I took a look at the Intel AC97 2.2 specs. It seems that the behaviour
described here is a AC97 2.2 recommendation. take a look at 1 & 2 of 5.2.1.
Pieter
--------------------------------------------
AC `97 Component Specification Revision 2.2 September 2000
5.2 LINE_OUT and AUX_OUT
AC `97 audio Codecs support two independently controlled stereo outputs:
1. The master output, labeled LINE_OUT, uses pins 35, 36 for L and R
(48 pin QFP package) and is controlled by the Master Volume Register
02h. No changes have been made to LINE_OUT definitions.
2. A second output, originally defined as HP_OUT, uses pins 39, 40,
and 41 for L, Common, and R (48-pin QFP package) was re-defined as
LNLVL_OUT for AC `97 2.1, and is controlled by optional volume Register
04h. In addition to the HP and LNLVL definitions, 4-channel Codecs
typically utilize pins 39 and 41 for the additional (i.e. L & R
Surround) outputs.
5.2.1 AUX_OUT Options
As identified in the previous section, there are three common uses for
AC `97's second output. AC `97 2.2 addresses all three uses by
renaming the second output as AUX_OUT, Register 04h as Aux Out Volume,
and the pins as AUX_OUT_L, AUX_OUT_C, and AUX_OUT_R.
Driver developers should be aware that the AC `97 AUX_OUT may be
implemented in one of three ways:
1.True line level out.Support for a true consumer
equipment-compatible (10 k\Omega ) line level output that does not
change with master volume settings. Either fixed or fixable via the
independent volume controls in Register 04h, the output level provides a
1V RMS (2.8 V peak-to-peak) output level for a 0 dB gain PCM output
stream. When implemented this way, AUX_OUT is equivalent to AC `97 2.1's
LNLVL_OUT definitions.
2.Headphone out. AUX_OUT can be implemented to support integrated
headphone amplifier with 32 \Omega drive capability and independent
volume control via Register 04h. When implemented this way, AUX_OUT is
equivalent to AC `97 1.03 original HP_OUT definitions
3. 4-Channel out. In Codecs that support 4-channel operation,
AUX_OUT can be implemented to support the additional (i.e. L&R
Surround) outputs. When implemented this way, AUX_OUT will be referred
to 4CH_OUT. In 4CH_OUT implementations, L and R Surround output is
controlled via Surround Volume Register 38h, not Aux Out Volume 04h,
and powered down via the PRJ (SDAC) bit in Register 2Ah.
AUX_OUT defaults to be LNLVL_OUT unless HP_OUT or 4CH_OUT support is
detected. Unless the specific Codec configuration is indicated via INF
file, driver writers should use the following methods for detecting a
specialized Codec with HP_OUT or 4CH_OUT capabilities:
* HP_OUT capability can be detected via Reset/ID Register 00h, ID bit 4
and the Aux Out Volume Register 04h default value reads "8000h" (i.e.
implemented). ID4 is no longer used to indicate LNLVL support.
* 4CH output capability can be detected via the Extended Audio ID
Register 28h, SDAC ID bit 7, and a Surround Volume Register 38h default
of "8080h" (i.e. implemented).
HP and LNLVL implementations of AUX_OUT external output are powered down
via bit PR6 in Register 26h.
--------------------------------------
Takashi Iwai wrote:
>At Fri, 24 Jan 2003 12:16:00 +0100 (CET),
>Jaroslav wrote:
>
>
>>On Fri, 24 Jan 2003, Takashi Iwai wrote:
>>
>>
>>
>>>Hi all,
>>>
>>>there have been bug-reports regarding to the swapping of headphone
>>>and master volumes.
>>>i'd like to ask you to check which AC97 codec chip is used on which
>>>board (or laptop) if you have such a problem. if this happens only on
>>>a certain chip model, we can add a quirk for that.
>>>
>>>
>>Takashi, this quirk can be done only by detection of subvendor and
>>subsystem from the PCI ID space.
>>
>>
>
>yeah, the lspci output is on the query list.
>
>
>
>>It's absolutely irrelevant which AC97
>>chip is used.
>>
>>
>
>really? i believe this happens only on certain ac97 chips.
>for example, ALC202 spec says that ALC202A uses the headphone volume
>as the "true line out" volume. so, apparently, some ac97 chips
>"recommend" this behavior. let's see...
>
>
>
>>Vendor might wire codec in any way. Also, some codecs may
>>swap line-out / headphone out via registers.
>>
>>
>
>this is a different case, imo.
>the problem is that we have no chance to detect/switch them, either
>manually or automatically.
>
>a general solution would be to add an ac97 control switch to swap
>them. then the accssed registers are exchanged internally according
>to this control.
>
>but it isn't bad to know which chips and which machines have this
>problem, so that we can add quirks to turn on this switch
>automatically.
>
>
>Takashi
>
>
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