From: Michael Lawnick <ml.lawnick@gmx.de>
To: Felipe Balbi <balbi@ti.com>, wsa@the-dreams.de
Cc: Tony Lindgren <tony@atomide.com>, Nishanth Menon <nm@ti.com>,
Dave Gerlach <d-gerlach@ti.com>,
linux-i2c@vger.kernel.org,
Linux OMAP Mailing List <linux-omap@vger.kernel.org>,
Linux ARM Kernel Mailing List
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] i2c: omap: improve duty cycle on SCL
Date: Wed, 17 Jun 2015 13:09:53 +0200 [thread overview]
Message-ID: <55815581.80807@gmx.de> (raw)
In-Reply-To: <1434482276-1210-1-git-send-email-balbi@ti.com>
Am 16.06.2015 um 21:17 schrieb Felipe Balbi:
> With this patch we try to be as close to 50%
> duty cycle as possible. The reason for this
> is that some devices present an erratic behavior
> with certain duty cycles.
>
> One such example is TPS65218 PMIC which fails
> to change voltages when running @ 400kHz and
> duty cycle is lower than 34%.
>
> The idea of the patch is simple:
>
> calculate desired scl_period from requested scl
> and use 50% for tLow and 50% for tHigh.
...
Hmm, and what's about Philips I2C specification 2.1, Jan 2000, Table 5?
> PARAMETER SYMBOL STANDARD-MODE FAST-MODE UNIT
> MIN. MAX. MIN. MAX.
> LOW period of the SCL clock tLOW 4.7 – 1.3 – µs
> HIGH period of the SCL clock tHIGH 4.0 – 0.6 – µs
Your signal is in spec (0.85 µs high, 1,65 low).
Maybe your TPS65218 is just buggy or signals are bad?
--
KR
Michael
--
To unsubscribe from this list: send the line "unsubscribe linux-omap" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
next prev parent reply other threads:[~2015-06-17 11:09 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-16 19:17 [PATCH] i2c: omap: improve duty cycle on SCL Felipe Balbi
2015-06-16 19:19 ` Felipe Balbi
2015-06-17 11:09 ` Michael Lawnick [this message]
[not found] ` <55815581.80807-Mmb7MZpHnFY@public.gmane.org>
2015-06-17 15:38 ` Felipe Balbi
[not found] ` <20150617153812.GB18421-HgARHv6XitJaoMGHk7MhZQC/G2K4zDHf@public.gmane.org>
2015-06-18 6:39 ` Michael Lawnick
2015-06-18 17:24 ` Felipe Balbi
[not found] ` <20150618172428.GB27790-HgARHv6XitJaoMGHk7MhZQC/G2K4zDHf@public.gmane.org>
2015-06-19 5:41 ` Michael Lawnick
[not found] ` <5583AB9D.6090805-Mmb7MZpHnFY@public.gmane.org>
2015-06-19 15:30 ` Felipe Balbi
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=55815581.80807@gmx.de \
--to=ml.lawnick@gmx.de \
--cc=balbi@ti.com \
--cc=d-gerlach@ti.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-i2c@vger.kernel.org \
--cc=linux-omap@vger.kernel.org \
--cc=nm@ti.com \
--cc=tony@atomide.com \
--cc=wsa@the-dreams.de \
/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).