From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: zhuchangchun <zhuchangchun@cvte.com>,
linus.walleij@linaro.org, linux-gpio@vger.kernel.org,
linux-kernel@vger.kernel.org, hendychu@aliyun.com
Subject: Re: [PATCH] pinctrl: intel: Implements gpio free function
Date: Thu, 21 Mar 2019 11:23:30 +0200 [thread overview]
Message-ID: <20190321092330.GK9224@smile.fi.intel.com> (raw)
In-Reply-To: <20190321084420.GG3622@lahna.fi.intel.com>
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
next prev parent reply other threads:[~2019-03-21 9:23 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-21 2:35 [PATCH] pinctrl: intel: Implements gpio free function zhuchangchun
2019-03-21 8:44 ` Mika Westerberg
2019-03-21 9:23 ` Andy Shevchenko [this message]
2019-03-22 18:32 ` Enrico Weigelt, metux IT consult
2019-03-22 19:06 ` Andy Shevchenko
2019-03-25 9:36 ` Enrico Weigelt, metux IT consult
2019-03-25 11:45 ` Andy Shevchenko
2019-04-03 4:13 ` Linus Walleij
2019-04-04 10:51 ` Enrico Weigelt, metux IT consult
2019-04-04 11:52 ` Andy Shevchenko
2019-04-04 16:03 ` Linus Walleij
[not found] ` <2019032119195575582546@cvte.com>
2019-03-21 12:03 ` Mika Westerberg
[not found] ` <2019032120213955866649@cvte.com>
2019-03-21 12:36 ` Mika Westerberg
[not found] ` <2019032121342663125658@cvte.com>
2019-03-21 13:56 ` Mika Westerberg
[not found] ` <2019032211131426883268@cvte.com>
2019-03-22 10:42 ` Mika Westerberg
[not found] ` <2019032314505202825175@cvte.com>
2019-03-23 16:48 ` andriy.shevchenko
[not found] ` <2019032517511048990383@cvte.com>
2019-03-25 11:48 ` andriy.shevchenko
2019-03-22 18:35 ` Enrico Weigelt, metux IT consult
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