[Gta04-owner] Further 3.17 kernel development for GTA04

Dr. H. Nikolaus Schaller hns at goldelico.com
Mon Nov 3 20:04:21 CET 2014


Hi Neil,

Am 03.11.2014 um 14:44 schrieb Dr. H. Nikolaus Schaller <hns at goldelico.com>:

> Hi Neil,
> 
> Am 03.11.2014 um 08:36 schrieb Dr. H. Nikolaus Schaller <hns at goldelico.com>:
> 
>> 
>> Am 03.11.2014 um 08:27 schrieb NeilBrown <neilb at suse.de>:
>> 
>>> On Mon, 3 Nov 2014 07:57:00 +0100 "Dr. H. Nikolaus Schaller"
>>> <hns at goldelico.com> wrote:
>>> 
>>>> 
>>>> Am 03.11.2014 um 07:44 schrieb NeilBrown <neilb at suse.de>:
>>>> 
>>>>> 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?
>>>> 
>>>> Proper device tree based Tri-State control for McBSP to switch between hardware and
>>>> software routing.
>>>> 
>>>> http://projects.goldelico.com/p/gta04-kernel/issues/587/
>>>> 
>>>> And, I had to disable something because I got kernel panics.
>>>> 
>>>> Which sound system did you use? ti,omap-twl4030 or goldelico,gta04-audio?
>>> 
>>> I don't have the goldelico one at all.  Just ti,omap-twl4030 with some
>>> modification to support an external device connected to the voice port.
>>> 
>>> 
>>>> 
>>>> The first one should work out of the box and the second one fails.
>>>> 
>>>>> 
>>>>> 
>>>>>> 
>>>>>>> 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 don’t know either, but that nobody might have to solve the same problem
>>>> as we have to solve.
>>>> 
>>>>> 
>>>>> 
>>>>>> 
>>>>>>> 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
>>>>> chance.
>>>>> 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.
>>>> 
>>>> It is indeed strange. I have added some printk to report hdq write&read and timeouts:
>>>> 
>>>> [    3.894470] omapfb omapfb: no displays
>>>> [    3.899444] omapfb omapfb: failed to setup omapfb
>>>> [    3.904449] platform omapfb: Driver omapfb requests probe deferral
>>>> [    3.912017] platform 4806a000.serial: Driver omap_uart requests probe deferral
>>>> [    3.920532] platform 4806c000.serial: Driver omap_uart requests probe deferral
>>>> [    3.929016] platform 480b4000.mmc: Driver omap_hsmmc requests probe deferral
>>>> [    3.938201] ALSA device list:
>>>> [    3.941314]   No soundcards found.
>>>> [    3.947357] hdq_write_byte(00000027) ok
>>>> [    3.951568] hdq_read_byte -> 00
>>>> [    4.148071] hdq_write_byte timeout
>>>> [    4.350708] hdq_read_byte timeout
>>>> [    4.548431] hdq_write_byte timeout
>>>> [    4.748565] hdq_read_byte timeout
>>>> [    4.948394] hdq_write_byte timeout
>>>> 
>>>> I suspect some other subsystem might be influencing interrupts.
>>>> 
>>>> Something to locate by disabling one driver after the other…
>>> 
>>> Can't explain that.  Both my A3 and A4 boards work.
>>> Maybe watch ‘grep hdq /proc/interrupts' and see if it changes at all.
>> 
>> It says :
>> 
>> 235:         22      INTC  58  omap_hdq
>> 
>> and does not change if I try to cat /sys/class/power_supply/bq27000-battery/voltage_now
>> 
>> So indeed someone is blocking these interrupts. Now I have to identify that “someone” first,
>> but it is easier with a good test case.
> 
> Looks as if I have found it, although I have really no explanation.
> 
> It appears to be related to the DTR patch to omap-serial.c that we have (I think inherited from
> kernel 3.7) to control the virtual GPIO of the w2sg driver. If I checkout the latest from linus/3.18-rc2, hdq works.
> 
> Of course GPS does not work any more, because the DTR control is then missing.
> 
> It appears to be sufficient to add/remove that patch (which is not in mainline Linux - just in
> our 3.18-rc2 and therefore you have no chance to see this effect) to start/stop HDQ interrupts.
> 
> I will report if I get a better understanding why this DTR code can interfere with HDQ and
> which line(s) of code makes the difference.

After a lot of trial and error, I still don’t understand it. But it appears to have something to do
with the UART3 + console handling. There is one line in the driver where the DTR gpio is derived
from the device tree.

If I keep it as is (it reads the “dtr-gpio” property from the DT), we have serial and GPS, but the hdq hangup.
If I force this gpio to 0, hdq works, but the console output goes to the LCD (I have never seen that before), and we have no GPS.
If I force it to -ENOENT (which is equivalent to a DT definition with missing dtr-gpio specification), we have serial and hdq, but no GPS.
If I force it to -EPROBE_DEFER, console goes to LCD. There is no GPS, hdq does not work.

Now, I guess our DTR patch interferes with the takeover of UART3 by this driver. Or alternatively,
that deferred probing in omap_serial has some side-effect for UART0 or UART1.

BR,
Nikolaus


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