From: Linus Walleij <linus.walleij@linaro.org>
To: Alexander Stein <alexander.stein@systec-electronic.com>
Cc: Gerhard Sittig <gsi@denx.de>,
Daniel Krueger <daniel.krueger@systec-electronic.com>,
Alexandre Courbot <gnurou@gmail.com>,
"linux-gpio@vger.kernel.org" <linux-gpio@vger.kernel.org>
Subject: Re: [PATCH v2] gpio-sch: set output level after configuration of direction
Date: Tue, 22 Apr 2014 13:30:38 +0200 [thread overview]
Message-ID: <CACRpkdZU5ZpM2qwMCNbE5V2mgYHdpA-ECXckk2Y1sU+w6=7XaQ@mail.gmail.com> (raw)
In-Reply-To: <1396873232-19888-1-git-send-email-alexander.stein@systec-electronic.com>
On Mon, Apr 7, 2014 at 2:20 PM, Alexander Stein
<alexander.stein@systec-electronic.com> wrote:
> From: Daniel Krueger <daniel.krueger@systec-electronic.com>
>
> According to the datasheet, writing to the level register has no effect
> when GPIO is programmed as input. Actually the the level register is
> read-only when configured as input. Thus presetting the output level
> before switching to output is _NOT_ possible. Any writes are lost!
> Hence we set the level after configuring the GPIO as output.
> But we cannot prevent a short low pulse if direction is set to high and
> an external pull-up is connected.
>
> Signed-off-by: Daniel Krueger <daniel.krueger@systec-electronic.com>
> Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>
> ---
> Changes in v2:
> * Adjusted commited message to make clear that writes are lost when GPIO
> is configured as input.
No further comments, so I have applied this v2 version for v3.16.
Yours,
Linus Walleij
prev parent reply other threads:[~2014-04-22 11:30 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-25 9:33 [PATCH] gpio-sch: set output level after configuration of direction Alexander Stein
2014-03-26 19:05 ` Gerhard Sittig
2014-03-27 13:10 ` Alexander Stein
2014-03-27 19:05 ` Gerhard Sittig
2014-04-07 12:20 ` [PATCH v2] " Alexander Stein
2014-04-22 11:30 ` Linus Walleij [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CACRpkdZU5ZpM2qwMCNbE5V2mgYHdpA-ECXckk2Y1sU+w6=7XaQ@mail.gmail.com' \
--to=linus.walleij@linaro.org \
--cc=alexander.stein@systec-electronic.com \
--cc=daniel.krueger@systec-electronic.com \
--cc=gnurou@gmail.com \
--cc=gsi@denx.de \
--cc=linux-gpio@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).