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Based on kernel version 3.2. Page generated on 2012-01-05 23:29 EST.

1	MORE NOTES ON HD-AUDIO DRIVER
2	=============================
3						Takashi Iwai <tiwai@suse.de>
4	
5	
6	GENERAL
7	-------
8	
9	HD-audio is the new standard on-board audio component on modern PCs
10	after AC97.  Although Linux has been supporting HD-audio since long
11	time ago, there are often problems with new machines.  A part of the
12	problem is broken BIOS, and the rest is the driver implementation.
13	This document explains the brief trouble-shooting and debugging
14	methods for the	HD-audio hardware.
15	
16	The HD-audio component consists of two parts: the controller chip and 
17	the codec chips on the HD-audio bus.  Linux provides a single driver
18	for all controllers, snd-hda-intel.  Although the driver name contains
19	a word of a well-known hardware vendor, it's not specific to it but for
20	all controller chips by other companies.  Since the HD-audio
21	controllers are supposed to be compatible, the single snd-hda-driver
22	should work in most cases.  But, not surprisingly, there are known
23	bugs and issues specific to each controller type.  The snd-hda-intel
24	driver has a bunch of workarounds for these as described below.
25	
26	A controller may have multiple codecs.  Usually you have one audio
27	codec and optionally one modem codec.  In theory, there might be
28	multiple audio codecs, e.g. for analog and digital outputs, and the
29	driver might not work properly because of conflict of mixer elements.
30	This should be fixed in future if such hardware really exists.
31	
32	The snd-hda-intel driver has several different codec parsers depending
33	on the codec.  It has a generic parser as a fallback, but this
34	functionality is fairly limited until now.  Instead of the generic
35	parser, usually the codec-specific parser (coded in patch_*.c) is used
36	for the codec-specific implementations.  The details about the
37	codec-specific problems are explained in the later sections.
38	
39	If you are interested in the deep debugging of HD-audio, read the
40	HD-audio specification at first.  The specification is found on
41	Intel's web page, for example:
42	
43	- http://www.intel.com/standards/hdaudio/
44	
45	
46	HD-AUDIO CONTROLLER
47	-------------------
48	
49	DMA-Position Problem
50	~~~~~~~~~~~~~~~~~~~~
51	The most common problem of the controller is the inaccurate DMA
52	pointer reporting.  The DMA pointer for playback and capture can be
53	read in two ways, either via a LPIB register or via a position-buffer
54	map.  As default the driver tries to read from the io-mapped
55	position-buffer, and falls back to LPIB if the position-buffer appears
56	dead.  However, this detection isn't perfect on some devices.  In such
57	a case, you can change the default method via `position_fix` option.
58	
59	`position_fix=1` means to use LPIB method explicitly.
60	`position_fix=2` means to use the position-buffer.
61	`position_fix=3` means to use a combination of both methods, needed
62	for some VIA and ATI controllers.  0 is the default value for all other
63	controllers, the automatic check and fallback to LPIB as described in
64	the above.  If you get a problem of repeated sounds, this option might
65	help.
66	
67	In addition to that, every controller is known to be broken regarding
68	the wake-up timing.  It wakes up a few samples before actually
69	processing the data on the buffer.  This caused a lot of problems, for
70	example, with ALSA dmix or JACK.  Since 2.6.27 kernel, the driver puts
71	an artificial delay to the wake up timing.  This delay is controlled
72	via `bdl_pos_adj` option. 
73	
74	When `bdl_pos_adj` is a negative value (as default), it's assigned to
75	an appropriate value depending on the controller chip.  For Intel
76	chips, it'd be 1 while it'd be 32 for others.  Usually this works.
77	Only in case it doesn't work and you get warning messages, you should
78	change this parameter to other values.
79	
80	
81	Codec-Probing Problem
82	~~~~~~~~~~~~~~~~~~~~~
83	A less often but a more severe problem is the codec probing.  When
84	BIOS reports the available codec slots wrongly, the driver gets
85	confused and tries to access the non-existing codec slot.  This often
86	results in the total screw-up, and destructs the further communication
87	with the codec chips.  The symptom appears usually as error messages
88	like:
89	------------------------------------------------------------------------
90	  hda_intel: azx_get_response timeout, switching to polling mode:
91	        last cmd=0x12345678
92	  hda_intel: azx_get_response timeout, switching to single_cmd mode:
93	        last cmd=0x12345678
94	------------------------------------------------------------------------
95	
96	The first line is a warning, and this is usually relatively harmless.
97	It means that the codec response isn't notified via an IRQ.  The
98	driver uses explicit polling method to read the response.  It gives
99	very slight CPU overhead, but you'd unlikely notice it.
100	
101	The second line is, however, a fatal error.  If this happens, usually
102	it means that something is really wrong.  Most likely you are
103	accessing a non-existing codec slot.
104	
105	Thus, if the second error message appears, try to narrow the probed
106	codec slots via `probe_mask` option.  It's a bitmask, and each bit
107	corresponds to the codec slot.  For example, to probe only the first
108	slot, pass `probe_mask=1`.  For the first and the third slots, pass
109	`probe_mask=5` (where 5 = 1 | 4), and so on.
110	
111	Since 2.6.29 kernel, the driver has a more robust probing method, so
112	this error might happen rarely, though.
113	
114	On a machine with a broken BIOS, sometimes you need to force the
115	driver to probe the codec slots the hardware doesn't report for use.
116	In such a case, turn the bit 8 (0x100) of `probe_mask` option on.
117	Then the rest 8 bits are passed as the codec slots to probe
118	unconditionally.  For example, `probe_mask=0x103` will force to probe
119	the codec slots 0 and 1 no matter what the hardware reports.
120	
121	
122	Interrupt Handling
123	~~~~~~~~~~~~~~~~~~
124	HD-audio driver uses MSI as default (if available) since 2.6.33
125	kernel as MSI works better on some machines, and in general, it's
126	better for performance.  However, Nvidia controllers showed bad
127	regressions with MSI (especially in a combination with AMD chipset),
128	thus we disabled MSI for them.
129	
130	There seem also still other devices that don't work with MSI.  If you
131	see a regression wrt the sound quality (stuttering, etc) or a lock-up
132	in the recent kernel, try to pass `enable_msi=0` option to disable
133	MSI.  If it works, you can add the known bad device to the blacklist
134	defined in hda_intel.c.  In such a case, please report and give the
135	patch back to the upstream developer. 
136	
137	
138	HD-AUDIO CODEC
139	--------------
140	
141	Model Option
142	~~~~~~~~~~~~
143	The most common problem regarding the HD-audio driver is the
144	unsupported codec features or the mismatched device configuration.
145	Most of codec-specific code has several preset models, either to
146	override the BIOS setup or to provide more comprehensive features.
147	
148	The driver checks PCI SSID and looks through the static configuration
149	table until any matching entry is found.  If you have a new machine,
150	you may see a message like below:
151	------------------------------------------------------------------------
152	    hda_codec: ALC880: BIOS auto-probing.
153	------------------------------------------------------------------------
154	Meanwhile, in the earlier versions, you would see a message like:
155	------------------------------------------------------------------------
156	    hda_codec: Unknown model for ALC880, trying auto-probe from BIOS...
157	------------------------------------------------------------------------
158	Even if you see such a message, DON'T PANIC.  Take a deep breath and
159	keep your towel.  First of all, it's an informational message, no
160	warning, no error.  This means that the PCI SSID of your device isn't
161	listed in the known preset model (white-)list.  But, this doesn't mean
162	that the driver is broken.  Many codec-drivers provide the automatic
163	configuration mechanism based on the BIOS setup.
164	
165	The HD-audio codec has usually "pin" widgets, and BIOS sets the default
166	configuration of each pin, which indicates the location, the
167	connection type, the jack color, etc.  The HD-audio driver can guess
168	the right connection judging from these default configuration values.
169	However -- some codec-support codes, such as patch_analog.c, don't
170	support the automatic probing (yet as of 2.6.28).  And, BIOS is often,
171	yes, pretty often broken.  It sets up wrong values and screws up the
172	driver.
173	
174	The preset model is provided basically to overcome such a situation.
175	When the matching preset model is found in the white-list, the driver
176	assumes the static configuration of that preset and builds the mixer
177	elements and PCM streams based on the static information.  Thus, if
178	you have a newer machine with a slightly different PCI SSID from the
179	existing one, you may have a good chance to re-use the same model.
180	You can pass the `model` option to specify the preset model instead of
181	PCI SSID look-up.
182	
183	What `model` option values are available depends on the codec chip.
184	Check your codec chip from the codec proc file (see "Codec Proc-File"
185	section below).  It will show the vendor/product name of your codec
186	chip.  Then, see Documentation/sound/alsa/HD-Audio-Models.txt file,
187	the section of HD-audio driver.  You can find a list of codecs
188	and `model` options belonging to each codec.  For example, for Realtek
189	ALC262 codec chip, pass `model=ultra` for devices that are compatible
190	with Samsung Q1 Ultra.
191	
192	Thus, the first thing you can do for any brand-new, unsupported and
193	non-working HD-audio hardware is to check HD-audio codec and several
194	different `model` option values.  If you have any luck, some of them
195	might suit with your device well.
196	
197	Some codecs such as ALC880 have a special model option `model=test`.
198	This configures the driver to provide as many mixer controls as
199	possible for every single pin feature except for the unsolicited
200	events (and maybe some other specials).  Adjust each mixer element and
201	try the I/O in the way of trial-and-error until figuring out the whole
202	I/O pin mappings.
203	
204	Note that `model=generic` has a special meaning.  It means to use the
205	generic parser regardless of the codec.  Usually the codec-specific
206	parser is much better than the generic parser (as now).  Thus this
207	option is more about the debugging purpose.
208	
209	Speaker and Headphone Output
210	~~~~~~~~~~~~~~~~~~~~~~~~~~~~
211	One of the most frequent (and obvious) bugs with HD-audio is the
212	silent output from either or both of a built-in speaker and a
213	headphone jack.  In general, you should try a headphone output at
214	first.  A speaker output often requires more additional controls like
215	the external amplifier bits.  Thus a headphone output has a slightly
216	better chance.
217	
218	Before making a bug report, double-check whether the mixer is set up
219	correctly.  The recent version of snd-hda-intel driver provides mostly
220	"Master" volume control as well as "Front" volume (where Front
221	indicates the front-channels).  In addition, there can be individual
222	"Headphone" and "Speaker" controls.
223	
224	Ditto for the speaker output.  There can be "External Amplifier"
225	switch on some codecs.  Turn on this if present.
226	
227	Another related problem is the automatic mute of speaker output by
228	headphone plugging.  This feature is implemented in most cases, but
229	not on every preset model or codec-support code.
230	
231	In anyway, try a different model option if you have such a problem.
232	Some other models may match better and give you more matching
233	functionality.  If none of the available models works, send a bug
234	report.  See the bug report section for details.
235	
236	If you are masochistic enough to debug the driver problem, note the
237	following:
238	
239	- The speaker (and the headphone, too) output often requires the
240	  external amplifier.  This can be set usually via EAPD verb or a
241	  certain GPIO.  If the codec pin supports EAPD, you have a better
242	  chance via SET_EAPD_BTL verb (0x70c).  On others, GPIO pin (mostly
243	  it's either GPIO0 or GPIO1) may turn on/off EAPD.
244	- Some Realtek codecs require special vendor-specific coefficients to
245	  turn on the amplifier.  See patch_realtek.c.
246	- IDT codecs may have extra power-enable/disable controls on each
247	  analog pin.  See patch_sigmatel.c.
248	- Very rare but some devices don't accept the pin-detection verb until
249	  triggered.  Issuing GET_PIN_SENSE verb (0xf09) may result in the
250	  codec-communication stall.  Some examples are found in
251	  patch_realtek.c.
252	
253	
254	Capture Problems
255	~~~~~~~~~~~~~~~~
256	The capture problems are often because of missing setups of mixers.
257	Thus, before submitting a bug report, make sure that you set up the
258	mixer correctly.  For example, both "Capture Volume" and "Capture
259	Switch" have to be set properly in addition to the right "Capture
260	Source" or "Input Source" selection.  Some devices have "Mic Boost"
261	volume or switch.
262	
263	When the PCM device is opened via "default" PCM (without pulse-audio
264	plugin), you'll likely have "Digital Capture Volume" control as well.
265	This is provided for the extra gain/attenuation of the signal in
266	software, especially for the inputs without the hardware volume
267	control such as digital microphones.  Unless really needed, this
268	should be set to exactly 50%, corresponding to 0dB -- neither extra
269	gain nor attenuation.  When you use "hw" PCM, i.e., a raw access PCM,
270	this control will have no influence, though.
271	
272	It's known that some codecs / devices have fairly bad analog circuits,
273	and the recorded sound contains a certain DC-offset.  This is no bug
274	of the driver.
275	
276	Most of modern laptops have no analog CD-input connection.  Thus, the
277	recording from CD input won't work in many cases although the driver
278	provides it as the capture source.  Use CDDA instead.
279	
280	The automatic switching of the built-in and external mic per plugging
281	is implemented on some codec models but not on every model.  Partly
282	because of my laziness but mostly lack of testers.  Feel free to
283	submit the improvement patch to the author.
284	
285	
286	Direct Debugging
287	~~~~~~~~~~~~~~~~
288	If no model option gives you a better result, and you are a tough guy
289	to fight against evil, try debugging via hitting the raw HD-audio
290	codec verbs to the device.  Some tools are available: hda-emu and
291	hda-analyzer.  The detailed description is found in the sections
292	below.  You'd need to enable hwdep for using these tools.  See "Kernel
293	Configuration" section.
294	
295	
296	OTHER ISSUES
297	------------
298	
299	Kernel Configuration
300	~~~~~~~~~~~~~~~~~~~~
301	In general, I recommend you to enable the sound debug option,
302	`CONFIG_SND_DEBUG=y`, no matter whether you are debugging or not.
303	This enables snd_printd() macro and others, and you'll get additional
304	kernel messages at probing.
305	
306	In addition, you can enable `CONFIG_SND_DEBUG_VERBOSE=y`.  But this
307	will give you far more messages.  Thus turn this on only when you are
308	sure to want it.
309	
310	Don't forget to turn on the appropriate `CONFIG_SND_HDA_CODEC_*`
311	options.  Note that each of them corresponds to the codec chip, not
312	the controller chip.  Thus, even if lspci shows the Nvidia controller,
313	you may need to choose the option for other vendors.  If you are
314	unsure, just select all yes.
315	
316	`CONFIG_SND_HDA_HWDEP` is a useful option for debugging the driver.
317	When this is enabled, the driver creates hardware-dependent devices
318	(one per each codec), and you have a raw access to the device via
319	these device files.  For example, `hwC0D2` will be created for the
320	codec slot #2 of the first card (#0).  For debug-tools such as
321	hda-verb and hda-analyzer, the hwdep device has to be enabled.
322	Thus, it'd be better to turn this on always.
323	
324	`CONFIG_SND_HDA_RECONFIG` is a new option, and this depends on the
325	hwdep option above.  When enabled, you'll have some sysfs files under
326	the corresponding hwdep directory.  See "HD-audio reconfiguration"
327	section below.
328	
329	`CONFIG_SND_HDA_POWER_SAVE` option enables the power-saving feature.
330	See "Power-saving" section below.
331	
332	
333	Codec Proc-File
334	~~~~~~~~~~~~~~~
335	The codec proc-file is a treasure-chest for debugging HD-audio.
336	It shows most of useful information of each codec widget.
337	
338	The proc file is located in /proc/asound/card*/codec#*, one file per
339	each codec slot.  You can know the codec vendor, product id and
340	names, the type of each widget, capabilities and so on.
341	This file, however, doesn't show the jack sensing state, so far.  This
342	is because the jack-sensing might be depending on the trigger state.
343	
344	This file will be picked up by the debug tools, and also it can be fed
345	to the emulator as the primary codec information.  See the debug tools
346	section below.
347	
348	This proc file can be also used to check whether the generic parser is
349	used.  When the generic parser is used, the vendor/product ID name
350	will appear as "Realtek ID 0262", instead of "Realtek ALC262".
351	
352	
353	HD-Audio Reconfiguration
354	~~~~~~~~~~~~~~~~~~~~~~~~
355	This is an experimental feature to allow you re-configure the HD-audio
356	codec dynamically without reloading the driver.  The following sysfs
357	files are available under each codec-hwdep device directory (e.g. 
358	/sys/class/sound/hwC0D0):
359	
360	vendor_id::
361	  Shows the 32bit codec vendor-id hex number.  You can change the
362	  vendor-id value by writing to this file.
363	subsystem_id::
364	  Shows the 32bit codec subsystem-id hex number.  You can change the
365	  subsystem-id value by writing to this file.
366	revision_id::
367	  Shows the 32bit codec revision-id hex number.  You can change the
368	  revision-id value by writing to this file.
369	afg::
370	  Shows the AFG ID.  This is read-only.
371	mfg::
372	  Shows the MFG ID.  This is read-only.
373	name::
374	  Shows the codec name string.  Can be changed by writing to this
375	  file.
376	modelname::
377	  Shows the currently set `model` option.  Can be changed by writing
378	  to this file.
379	init_verbs::
380	  The extra verbs to execute at initialization.  You can add a verb by
381	  writing to this file.  Pass three numbers: nid, verb and parameter
382	  (separated with a space).
383	hints::
384	  Shows / stores hint strings for codec parsers for any use.
385	  Its format is `key = value`.  For example, passing `hp_detect = yes`
386	  to IDT/STAC codec parser will result in the disablement of the
387	  headphone detection.
388	init_pin_configs::
389	  Shows the initial pin default config values set by BIOS.
390	driver_pin_configs::
391	  Shows the pin default values set by the codec parser explicitly.
392	  This doesn't show all pin values but only the changed values by
393	  the parser.  That is, if the parser doesn't change the pin default
394	  config values by itself, this will contain nothing.
395	user_pin_configs::
396	  Shows the pin default config values to override the BIOS setup.
397	  Writing this (with two numbers, NID and value) appends the new
398	  value.  The given will be used instead of the initial BIOS value at
399	  the next reconfiguration time.  Note that this config will override
400	  even the driver pin configs, too.
401	reconfig::
402	  Triggers the codec re-configuration.  When any value is written to
403	  this file, the driver re-initialize and parses the codec tree
404	  again.  All the changes done by the sysfs entries above are taken
405	  into account.
406	clear::
407	  Resets the codec, removes the mixer elements and PCM stuff of the
408	  specified codec, and clear all init verbs and hints.
409	
410	For example, when you want to change the pin default configuration
411	value of the pin widget 0x14 to 0x9993013f, and let the driver
412	re-configure based on that state, run like below:
413	------------------------------------------------------------------------
414	  # echo 0x14 0x9993013f > /sys/class/sound/hwC0D0/user_pin_configs
415	  # echo 1 > /sys/class/sound/hwC0D0/reconfig  
416	------------------------------------------------------------------------
417	
418	
419	Early Patching
420	~~~~~~~~~~~~~~
421	When CONFIG_SND_HDA_PATCH_LOADER=y is set, you can pass a "patch" as a
422	firmware file for modifying the HD-audio setup before initializing the
423	codec.  This can work basically like the reconfiguration via sysfs in
424	the above, but it does it before the first codec configuration.
425	
426	A patch file is a plain text file which looks like below:
427	
428	------------------------------------------------------------------------
429	  [codec]
430	  0x12345678 0xabcd1234 2
431	
432	  [model]
433	  auto
434	
435	  [pincfg]
436	  0x12 0x411111f0
437	
438	  [verb]
439	  0x20 0x500 0x03
440	  0x20 0x400 0xff
441	
442	  [hint]
443	  hp_detect = yes
444	------------------------------------------------------------------------
445	
446	The file needs to have a line `[codec]`.  The next line should contain
447	three numbers indicating the codec vendor-id (0x12345678 in the
448	example), the codec subsystem-id (0xabcd1234) and the address (2) of
449	the codec.  The rest patch entries are applied to this specified codec
450	until another codec entry is given.  Passing 0 or a negative number to
451	the first or the second value will make the check of the corresponding
452	field be skipped.  It'll be useful for really broken devices that don't
453	initialize SSID properly.
454	
455	The `[model]` line allows to change the model name of the each codec.
456	In the example above, it will be changed to model=auto.
457	Note that this overrides the module option.
458	
459	After the `[pincfg]` line, the contents are parsed as the initial
460	default pin-configurations just like `user_pin_configs` sysfs above.
461	The values can be shown in user_pin_configs sysfs file, too.
462	
463	Similarly, the lines after `[verb]` are parsed as `init_verbs`
464	sysfs entries, and the lines after `[hint]` are parsed as `hints`
465	sysfs entries, respectively.
466	
467	Another example to override the codec vendor id from 0x12345678 to
468	0xdeadbeef is like below:
469	------------------------------------------------------------------------
470	  [codec]
471	  0x12345678 0xabcd1234 2
472	
473	  [vendor_id]
474	  0xdeadbeef
475	------------------------------------------------------------------------
476	
477	In the similar way, you can override the codec subsystem_id via
478	`[subsystem_id]`, the revision id via `[revision_id]` line.
479	Also, the codec chip name can be rewritten via `[chip_name]` line.
480	------------------------------------------------------------------------
481	  [codec]
482	  0x12345678 0xabcd1234 2
483	
484	  [subsystem_id]
485	  0xffff1111
486	
487	  [revision_id]
488	  0x10
489	
490	  [chip_name]
491	  My-own NEWS-0002
492	------------------------------------------------------------------------
493	
494	The hd-audio driver reads the file via request_firmware().  Thus,
495	a patch file has to be located on the appropriate firmware path,
496	typically, /lib/firmware.  For example, when you pass the option
497	`patch=hda-init.fw`, the file /lib/firmware/hda-init.fw must be
498	present.
499	
500	The patch module option is specific to each card instance, and you
501	need to give one file name for each instance, separated by commas.
502	For example, if you have two cards, one for an on-board analog and one 
503	for an HDMI video board, you may pass patch option like below:
504	------------------------------------------------------------------------
505	    options snd-hda-intel patch=on-board-patch,hdmi-patch
506	------------------------------------------------------------------------
507	
508	
509	Power-Saving
510	~~~~~~~~~~~~
511	The power-saving is a kind of auto-suspend of the device.  When the
512	device is inactive for a certain time, the device is automatically
513	turned off to save the power.  The time to go down is specified via
514	`power_save` module option, and this option can be changed dynamically
515	via sysfs.
516	
517	The power-saving won't work when the analog loopback is enabled on
518	some codecs.  Make sure that you mute all unneeded signal routes when
519	you want the power-saving.
520	
521	The power-saving feature might cause audible click noises at each
522	power-down/up depending on the device.  Some of them might be
523	solvable, but some are hard, I'm afraid.  Some distros such as
524	openSUSE enables the power-saving feature automatically when the power
525	cable is unplugged.  Thus, if you hear noises, suspect first the
526	power-saving.  See /sys/module/snd_hda_intel/parameters/power_save to
527	check the current value.  If it's non-zero, the feature is turned on.
528	
529	
530	Tracepoints
531	~~~~~~~~~~~
532	The hd-audio driver gives a few basic tracepoints.
533	`hda:hda_send_cmd` traces each CORB write while `hda:hda_get_response`
534	traces the response from RIRB (only when read from the codec driver).
535	`hda:hda_bus_reset` traces the bus-reset due to fatal error, etc,
536	`hda:hda_unsol_event` traces the unsolicited events, and
537	`hda:hda_power_down` and `hda:hda_power_up` trace the power down/up
538	via power-saving behavior.
539	
540	Enabling all tracepoints can be done like
541	------------------------------------------------------------------------
542	  # echo 1 > /sys/kernel/debug/tracing/events/hda/enable
543	------------------------------------------------------------------------
544	then after some commands, you can traces from
545	/sys/kernel/debug/tracing/trace file.  For example, when you want to
546	trace what codec command is sent, enable the tracepoint like:
547	------------------------------------------------------------------------
548	  # cat /sys/kernel/debug/tracing/trace
549	  # tracer: nop
550	  #
551	  #       TASK-PID    CPU#    TIMESTAMP  FUNCTION
552	  #          | |       |          |         |
553	         <...>-7807  [002] 105147.774889: hda_send_cmd: [0:0] val=e3a019
554	         <...>-7807  [002] 105147.774893: hda_send_cmd: [0:0] val=e39019
555	         <...>-7807  [002] 105147.999542: hda_send_cmd: [0:0] val=e3a01a
556	         <...>-7807  [002] 105147.999543: hda_send_cmd: [0:0] val=e3901a
557	         <...>-26764 [001] 349222.837143: hda_send_cmd: [0:0] val=e3a019
558	         <...>-26764 [001] 349222.837148: hda_send_cmd: [0:0] val=e39019
559	         <...>-26764 [001] 349223.058539: hda_send_cmd: [0:0] val=e3a01a
560	         <...>-26764 [001] 349223.058541: hda_send_cmd: [0:0] val=e3901a
561	------------------------------------------------------------------------
562	Here `[0:0]` indicates the card number and the codec address, and
563	`val` shows the value sent to the codec, respectively.  The value is
564	a packed value, and you can decode it via hda-decode-verb program
565	included in hda-emu package below.  For example, the value e3a019 is
566	to set the left output-amp value to 25.
567	------------------------------------------------------------------------
568	  % hda-decode-verb 0xe3a019
569	  raw value = 0x00e3a019
570	  cid = 0, nid = 0x0e, verb = 0x3a0, parm = 0x19
571	  raw value: verb = 0x3a0, parm = 0x19
572	  verbname = set_amp_gain_mute
573	  amp raw val = 0xa019
574	  output, left, idx=0, mute=0, val=25
575	------------------------------------------------------------------------
576	
577	
578	Development Tree
579	~~~~~~~~~~~~~~~~
580	The latest development codes for HD-audio are found on sound git tree:
581	
582	- git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git
583	
584	The master branch or for-next branches can be used as the main
585	development branches in general while the HD-audio specific patches
586	are committed in topic/hda branch.
587	
588	If you are using the latest Linus tree, it'd be better to pull the
589	above GIT tree onto it.  If you are using the older kernels, an easy
590	way to try the latest ALSA code is to build from the snapshot
591	tarball.  There are daily tarballs and the latest snapshot tarball.
592	All can be built just like normal alsa-driver release packages, that
593	is, installed via the usual spells: configure, make and make
594	install(-modules).  See INSTALL in the package.  The snapshot tarballs
595	are found at:
596	
597	- ftp://ftp.suse.com/pub/people/tiwai/snapshot/
598	
599	
600	Sending a Bug Report
601	~~~~~~~~~~~~~~~~~~~~
602	If any model or module options don't work for your device, it's time
603	to send a bug report to the developers.  Give the following in your
604	bug report:
605	
606	- Hardware vendor, product and model names
607	- Kernel version (and ALSA-driver version if you built externally)
608	- `alsa-info.sh` output; run with `--no-upload` option.  See the
609	  section below about alsa-info
610	
611	If it's a regression, at best, send alsa-info outputs of both working
612	and non-working kernels.  This is really helpful because we can
613	compare the codec registers directly.
614	
615	Send a bug report either the followings:
616	
617	kernel-bugzilla::
618	  https://bugzilla.kernel.org/
619	alsa-devel ML::
620	  alsa-devel@alsa-project.org
621	
622	
623	DEBUG TOOLS
624	-----------
625	
626	This section describes some tools available for debugging HD-audio
627	problems.
628	
629	alsa-info
630	~~~~~~~~~
631	The script `alsa-info.sh` is a very useful tool to gather the audio
632	device information.  You can fetch the latest version from:
633	
634	- http://www.alsa-project.org/alsa-info.sh
635	
636	Run this script as root, and it will gather the important information
637	such as the module lists, module parameters, proc file contents
638	including the codec proc files, mixer outputs and the control
639	elements.  As default, it will store the information onto a web server
640	on alsa-project.org.  But, if you send a bug report, it'd be better to
641	run with `--no-upload` option, and attach the generated file.
642	
643	There are some other useful options.  See `--help` option output for
644	details.
645	
646	When a probe error occurs or when the driver obviously assigns a
647	mismatched model, it'd be helpful to load the driver with
648	`probe_only=1` option (at best after the cold reboot) and run
649	alsa-info at this state.  With this option, the driver won't configure
650	the mixer and PCM but just tries to probe the codec slot.  After
651	probing, the proc file is available, so you can get the raw codec
652	information before modified by the driver.  Of course, the driver
653	isn't usable with `probe_only=1`.  But you can continue the
654	configuration via hwdep sysfs file if hda-reconfig option is enabled.
655	Using `probe_only` mask 2 skips the reset of HDA codecs (use
656	`probe_only=3` as module option). The hwdep interface can be used
657	to determine the BIOS codec initialization.
658	
659	
660	hda-verb
661	~~~~~~~~
662	hda-verb is a tiny program that allows you to access the HD-audio
663	codec directly.  You can execute a raw HD-audio codec verb with this.
664	This program accesses the hwdep device, thus you need to enable the
665	kernel config `CONFIG_SND_HDA_HWDEP=y` beforehand.
666	
667	The hda-verb program takes four arguments: the hwdep device file, the
668	widget NID, the verb and the parameter.  When you access to the codec
669	on the slot 2 of the card 0, pass /dev/snd/hwC0D2 to the first
670	argument, typically.  (However, the real path name depends on the
671	system.)
672	
673	The second parameter is the widget number-id to access.  The third
674	parameter can be either a hex/digit number or a string corresponding
675	to a verb.  Similarly, the last parameter is the value to write, or
676	can be a string for the parameter type.
677	
678	------------------------------------------------------------------------
679	  % hda-verb /dev/snd/hwC0D0 0x12 0x701 2
680	  nid = 0x12, verb = 0x701, param = 0x2
681	  value = 0x0
682	
683	  % hda-verb /dev/snd/hwC0D0 0x0 PARAMETERS VENDOR_ID
684	  nid = 0x0, verb = 0xf00, param = 0x0
685	  value = 0x10ec0262
686	
687	  % hda-verb /dev/snd/hwC0D0 2 set_a 0xb080
688	  nid = 0x2, verb = 0x300, param = 0xb080
689	  value = 0x0
690	------------------------------------------------------------------------
691	
692	Although you can issue any verbs with this program, the driver state
693	won't be always updated.  For example, the volume values are usually
694	cached in the driver, and thus changing the widget amp value directly
695	via hda-verb won't change the mixer value.
696	
697	The hda-verb program is found in the ftp directory:
698	
699	- ftp://ftp.suse.com/pub/people/tiwai/misc/
700	
701	Also a git repository is available:
702	
703	- git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/hda-verb.git
704	
705	See README file in the tarball for more details about hda-verb
706	program.
707	
708	
709	hda-analyzer
710	~~~~~~~~~~~~
711	hda-analyzer provides a graphical interface to access the raw HD-audio
712	control, based on pyGTK2 binding.  It's a more powerful version of
713	hda-verb.  The program gives you an easy-to-use GUI stuff for showing
714	the widget information and adjusting the amp values, as well as the
715	proc-compatible output.
716	
717	The hda-analyzer:
718	
719	- http://git.alsa-project.org/?p=alsa.git;a=tree;f=hda-analyzer
720	
721	is a part of alsa.git repository in alsa-project.org:
722	
723	- git://git.alsa-project.org/alsa.git
724	
725	Codecgraph
726	~~~~~~~~~~
727	Codecgraph is a utility program to generate a graph and visualizes the
728	codec-node connection of a codec chip.  It's especially useful when
729	you analyze or debug a codec without a proper datasheet.  The program
730	parses the given codec proc file and converts to SVG via graphiz
731	program.
732	
733	The tarball and GIT trees are found in the web page at:
734	
735	- http://helllabs.org/codecgraph/
736	
737	
738	hda-emu
739	~~~~~~~
740	hda-emu is an HD-audio emulator.  The main purpose of this program is
741	to debug an HD-audio codec without the real hardware.  Thus, it
742	doesn't emulate the behavior with the real audio I/O, but it just
743	dumps the codec register changes and the ALSA-driver internal changes
744	at probing and operating the HD-audio driver.
745	
746	The program requires a codec proc-file to simulate.  Get a proc file
747	for the target codec beforehand, or pick up an example codec from the
748	codec proc collections in the tarball.  Then, run the program with the
749	proc file, and the hda-emu program will start parsing the codec file
750	and simulates the HD-audio driver:
751	
752	------------------------------------------------------------------------
753	  % hda-emu codecs/stac9200-dell-d820-laptop
754	  # Parsing..
755	  hda_codec: Unknown model for STAC9200, using BIOS defaults
756	  hda_codec: pin nid 08 bios pin config 40c003fa
757	  ....
758	------------------------------------------------------------------------
759	
760	The program gives you only a very dumb command-line interface.  You
761	can get a proc-file dump at the current state, get a list of control
762	(mixer) elements, set/get the control element value, simulate the PCM
763	operation, the jack plugging simulation, etc.
764	
765	The package is found in:
766	
767	- ftp://ftp.suse.com/pub/people/tiwai/misc/
768	
769	A git repository is available:
770	
771	- git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/hda-emu.git
772	
773	See README file in the tarball for more details about hda-emu
774	program.
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