From: balbi@ti.com (Felipe Balbi)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] i2c: omap: improve duty cycle on SCL
Date: Tue, 16 Jun 2015 14:19:48 -0500 [thread overview]
Message-ID: <20150616191948.GC30496@saruman.tx.rr.com> (raw)
In-Reply-To: <1434482276-1210-1-git-send-email-balbi@ti.com>
On Tue, Jun 16, 2015 at 02:17:56PM -0500, Felipe Balbi wrote:
> 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.
>
> tLow is calculated with a DIV_ROUND_UP() to make
> sure it's slightly higher than tHigh and to make
> sure that we end up within I2C specifications.
>
> Kudos to Nishanth Menon and Dave Gerlach for helping
> debugging the TPS65218 problem found on AM437x SK.
>
> Signed-off-by: Felipe Balbi <balbi@ti.com>
the patch is correct, but I sent the version written on top of v3.14,
I'll resend correct version, sorry.
--
balbi
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From: Felipe Balbi <balbi@ti.com>
To: Felipe Balbi <balbi@ti.com>
Cc: wsa@the-dreams.de, 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: Tue, 16 Jun 2015 14:19:48 -0500 [thread overview]
Message-ID: <20150616191948.GC30496@saruman.tx.rr.com> (raw)
In-Reply-To: <1434482276-1210-1-git-send-email-balbi@ti.com>
[-- Attachment #1: Type: text/plain, Size: 957 bytes --]
On Tue, Jun 16, 2015 at 02:17:56PM -0500, Felipe Balbi wrote:
> 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.
>
> tLow is calculated with a DIV_ROUND_UP() to make
> sure it's slightly higher than tHigh and to make
> sure that we end up within I2C specifications.
>
> Kudos to Nishanth Menon and Dave Gerlach for helping
> debugging the TPS65218 problem found on AM437x SK.
>
> Signed-off-by: Felipe Balbi <balbi@ti.com>
the patch is correct, but I sent the version written on top of v3.14,
I'll resend correct version, sorry.
--
balbi
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next prev parent reply other threads:[~2015-06-16 19:19 UTC|newest]
Thread overview: 16+ 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 19:17 ` Felipe Balbi
2015-06-16 19:19 ` Felipe Balbi [this message]
2015-06-16 19:19 ` Felipe Balbi
2015-06-17 11:09 ` Michael Lawnick
2015-06-17 11:09 ` Michael Lawnick
2015-06-17 15:38 ` Felipe Balbi
2015-06-17 15:38 ` Felipe Balbi
2015-06-18 6:39 ` Michael Lawnick
2015-06-18 6:39 ` Michael Lawnick
2015-06-18 17:24 ` Felipe Balbi
2015-06-18 17:24 ` Felipe Balbi
2015-06-19 5:41 ` Michael Lawnick
2015-06-19 5:41 ` Michael Lawnick
2015-06-19 15:30 ` Felipe Balbi
2015-06-19 15:30 ` Felipe Balbi
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