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Based on kernel version 3.13. Page generated on 2014-01-20 22:04 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 controllers.  The capture stream position is corrected
63	by comparing both LPIB and position-buffer values.
64	`position_fix=4` is another combination available for all controllers,
65	and uses LPIB for the playback and the position-buffer for the capture
66	streams.
67	0 is the default value for all other
68	controllers, the automatic check and fallback to LPIB as described in
69	the above.  If you get a problem of repeated sounds, this option might
70	help.
71	
72	In addition to that, every controller is known to be broken regarding
73	the wake-up timing.  It wakes up a few samples before actually
74	processing the data on the buffer.  This caused a lot of problems, for
75	example, with ALSA dmix or JACK.  Since 2.6.27 kernel, the driver puts
76	an artificial delay to the wake up timing.  This delay is controlled
77	via `bdl_pos_adj` option. 
78	
79	When `bdl_pos_adj` is a negative value (as default), it's assigned to
80	an appropriate value depending on the controller chip.  For Intel
81	chips, it'd be 1 while it'd be 32 for others.  Usually this works.
82	Only in case it doesn't work and you get warning messages, you should
83	change this parameter to other values.
84	
85	
86	Codec-Probing Problem
87	~~~~~~~~~~~~~~~~~~~~~
88	A less often but a more severe problem is the codec probing.  When
89	BIOS reports the available codec slots wrongly, the driver gets
90	confused and tries to access the non-existing codec slot.  This often
91	results in the total screw-up, and destructs the further communication
92	with the codec chips.  The symptom appears usually as error messages
93	like:
94	------------------------------------------------------------------------
95	  hda_intel: azx_get_response timeout, switching to polling mode:
96	        last cmd=0x12345678
97	  hda_intel: azx_get_response timeout, switching to single_cmd mode:
98	        last cmd=0x12345678
99	------------------------------------------------------------------------
100	
101	The first line is a warning, and this is usually relatively harmless.
102	It means that the codec response isn't notified via an IRQ.  The
103	driver uses explicit polling method to read the response.  It gives
104	very slight CPU overhead, but you'd unlikely notice it.
105	
106	The second line is, however, a fatal error.  If this happens, usually
107	it means that something is really wrong.  Most likely you are
108	accessing a non-existing codec slot.
109	
110	Thus, if the second error message appears, try to narrow the probed
111	codec slots via `probe_mask` option.  It's a bitmask, and each bit
112	corresponds to the codec slot.  For example, to probe only the first
113	slot, pass `probe_mask=1`.  For the first and the third slots, pass
114	`probe_mask=5` (where 5 = 1 | 4), and so on.
115	
116	Since 2.6.29 kernel, the driver has a more robust probing method, so
117	this error might happen rarely, though.
118	
119	On a machine with a broken BIOS, sometimes you need to force the
120	driver to probe the codec slots the hardware doesn't report for use.
121	In such a case, turn the bit 8 (0x100) of `probe_mask` option on.
122	Then the rest 8 bits are passed as the codec slots to probe
123	unconditionally.  For example, `probe_mask=0x103` will force to probe
124	the codec slots 0 and 1 no matter what the hardware reports.
125	
126	
127	Interrupt Handling
128	~~~~~~~~~~~~~~~~~~
129	HD-audio driver uses MSI as default (if available) since 2.6.33
130	kernel as MSI works better on some machines, and in general, it's
131	better for performance.  However, Nvidia controllers showed bad
132	regressions with MSI (especially in a combination with AMD chipset),
133	thus we disabled MSI for them.
134	
135	There seem also still other devices that don't work with MSI.  If you
136	see a regression wrt the sound quality (stuttering, etc) or a lock-up
137	in the recent kernel, try to pass `enable_msi=0` option to disable
138	MSI.  If it works, you can add the known bad device to the blacklist
139	defined in hda_intel.c.  In such a case, please report and give the
140	patch back to the upstream developer. 
141	
142	
143	HD-AUDIO CODEC
144	--------------
145	
146	Model Option
147	~~~~~~~~~~~~
148	The most common problem regarding the HD-audio driver is the
149	unsupported codec features or the mismatched device configuration.
150	Most of codec-specific code has several preset models, either to
151	override the BIOS setup or to provide more comprehensive features.
152	
153	The driver checks PCI SSID and looks through the static configuration
154	table until any matching entry is found.  If you have a new machine,
155	you may see a message like below:
156	------------------------------------------------------------------------
157	    hda_codec: ALC880: BIOS auto-probing.
158	------------------------------------------------------------------------
159	Meanwhile, in the earlier versions, you would see a message like:
160	------------------------------------------------------------------------
161	    hda_codec: Unknown model for ALC880, trying auto-probe from BIOS...
162	------------------------------------------------------------------------
163	Even if you see such a message, DON'T PANIC.  Take a deep breath and
164	keep your towel.  First of all, it's an informational message, no
165	warning, no error.  This means that the PCI SSID of your device isn't
166	listed in the known preset model (white-)list.  But, this doesn't mean
167	that the driver is broken.  Many codec-drivers provide the automatic
168	configuration mechanism based on the BIOS setup.
169	
170	The HD-audio codec has usually "pin" widgets, and BIOS sets the default
171	configuration of each pin, which indicates the location, the
172	connection type, the jack color, etc.  The HD-audio driver can guess
173	the right connection judging from these default configuration values.
174	However -- some codec-support codes, such as patch_analog.c, don't
175	support the automatic probing (yet as of 2.6.28).  And, BIOS is often,
176	yes, pretty often broken.  It sets up wrong values and screws up the
177	driver.
178	
179	The preset model (or recently called as "fix-up") is provided
180	basically to overcome such a situation.  When the matching preset
181	model is found in the white-list, the driver assumes the static
182	configuration of that preset with the correct pin setup, etc.
183	Thus, if you have a newer machine with a slightly different PCI SSID
184	(or codec SSID) from the existing one, you may have a good chance to
185	re-use the same model.  You can pass the `model` option to specify the
186	preset model instead of PCI (and codec-) SSID look-up.
187	
188	What `model` option values are available depends on the codec chip.
189	Check your codec chip from the codec proc file (see "Codec Proc-File"
190	section below).  It will show the vendor/product name of your codec
191	chip.  Then, see Documentation/sound/alsa/HD-Audio-Models.txt file,
192	the section of HD-audio driver.  You can find a list of codecs
193	and `model` options belonging to each codec.  For example, for Realtek
194	ALC262 codec chip, pass `model=ultra` for devices that are compatible
195	with Samsung Q1 Ultra.
196	
197	Thus, the first thing you can do for any brand-new, unsupported and
198	non-working HD-audio hardware is to check HD-audio codec and several
199	different `model` option values.  If you have any luck, some of them
200	might suit with your device well.
201	
202	There are a few special model option values:
203	- when 'nofixup' is passed, the device-specific fixups in the codec
204	  parser are skipped.
205	- when `generic` is passed, the codec-specific parser is skipped and
206	  only the generic parser is used.
207	
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 `jack_detect = no`
386	  will disable the jack detection of the machine completely.
387	init_pin_configs::
388	  Shows the initial pin default config values set by BIOS.
389	driver_pin_configs::
390	  Shows the pin default values set by the codec parser explicitly.
391	  This doesn't show all pin values but only the changed values by
392	  the parser.  That is, if the parser doesn't change the pin default
393	  config values by itself, this will contain nothing.
394	user_pin_configs::
395	  Shows the pin default config values to override the BIOS setup.
396	  Writing this (with two numbers, NID and value) appends the new
397	  value.  The given will be used instead of the initial BIOS value at
398	  the next reconfiguration time.  Note that this config will override
399	  even the driver pin configs, too.
400	reconfig::
401	  Triggers the codec re-configuration.  When any value is written to
402	  this file, the driver re-initialize and parses the codec tree
403	  again.  All the changes done by the sysfs entries above are taken
404	  into account.
405	clear::
406	  Resets the codec, removes the mixer elements and PCM stuff of the
407	  specified codec, and clear all init verbs and hints.
408	
409	For example, when you want to change the pin default configuration
410	value of the pin widget 0x14 to 0x9993013f, and let the driver
411	re-configure based on that state, run like below:
412	------------------------------------------------------------------------
413	  # echo 0x14 0x9993013f > /sys/class/sound/hwC0D0/user_pin_configs
414	  # echo 1 > /sys/class/sound/hwC0D0/reconfig  
415	------------------------------------------------------------------------
416	
417	
418	Hint Strings
419	~~~~~~~~~~~~
420	The codec parser have several switches and adjustment knobs for
421	matching better with the actual codec or device behavior.  Many of
422	them can be adjusted dynamically via "hints" strings as mentioned in
423	the section above.  For example, by passing `jack_detect = no` string
424	via sysfs or a patch file, you can disable the jack detection, thus
425	the codec parser will skip the features like auto-mute or mic
426	auto-switch.  As a boolean value, either `yes`, `no`, `true`, `false`,
427	`1` or `0` can be passed.
428	
429	The generic parser supports the following hints:
430	
431	- jack_detect (bool): specify whether the jack detection is available
432	  at all on this machine; default true
433	- inv_jack_detect (bool): indicates that the jack detection logic is
434	  inverted
435	- trigger_sense (bool): indicates that the jack detection needs the
436	  explicit call of AC_VERB_SET_PIN_SENSE verb
437	- inv_eapd (bool): indicates that the EAPD is implemented in the
438	  inverted logic
439	- pcm_format_first (bool): sets the PCM format before the stream tag
440	  and channel ID
441	- sticky_stream (bool): keep the PCM format, stream tag and ID as long
442	  as possible; default true
443	- spdif_status_reset (bool): reset the SPDIF status bits at each time
444	  the SPDIF stream is set up
445	-  pin_amp_workaround (bool): the output pin may have multiple amp
446	  values
447	- single_adc_amp (bool): ADCs can have only single input amps
448	- auto_mute (bool): enable/disable the headphone auto-mute feature;
449	  default true
450	- auto_mic (bool): enable/disable the mic auto-switch feature; default
451	  true
452	- line_in_auto_switch (bool): enable/disable the line-in auto-switch
453	  feature; default false
454	- need_dac_fix (bool): limits the DACs depending on the channel count
455	- primary_hp (bool): probe headphone jacks as the primary outputs;
456	  default true
457	- multi_io (bool): try probing multi-I/O config (e.g. shared
458	  line-in/surround, mic/clfe jacks)
459	- multi_cap_vol (bool): provide multiple capture volumes
460	- inv_dmic_split (bool): provide split internal mic volume/switch for
461	  phase-inverted digital mics
462	- indep_hp (bool): provide the independent headphone PCM stream and
463	  the corresponding mixer control, if available
464	- add_stereo_mix_input (bool): add the stereo mix (analog-loopback
465	  mix) to the input mux if available
466	- add_jack_modes (bool): add "xxx Jack Mode" enum controls to each
467	  I/O jack for allowing to change the headphone amp and mic bias VREF
468	  capabilities
469	- power_down_unused (bool): power down the unused widgets
470	- add_hp_mic (bool): add the headphone to capture source if possible
471	- hp_mic_detect (bool): enable/disable the hp/mic shared input for a
472	  single built-in mic case; default true
473	- mixer_nid (int): specifies the widget NID of the analog-loopback
474	  mixer
475	
476	
477	Early Patching
478	~~~~~~~~~~~~~~
479	When CONFIG_SND_HDA_PATCH_LOADER=y is set, you can pass a "patch" as a
480	firmware file for modifying the HD-audio setup before initializing the
481	codec.  This can work basically like the reconfiguration via sysfs in
482	the above, but it does it before the first codec configuration.
483	
484	A patch file is a plain text file which looks like below:
485	
486	------------------------------------------------------------------------
487	  [codec]
488	  0x12345678 0xabcd1234 2
489	
490	  [model]
491	  auto
492	
493	  [pincfg]
494	  0x12 0x411111f0
495	
496	  [verb]
497	  0x20 0x500 0x03
498	  0x20 0x400 0xff
499	
500	  [hint]
501	  jack_detect = no
502	------------------------------------------------------------------------
503	
504	The file needs to have a line `[codec]`.  The next line should contain
505	three numbers indicating the codec vendor-id (0x12345678 in the
506	example), the codec subsystem-id (0xabcd1234) and the address (2) of
507	the codec.  The rest patch entries are applied to this specified codec
508	until another codec entry is given.  Passing 0 or a negative number to
509	the first or the second value will make the check of the corresponding
510	field be skipped.  It'll be useful for really broken devices that don't
511	initialize SSID properly.
512	
513	The `[model]` line allows to change the model name of the each codec.
514	In the example above, it will be changed to model=auto.
515	Note that this overrides the module option.
516	
517	After the `[pincfg]` line, the contents are parsed as the initial
518	default pin-configurations just like `user_pin_configs` sysfs above.
519	The values can be shown in user_pin_configs sysfs file, too.
520	
521	Similarly, the lines after `[verb]` are parsed as `init_verbs`
522	sysfs entries, and the lines after `[hint]` are parsed as `hints`
523	sysfs entries, respectively.
524	
525	Another example to override the codec vendor id from 0x12345678 to
526	0xdeadbeef is like below:
527	------------------------------------------------------------------------
528	  [codec]
529	  0x12345678 0xabcd1234 2
530	
531	  [vendor_id]
532	  0xdeadbeef
533	------------------------------------------------------------------------
534	
535	In the similar way, you can override the codec subsystem_id via
536	`[subsystem_id]`, the revision id via `[revision_id]` line.
537	Also, the codec chip name can be rewritten via `[chip_name]` line.
538	------------------------------------------------------------------------
539	  [codec]
540	  0x12345678 0xabcd1234 2
541	
542	  [subsystem_id]
543	  0xffff1111
544	
545	  [revision_id]
546	  0x10
547	
548	  [chip_name]
549	  My-own NEWS-0002
550	------------------------------------------------------------------------
551	
552	The hd-audio driver reads the file via request_firmware().  Thus,
553	a patch file has to be located on the appropriate firmware path,
554	typically, /lib/firmware.  For example, when you pass the option
555	`patch=hda-init.fw`, the file /lib/firmware/hda-init.fw must be
556	present.
557	
558	The patch module option is specific to each card instance, and you
559	need to give one file name for each instance, separated by commas.
560	For example, if you have two cards, one for an on-board analog and one 
561	for an HDMI video board, you may pass patch option like below:
562	------------------------------------------------------------------------
563	    options snd-hda-intel patch=on-board-patch,hdmi-patch
564	------------------------------------------------------------------------
565	
566	
567	Power-Saving
568	~~~~~~~~~~~~
569	The power-saving is a kind of auto-suspend of the device.  When the
570	device is inactive for a certain time, the device is automatically
571	turned off to save the power.  The time to go down is specified via
572	`power_save` module option, and this option can be changed dynamically
573	via sysfs.
574	
575	The power-saving won't work when the analog loopback is enabled on
576	some codecs.  Make sure that you mute all unneeded signal routes when
577	you want the power-saving.
578	
579	The power-saving feature might cause audible click noises at each
580	power-down/up depending on the device.  Some of them might be
581	solvable, but some are hard, I'm afraid.  Some distros such as
582	openSUSE enables the power-saving feature automatically when the power
583	cable is unplugged.  Thus, if you hear noises, suspect first the
584	power-saving.  See /sys/module/snd_hda_intel/parameters/power_save to
585	check the current value.  If it's non-zero, the feature is turned on.
586	
587	The recent kernel supports the runtime PM for the HD-audio controller
588	chip, too.  It means that the HD-audio controller is also powered up /
589	down dynamically.  The feature is enabled only for certain controller
590	chips like Intel LynxPoint.  You can enable/disable this feature
591	forcibly by setting `power_save_controller` option, which is also
592	available at /sys/module/snd_hda_intel/parameters directory.
593	
594	
595	Tracepoints
596	~~~~~~~~~~~
597	The hd-audio driver gives a few basic tracepoints.
598	`hda:hda_send_cmd` traces each CORB write while `hda:hda_get_response`
599	traces the response from RIRB (only when read from the codec driver).
600	`hda:hda_bus_reset` traces the bus-reset due to fatal error, etc,
601	`hda:hda_unsol_event` traces the unsolicited events, and
602	`hda:hda_power_down` and `hda:hda_power_up` trace the power down/up
603	via power-saving behavior.
604	
605	Enabling all tracepoints can be done like
606	------------------------------------------------------------------------
607	  # echo 1 > /sys/kernel/debug/tracing/events/hda/enable
608	------------------------------------------------------------------------
609	then after some commands, you can traces from
610	/sys/kernel/debug/tracing/trace file.  For example, when you want to
611	trace what codec command is sent, enable the tracepoint like:
612	------------------------------------------------------------------------
613	  # cat /sys/kernel/debug/tracing/trace
614	  # tracer: nop
615	  #
616	  #       TASK-PID    CPU#    TIMESTAMP  FUNCTION
617	  #          | |       |          |         |
618	         <...>-7807  [002] 105147.774889: hda_send_cmd: [0:0] val=e3a019
619	         <...>-7807  [002] 105147.774893: hda_send_cmd: [0:0] val=e39019
620	         <...>-7807  [002] 105147.999542: hda_send_cmd: [0:0] val=e3a01a
621	         <...>-7807  [002] 105147.999543: hda_send_cmd: [0:0] val=e3901a
622	         <...>-26764 [001] 349222.837143: hda_send_cmd: [0:0] val=e3a019
623	         <...>-26764 [001] 349222.837148: hda_send_cmd: [0:0] val=e39019
624	         <...>-26764 [001] 349223.058539: hda_send_cmd: [0:0] val=e3a01a
625	         <...>-26764 [001] 349223.058541: hda_send_cmd: [0:0] val=e3901a
626	------------------------------------------------------------------------
627	Here `[0:0]` indicates the card number and the codec address, and
628	`val` shows the value sent to the codec, respectively.  The value is
629	a packed value, and you can decode it via hda-decode-verb program
630	included in hda-emu package below.  For example, the value e3a019 is
631	to set the left output-amp value to 25.
632	------------------------------------------------------------------------
633	  % hda-decode-verb 0xe3a019
634	  raw value = 0x00e3a019
635	  cid = 0, nid = 0x0e, verb = 0x3a0, parm = 0x19
636	  raw value: verb = 0x3a0, parm = 0x19
637	  verbname = set_amp_gain_mute
638	  amp raw val = 0xa019
639	  output, left, idx=0, mute=0, val=25
640	------------------------------------------------------------------------
641	
642	
643	Development Tree
644	~~~~~~~~~~~~~~~~
645	The latest development codes for HD-audio are found on sound git tree:
646	
647	- git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git
648	
649	The master branch or for-next branches can be used as the main
650	development branches in general while the development for the current
651	and next kernels are found in for-linus and for-next branches,
652	respectively.
653	
654	If you are using the latest Linus tree, it'd be better to pull the
655	above GIT tree onto it.  If you are using the older kernels, an easy
656	way to try the latest ALSA code is to build from the snapshot
657	tarball.  There are daily tarballs and the latest snapshot tarball.
658	All can be built just like normal alsa-driver release packages, that
659	is, installed via the usual spells: configure, make and make
660	install(-modules).  See INSTALL in the package.  The snapshot tarballs
661	are found at:
662	
663	- ftp://ftp.suse.com/pub/people/tiwai/snapshot/
664	
665	
666	Sending a Bug Report
667	~~~~~~~~~~~~~~~~~~~~
668	If any model or module options don't work for your device, it's time
669	to send a bug report to the developers.  Give the following in your
670	bug report:
671	
672	- Hardware vendor, product and model names
673	- Kernel version (and ALSA-driver version if you built externally)
674	- `alsa-info.sh` output; run with `--no-upload` option.  See the
675	  section below about alsa-info
676	
677	If it's a regression, at best, send alsa-info outputs of both working
678	and non-working kernels.  This is really helpful because we can
679	compare the codec registers directly.
680	
681	Send a bug report either the followings:
682	
683	kernel-bugzilla::
684	  https://bugzilla.kernel.org/
685	alsa-devel ML::
686	  alsa-devel@alsa-project.org
687	
688	
689	DEBUG TOOLS
690	-----------
691	
692	This section describes some tools available for debugging HD-audio
693	problems.
694	
695	alsa-info
696	~~~~~~~~~
697	The script `alsa-info.sh` is a very useful tool to gather the audio
698	device information.  You can fetch the latest version from:
699	
700	- http://www.alsa-project.org/alsa-info.sh
701	
702	Run this script as root, and it will gather the important information
703	such as the module lists, module parameters, proc file contents
704	including the codec proc files, mixer outputs and the control
705	elements.  As default, it will store the information onto a web server
706	on alsa-project.org.  But, if you send a bug report, it'd be better to
707	run with `--no-upload` option, and attach the generated file.
708	
709	There are some other useful options.  See `--help` option output for
710	details.
711	
712	When a probe error occurs or when the driver obviously assigns a
713	mismatched model, it'd be helpful to load the driver with
714	`probe_only=1` option (at best after the cold reboot) and run
715	alsa-info at this state.  With this option, the driver won't configure
716	the mixer and PCM but just tries to probe the codec slot.  After
717	probing, the proc file is available, so you can get the raw codec
718	information before modified by the driver.  Of course, the driver
719	isn't usable with `probe_only=1`.  But you can continue the
720	configuration via hwdep sysfs file if hda-reconfig option is enabled.
721	Using `probe_only` mask 2 skips the reset of HDA codecs (use
722	`probe_only=3` as module option). The hwdep interface can be used
723	to determine the BIOS codec initialization.
724	
725	
726	hda-verb
727	~~~~~~~~
728	hda-verb is a tiny program that allows you to access the HD-audio
729	codec directly.  You can execute a raw HD-audio codec verb with this.
730	This program accesses the hwdep device, thus you need to enable the
731	kernel config `CONFIG_SND_HDA_HWDEP=y` beforehand.
732	
733	The hda-verb program takes four arguments: the hwdep device file, the
734	widget NID, the verb and the parameter.  When you access to the codec
735	on the slot 2 of the card 0, pass /dev/snd/hwC0D2 to the first
736	argument, typically.  (However, the real path name depends on the
737	system.)
738	
739	The second parameter is the widget number-id to access.  The third
740	parameter can be either a hex/digit number or a string corresponding
741	to a verb.  Similarly, the last parameter is the value to write, or
742	can be a string for the parameter type.
743	
744	------------------------------------------------------------------------
745	  % hda-verb /dev/snd/hwC0D0 0x12 0x701 2
746	  nid = 0x12, verb = 0x701, param = 0x2
747	  value = 0x0
748	
749	  % hda-verb /dev/snd/hwC0D0 0x0 PARAMETERS VENDOR_ID
750	  nid = 0x0, verb = 0xf00, param = 0x0
751	  value = 0x10ec0262
752	
753	  % hda-verb /dev/snd/hwC0D0 2 set_a 0xb080
754	  nid = 0x2, verb = 0x300, param = 0xb080
755	  value = 0x0
756	------------------------------------------------------------------------
757	
758	Although you can issue any verbs with this program, the driver state
759	won't be always updated.  For example, the volume values are usually
760	cached in the driver, and thus changing the widget amp value directly
761	via hda-verb won't change the mixer value.
762	
763	The hda-verb program is included now in alsa-tools:
764	
765	- git://git.alsa-project.org/alsa-tools.git
766	
767	Also, the old stand-alone package is found in the ftp directory:
768	
769	- ftp://ftp.suse.com/pub/people/tiwai/misc/
770	
771	Also a git repository is available:
772	
773	- git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/hda-verb.git
774	
775	See README file in the tarball for more details about hda-verb
776	program.
777	
778	
779	hda-analyzer
780	~~~~~~~~~~~~
781	hda-analyzer provides a graphical interface to access the raw HD-audio
782	control, based on pyGTK2 binding.  It's a more powerful version of
783	hda-verb.  The program gives you an easy-to-use GUI stuff for showing
784	the widget information and adjusting the amp values, as well as the
785	proc-compatible output.
786	
787	The hda-analyzer:
788	
789	- http://git.alsa-project.org/?p=alsa.git;a=tree;f=hda-analyzer
790	
791	is a part of alsa.git repository in alsa-project.org:
792	
793	- git://git.alsa-project.org/alsa.git
794	
795	Codecgraph
796	~~~~~~~~~~
797	Codecgraph is a utility program to generate a graph and visualizes the
798	codec-node connection of a codec chip.  It's especially useful when
799	you analyze or debug a codec without a proper datasheet.  The program
800	parses the given codec proc file and converts to SVG via graphiz
801	program.
802	
803	The tarball and GIT trees are found in the web page at:
804	
805	- http://helllabs.org/codecgraph/
806	
807	
808	hda-emu
809	~~~~~~~
810	hda-emu is an HD-audio emulator.  The main purpose of this program is
811	to debug an HD-audio codec without the real hardware.  Thus, it
812	doesn't emulate the behavior with the real audio I/O, but it just
813	dumps the codec register changes and the ALSA-driver internal changes
814	at probing and operating the HD-audio driver.
815	
816	The program requires a codec proc-file to simulate.  Get a proc file
817	for the target codec beforehand, or pick up an example codec from the
818	codec proc collections in the tarball.  Then, run the program with the
819	proc file, and the hda-emu program will start parsing the codec file
820	and simulates the HD-audio driver:
821	
822	------------------------------------------------------------------------
823	  % hda-emu codecs/stac9200-dell-d820-laptop
824	  # Parsing..
825	  hda_codec: Unknown model for STAC9200, using BIOS defaults
826	  hda_codec: pin nid 08 bios pin config 40c003fa
827	  ....
828	------------------------------------------------------------------------
829	
830	The program gives you only a very dumb command-line interface.  You
831	can get a proc-file dump at the current state, get a list of control
832	(mixer) elements, set/get the control element value, simulate the PCM
833	operation, the jack plugging simulation, etc.
834	
835	The package is found in:
836	
837	- ftp://ftp.suse.com/pub/people/tiwai/misc/
838	
839	A git repository is available:
840	
841	- git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/hda-emu.git
842	
843	See README file in the tarball for more details about hda-emu
844	program.
845	
846	
847	hda-jack-retask
848	~~~~~~~~~~~~~~~
849	hda-jack-retask is a user-friendly GUI program to manipulate the
850	HD-audio pin control for jack retasking.  If you have a problem about
851	the jack assignment, try this program and check whether you can get
852	useful results.  Once when you figure out the proper pin assignment,
853	it can be fixed either in the driver code statically or via passing a
854	firmware patch file (see "Early Patching" section).
855	
856	The program is included in alsa-tools now:
857	
858	- git://git.alsa-project.org/alsa-tools.git
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