Nokia N900 headset detection & MIC Bias + TVOUT

Nokia N900 headset detection & MIC Bias + TVOUT

[Pali Rohár]

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Hi!

For jack cable and headset detection in Nokia N900 I would need to 
enable/disable MIC Bias and also enable/disable TVOUT output.

All that is needed in N900 sound driver, file sound/soc/omap/rx51.c. Can 
you help me which functions should I call to enable/disable it 
correctly? In headset detection code I need to be sure that nobody 
(other kernel drivers or userspace via alsamixer) except current 
function could change Bias settings.

MIC Bias is controlled by MICBIAS_CTRL in aic34 'B' part codec, file 
tlv320aic3x.c.

And according to RX-51 Schematics TVOUT is controlled by OMAP3430 pins: 
TV_OUT1 and TV_VFB1. I have not found any references to them in kernel, 
just in omap trm. How is OMAP3430's TV_OUT1 controlled?

(Existing code in Maemo 2.6.28 kernel is doing it by big hack - exports 
function which directly modify MICBIAS_CTRL)

-- 
Pali Rohár
pali.rohar@gmail.com

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Re: Nokia N900 headset detection & MIC Bias + TVOUT

[Mark Brown]

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On Sat, Jan 07, 2017 at 12:07:49AM +0100, Pali Rohár wrote:

> All that is needed in N900 sound driver, file sound/soc/omap/rx51.c. Can 
> you help me which functions should I call to enable/disable it 
> correctly? In headset detection code I need to be sure that nobody 
> (other kernel drivers or userspace via alsamixer) except current 
> function could change Bias settings.

> MIC Bias is controlled by MICBIAS_CTRL in aic34 'B' part codec, file 
> tlv320aic3x.c.

Microphone biases are normally controlled by supply widgets and managed
via DAPM.  You can see quite a few examples of this in existing drivers.

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Re: Nokia N900 headset detection & MIC Bias + TVOUT

[Pali Rohár]

On Monday 09 January 2017 11:27:49 Mark Brown wrote:
> On Sat, Jan 07, 2017 at 12:07:49AM +0100, Pali Rohár wrote:
> 
> > All that is needed in N900 sound driver, file sound/soc/omap/rx51.c. Can 
> > you help me which functions should I call to enable/disable it 
> > correctly? In headset detection code I need to be sure that nobody 
> > (other kernel drivers or userspace via alsamixer) except current 
> > function could change Bias settings.
> 
> > MIC Bias is controlled by MICBIAS_CTRL in aic34 'B' part codec, file 
> > tlv320aic3x.c.
> 
> Microphone biases are normally controlled by supply widgets and managed
> via DAPM.  You can see quite a few examples of this in existing drivers.

So... can I call snd_soc_dapm_mutex_lock(dapm) at function startup,
start doing cable detection and when needed call this?

snd_soc_dapm_enable_pin_unlocked(dapm, "HS Mic");
snd_soc_dapm_sync_unlocked(dapm);

And at the end of function revert back "HS Mic" pin status and call
snd_soc_dapm_mutex_unlock(dapm)?

-- 
Pali Rohár
pali.rohar@gmail.com

Re: Nokia N900 headset detection & MIC Bias + TVOUT

[Mark Brown]

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On Mon, Jan 09, 2017 at 02:13:17PM +0100, Pali Rohár wrote:

> So... can I call snd_soc_dapm_mutex_lock(dapm) at function startup,
> start doing cable detection and when needed call this?

> snd_soc_dapm_enable_pin_unlocked(dapm, "HS Mic");
> snd_soc_dapm_sync_unlocked(dapm);

> And at the end of function revert back "HS Mic" pin status and call
> snd_soc_dapm_mutex_unlock(dapm)?

You shouldn't need to lock I'd expect, and you'll want to sync at any
point where you need an actual change.  Note that if something holds the
microphone bias on (like something using the microphone) separately then
that'll take effect so if you really need things to get turned off then
that won't work but you probably have trouble anyway in that situation.

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Re: Nokia N900 headset detection & MIC Bias + TVOUT

[Pali Rohár]

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On Monday 09 January 2017 20:22:01 Mark Brown wrote:
> On Mon, Jan 09, 2017 at 02:13:17PM +0100, Pali Rohár wrote:
> > So... can I call snd_soc_dapm_mutex_lock(dapm) at function startup,
> > start doing cable detection and when needed call this?
> > 
> > snd_soc_dapm_enable_pin_unlocked(dapm, "HS Mic");
> > snd_soc_dapm_sync_unlocked(dapm);
> > 
> > And at the end of function revert back "HS Mic" pin status and call
> > snd_soc_dapm_mutex_unlock(dapm)?
> 
> You shouldn't need to lock I'd expect, and you'll want to sync at any
> point where you need an actual change.  Note that if something holds
> the microphone bias on (like something using the microphone)
> separately then that'll take effect so if you really need things to
> get turned off then that won't work but you probably have trouble
> anyway in that situation.

This is needed for cable/jack detection at time when jack is inserted. 
So before it there cannot be any user of (disconnected) microphone.

What I need is to enable mic bias, measure ADC of some time period, 
check status of some GPIOs. Then disable mic bias, measure ADC again and 
check GPIOs. I in this detection procedure I need to ensure that nobody 
changes mic bias. So I though that locking the whole procedure could 
ensure that.

-- 
Pali Rohár
pali.rohar@gmail.com

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Re: Nokia N900 headset detection & MIC Bias + TVOUT

[Mark Brown]

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On Mon, Jan 09, 2017 at 08:29:53PM +0100, Pali Rohár wrote:
> On Monday 09 January 2017 20:22:01 Mark Brown wrote:

> > point where you need an actual change.  Note that if something holds
> > the microphone bias on (like something using the microphone)
> > separately then that'll take effect so if you really need things to
> > get turned off then that won't work but you probably have trouble
> > anyway in that situation.

> This is needed for cable/jack detection at time when jack is inserted. 
> So before it there cannot be any user of (disconnected) microphone.

That's not going to stop userspace, consider what happens if the headset
gets removed and userspace is slow to stop a recording for example.

> What I need is to enable mic bias, measure ADC of some time period, 
> check status of some GPIOs. Then disable mic bias, measure ADC again and 
> check GPIOs. I in this detection procedure I need to ensure that nobody 
> changes mic bias. So I though that locking the whole procedure could 
> ensure that.

That sounds racy and a bit unusual - what's the actual procedure here?

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Re: Nokia N900 headset detection & MIC Bias + TVOUT

[Pali Rohár]

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On Monday 09 January 2017 20:38:28 Mark Brown wrote:
> On Mon, Jan 09, 2017 at 08:29:53PM +0100, Pali Rohár wrote:
> > On Monday 09 January 2017 20:22:01 Mark Brown wrote:
> > > point where you need an actual change.  Note that if something
> > > holds the microphone bias on (like something using the
> > > microphone) separately then that'll take effect so if you really
> > > need things to get turned off then that won't work but you
> > > probably have trouble anyway in that situation.
> > 
> > This is needed for cable/jack detection at time when jack is
> > inserted. So before it there cannot be any user of (disconnected)
> > microphone.
> 
> That's not going to stop userspace, consider what happens if the
> headset gets removed and userspace is slow to stop a recording for
> example.

Ok. But in this case changing mic bias does not introduce any problems
as userspace already trying to record from disconnected microphone.

> > What I need is to enable mic bias, measure ADC of some time period,
> > check status of some GPIOs. Then disable mic bias, measure ADC
> > again and check GPIOs. I in this detection procedure I need to
> > ensure that nobody changes mic bias. So I though that locking the
> > whole procedure could ensure that.
> 
> That sounds racy and a bit unusual - what's the actual procedure
> here?

The whole old code for production Nokia N900 devices is there:
https://github.com/pali/linux-n900/blob/v2.6.28-nokia/drivers/misc/nokia-av.c

If it is usual/unusual/crazy/wtf/:-) I can just tell: it is working fine
with that Maemo 2.6.28 production kernel. And there is no documentation
for it, just code. So the best what we can do is reimplement that driver
for mainline kernel and check if it is working. (Then we can maybe start
changing logic if something make sense...).

It is more complicated, but basic idea seems to be:

Use interrupt handler when jack_detection_gpio changes. When 1 --> jack
unplugged (no detection is needed), otherwise plugged and start
detection.

Start: set eci_sw_gpio to 1, enable mic bias, wait 20msec

Detection point 1: if eci0_gpio is 1 then goto Detection point 3

Detection point 2: measure ECI_ADC (thresholds define type) and goto Stop

Detection point 3: set eci_sw_gpio to 0, wait 20msec, if eci1_gpio is 1 then goto Stop (open cable 
was inserted)

Detection point 4: set eci_sw_gpio to 1, disable mic bias, measure ECI_ADC until it stabilize 
(thresholds define type)

Stop: set eci_sw_gpio to 1, revert mic bias

Thresholds for Detection point 2 are defined as:
#define THRESHOLD_GROUNDED	40		// HEADPHONES or line input cable or external mic
#define THRESHOLD_VIDEO_HI	150		// VIDEO_CABLE

Thresholds for Detection point 4 are defined as:
#define THRESHOLD_HEADSET_HI	1000	// BASIC_HEADSET

(probably threshold for basic headset is not correct)

The whole procedure is repeated 5-10 times. If open cable is detected
then eci_sw_gpio is set to 0 and procedure is periodically repeated
after some interval (looking at the code I think that interrupt for
eci1_gpio could be used instead of busy waiting). Optionally if nothing
(= unknown) after 5-10 times is detected then another procedure for ECI
headsets could be used. As Joerg pointed that nokia-av.c code has
incorrect detection for ECI it first needs to be investigated. But it
will need to disable TVOUT (OMAP3430 TV_OUT1 and TV_VFB1 pins).

-- 
Pali Rohár
pali.rohar@gmail.com

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