[fedora-arm] beaglebone black GPIO questions

[Bram Van Steenlandt]

op 22-01-15 18:01, Peter Robinson schreef:
> On Thu, Jan 22, 2015 at 4:48 PM, Bram Van Steenlandt <bram at diomedia.be> wrote:
>> Hi,
>>
>> I installed fedora 21 on a beaglebone black, I was amazed how easy this was
>> and how well most things work.
> Good news.
>
>> I can't seem to get GPIO working, first dtc needed a patch for the -@
>> option, after I finally seem to got that working
>> I now find I have no
>> /sys/devices/bone_capemgr* directory.
> The capemgr bits are a custom kernel from BBone that never made it
> upstream. The ability to do DeviceTree overlays only landed mainline
> in 3.19 so you would need at 3.19rc5 [1] or later Fedora kernel. I've
> got as far as testing that the kernel boots on the BBB with the kernel
> with overlays enabled but not had enough time to test them.
Ok, then I would like to avoid them, I'm hoping to also run freebsd in 
the future and I don't think they they will have the device tree overlay 
stuff.
>
>> Can anyone here confirm the status of GPIO (and other cape features) ? does
>> it require a custom kernel ? Am I missing someting ?
> GPIO works, it doesn't need capes to do that. Basically overlays are
> just a means of automating the configuration of all features on a
> particular addon card whether you call it a cape, a hat or an
> expansion board.
>
> Depending on what device you're trying to configure you might just be
> able to do it with a basic script.
output works by doing:
echo 48 > /sys/class/gpio/export
echo out >  /sys/class/gpio/gpio48/direction
echo 1 > /sys/class/gpio/gpio48/value

however, for the input I need to enable the pull up resistor ( I think).

cat /sys/kernel/debug/pinctrl/44e10800.pinmux/pins | grep "pin 46"
pin 46 (44e108b8.0) 00000008 pinctrl-single
I need to change this (00000008) but can't seem to figure out how.
The board I'm trying to use has a dts file saying:
0x030 0x37 /* INPUT MODE7 pullup */
Is there an equivalent to achieve this without a dts file ?

All information I found seems to point either to the device tree overlay 
stuff
or /sys/kernel/debug/omap_mux/gmpc*
all I have here is a subdirectory board which is empty.

Thx

>
> Peter
>
> [1] http://koji.fedoraproject.org/koji/buildinfo?buildID=604938

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