[LinuxPPS] PPS echo implementation

[Rodolfo Giometti]

On 17/09/18 11:32, tom burkart wrote:
> Quoting Rodolfo Giometti <giometti at enneenne.com>:
>> However, you can add extra Raspberry Pi kernel information to our new 
>> LinuxPPS's wiki! :-)
> 
> Sounds like a fair deal ;-)
> Do I send it to you directly?  What format does it need to be in?

We currently use dokuwiki.

>>>>> +        if (of_get_property(np, "enable-pps-echo", NULL)) {
>>>>
>>>> I think we can safely drop property "enable-pps-echo" and considering the 
>>>> EHO functionality activated if property "echo-gpios" is present.
>>>
>>> I elected to provide this functionality as I felt it conceivable that someone 
>>> might want the PPS signal but does not want or require the ECHO functionality.
>>
>> If I well understand this patch when "enable-pps-echo" is enabled you do a 
>> devm_request_threaded_irq(), which in turn calls pps_gpio_irq_threaded() which 
>> requires a GPIO line to work...
> 
> Oh, yes, of course.  Sorry, I misunderstood the first time around.
> 
> Then, if I patch the pps-gpio.dts file directly (as requested), then there will 
> always be  an "echo-gpios" present, which then implies that the ECHO 
> functionality is always enabled.  Will this be an issue?  Or is that why we 
> supply the dts file?

I think you should enable the PPS-echo functionality if and only if someone 
define an echo-gpio...

Ciao,

Rodolfo

-- 

HCE Engineering                      e-mail: giometti at hce-engineering.it
GNU/Linux Solutions                          giometti at enneenne.com
Linux Device Driver                          giometti at linux.it
Embedded Systems                     phone:  +39 349 2432127
UNIX programming                     skype:  rodolfo.giometti
Cosino Project - the quick prototyping embedded system - www.cosino.it
Freelance ICT Italia - Consulente ICT Italia - www.consulenti-ict.it