lkml.org 
[lkml]   [2019]   [Mar]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] pinctrl: intel: Implements gpio free function
On Thu, Mar 21, 2019 at 10:44:20AM +0200, Mika Westerberg wrote:
> On Thu, Mar 21, 2019 at 10:35:24AM +0800, zhuchangchun wrote:
> > When we use the gpio to control some peripheral devices,and try to
> > export the gpio first,then unexport the gpio, we test the signal with
> > oscilloscope,and find the signal can't meet the requirements,because
> > after we unexported the gpio,the gpio's register(tx and rx)value can't
> > be recovered,and this will infruence the device work flow.
>
> After you unexport GPIO it can go back to any previous mode it was. If
> you need to use it as GPIO then why unexport it in the first place?

...and on top of that GPIO sysfs interface is deprecated.

> > We check the gpio's unexport code work flow, then find the gpio's free
> > hook function has not been implemented, After we add pinmux_ops' free
> > function to set exported gpio to recover its original value,the problem
> > is fixed.
>
> I don't think this is what ->free callback should do (assuming we decide
> to implement it since we don't implement ->release either). It is
> supposed to reverse effects of ->request which is what it currently does ;-)

Exactly!

--
With Best Regards,
Andy Shevchenko


\
 
 \ /
  Last update: 2019-03-21 10:24    [W:0.117 / U:0.040 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site