,
+    mic/clfe jacks)
+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_jack_modes (bool)
+    add "xxx Jack Mode" enum controls to each I/O jack for allowing to
+    change the headphone amp and mic bias VREF capabilities
+power_save_node (bool)
+    advanced power management for each widget, controlling the power
+    sate (D0/D3) of each widget node depending on the actual pin and
+    stream states
+power_down_unused (bool)
+    power down the unused widgets, a subset of power_save_node, and
+    will be dropped in future 
+add_hp_mic (bool)
+    add the headphone to capture source if possible
+hp_mic_detect (bool)
+    enable/disable the hp/mic shared input for a single built-in mic
+    case; default true
+vmaster (bool)
+    enable/disable the virtual Master control; default true
+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.
+
+
+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 following:
+
+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.  It's included in alsa-utils package.  The latest
+version can be found on git repository:
+
+* git://git.alsa-project.org/alsa-utils.git
+
+The script can be fetched directly from the following URL, too:
+
+* https://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:
+
+* https://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 program is found in the git repository below:
+
+* git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/hda-emu.git
+
+See README file in the repository 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