[Gta04-owner] Further 3.17 kernel development for GTA04

NeilBrown neilb at suse.de
Mon Nov 3 07:44:03 CET 2014

On Mon, 3 Nov 2014 07:00:42 +0100 "Dr. H. Nikolaus Schaller"
<hns at goldelico.com> wrote:

> Hi,
> Am 02.11.2014 um 10:51 schrieb NeilBrown <neilb at suse.de>:
> > 
> > I've made some useful progress.
> > 
> > Nearly all the things that I need regularly work.  So I can make phone calls
> > (on the GTA04a4, not on the a3),
> ah, did you solve the ALSA sound driver issues?

What ALSA sound driver issues?

> > use the wifi, charge the battery and
> > monitor its status, and turn the GPS on/off using my new approach.  There is
> > no-longer an ‘rfkill' for GPS - opening /dev/ttyO1 does all that is needed.
> Hm. I am not happy that there is no rfkill. Well, someone commented that
> GPS is not a transmitter, but Linux provides the rfkill gps switch (and we have
> not introduced it). And, basically the antenna amplifier might transmit (if it runs
> out of control) so it is safer in an airplane situation to be able to turn off the
> LNA power explicitly. But keep gpsd and tangogps running. A user might
> be just looking into local maps.

It can be added back if it is really needed.
It always thought it was a bit odd as rfkill is, like you say, primarily
about transmitters.

I'd like to know if anyone else is using a 'gps' rfkill  ... I couldn't find
any documentation or useful references last time I looked.

> > I'm not entirely happy with this code yet but it is quite usable.
> > 
> > Suspend seems to work reliably, but power usage is way too high - about
> > 50mA.  There are hints in some patches in 3.18-rc, so USB might be to blame
> > for some of that extra usage, so I'll probably be looking that that when I
> > next get some time.
> > 
> > My kernel doesn't currently "export" the various GPIOs that need to be
> > manually poked.
> > I have this code:
> > 
> >  for l in 186,high 175,high 23,low 21,high
> >  do
> >     g=${l%,*}
> >     echo $g > /sys/class/gpio/export
> >     echo ${l#*,} > /sys/class/gpio/gpio$g/direction
> >  done
> > 
> > in an init.d script which sets some of these up.  GPIO186 is particularly
> > needed for turning the GSM modem on.
> What are these gpios good for? The modem should be controlled through
> rfkill wwan. For this we have prepared a special driver in the gta04-kernel that
> pulses the modem gpio in a similar way as for GPS (there is no UART we can
> use to auto-control modem power).

A driver which I obviously don't have.  I'll try to look at it when I get a
My user-space code wants to poke the gpio, so I provided it.
The others I just provided to I could be certain they were in the correct
position for low power usage.

> > 
> > 
> > I've re-organised my tree as a set of topic branch, mostly based on
> > v3.17, though the 'dts' branch with device-tree changes is based on
> > 
> > git://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap
> >   tag omap-for-v3.17/dt-gta04
> > which has some gta04 stuff that didn't quite make 3.17 - is in 3.18-rc1
> > 
> > The branches are:
> > 
> > 'dts', 'hdq', 'dss', 'pwm-old', 'input', 'hacks', 'wifi', 'extcon', 'itg',
> > ‘tty-slave', 'audio', 'twl4030' and 'charger'
> the hdq patch (there is a missing/wrong compatible entry in the driver) 
> appears to be the last missing piece we have to make it working .
> Does it work for you? I see it start up and read the bq27000 several times,
> but ca. 4.5 seconds after kernel startup it stops. I suspect some IRQ
> interference (maybe from a subsystem that you do not have).

It works very reliably for me.
The behaviour you describe is vaguely reminiscent of problems I was having
ages ago which were due to runtime PM issues with the hdq driver.  I think
the fixes went upstream, possibly
 commit c354a86484b61e32100eb94c1f3f0aa512958cee

Looking at my mail records, the issue was fixed in 3.6.

There was one time recently when reads from one of the sysfs bq27000 files started
returning ENXIO (or maybe ENODEV), but it hasn't happened again.  I'll keep an eye
out for problems.

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