[Letux-kernel] twl gpios / headset detect on gta04a5

[Andreas Kemnade]

On Sun, 23 Sep 2018 19:32:34 +0200
"H. Nikolaus Schaller" <hns at goldelico.com> wrote:

> Hi,
> 
> > Am 23.09.2018 um 18:51 schrieb Andreas Kemnade <andreas at kemnade.info>:
> > 
> > Hi,
> > 
> > I am looking at the headset stuff.
> > The detection is at gpio492 on gta04a5 if I
> > understand everything right.
> > I exported that and no reaction there on plugging
> > And then I am wondering:
> > root at gta04:/sys/class/gpio/gpio492# twl-i2c.sh GPIO r 0x13
> > 0x00
> > # twl-i2c.sh GPIO r 0x14
> > 0x00
> > 
> > No pullups/downs enabled?!
> > Hmm, floating inputs there?!
> > 
> > twl-i2c.sh GPIO w 0x13 0x20
> > 
> > does the trick. the exported gpio shows values.  
> 
> Good finding!
> 
> > But are the pullup/down
> > values correct there?  
> 
> According to schematics:
> 
> 	http://projects.goldelico.com/p/gta04-main/downloads/48/
> 
> there is a 10k from the gpio to the switch and a 10k pull-down.
> 
> So there should be a pull-up for the gpio to provide energy.
Well, that is one thing. I enabled the pullup using:

twl-i2c.sh GPIO w 0x13 0x20

More interesting are the *other* twl gpio pins. Floating stuff
might be there. And therefore unecessary suspend currents.

> 
> Then,
> - if the headset is connected, the switch is open and the gpio should read "1"
> - while a disconnected headset should connect the gpio to gnd through 20k which should be (note, this circuit has never been tested!) read as "0".
> 
That is wrong. It is tested be my now.

Regards,
Andreas


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