Yes very confusing!  

My kernel does seem to have the off by one issue so &gpio2 is correct.

However isn’t it actually pin 31? 

pin 31 (44e1087c) 00000027 pinctrl-single 

I’m still not getting a PPS input there but am wondering now if the GPS needs a 
fix before it even outputs one at all.

Lee


On 29 January 2014 at 21:05:00, [email protected] ([email protected]) wrote:

On 29/01/14 19:24, Lee Armstrong wrote:  
> Ah ok, I do actually mean to use P8.26 which I think is GPIO1_29.  
>  
> I am using a 3.8 kernel, any way to check at all if it is fixed or not as 
> well?  

It's not a kernel issue as such, it's the way the devicetree has been written.  

Yes, P8.26 is gpio1_29 in the am3359 datasheet and it corresponds to:  
pinctrl-single,pins = <0x7c 0x27 /* P8.26 gpio1_29 */  

0x7c is what tells you that - the register address for gpio1_29 is 0x87c and  
the devicetree encoding uses 0x800 as the base offset.  


Try this:  

root@bbb:~# dtc -I dtb -O dts /boot/am335x-boneblack.dtb | grep gpio  

the four lines at the bottom of the output will be  

gpio1 = "/ocp/gpio@44e07000";  
gpio2 = "/ocp/gpio@4804c000";  
gpio3 = "/ocp/gpio@481ac000";  
gpio4 = "/ocp/gpio@481ae000";  

if the off-by-one problem exists, or  

gpio0 = "/ocp/gpio@44e07000";  
gpio1 = "/ocp/gpio@4804c000";  
gpio2 = "/ocp/gpio@481ac000";  
gpio3 = "/ocp/gpio@481ae000";  

if it doesn't.  

If you have the first set, then in your overlay gpio1_29 would be referred to 
as <&gpio2 29 0>  

Confusing isn't it ?  


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