linux-kernel - Re: [PATCH 1/2] i2c: designware: device tree bindings for i2c speed mode

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Message-ID: <20140820093621.GC21174@leverpostej>
Date:	Wed, 20 Aug 2014 10:36:21 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	"atull@...nsource.altera.com" <atull@...nsource.altera.com>
Cc:	"wsa@...-dreams.de" <wsa@...-dreams.de>,
	"baruch@...s.co.il" <baruch@...s.co.il>,
	"mika.westerberg@...ux.intel.com" <mika.westerberg@...ux.intel.com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	"skuribay@...ox.com" <skuribay@...ox.com>,
	"Romain.Baeriswyl@...lis.com" <Romain.Baeriswyl@...lis.com>,
	"rafael.j.wysocki@...el.com" <rafael.j.wysocki@...el.com>,
	"alan@...ux.intel.com" <alan@...ux.intel.com>,
	"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"delicious.quinoa@...il.com" <delicious.quinoa@...il.com>,
	"dinguyen@...nsource.altera.com" <dinguyen@...nsource.altera.com>,
	"yvanderv@...nsource.altera.com" <yvanderv@...nsource.altera.com>
Subject: Re: [PATCH 1/2] i2c: designware: device tree bindings for i2c speed
 mode

On Wed, Aug 20, 2014 at 10:34:59AM +0100, Mark Rutland wrote:
> On Tue, Aug 19, 2014 at 07:34:35PM +0100, atull@...nsource.altera.com wrote:
> > From: Alan Tull <atull@...nsource.altera.com>
> > 
> > Add "speed-mode" Device Tree property to select between
> > standard and fast i2c mode.  Previously, driver was hardwired
> > as fast mode.  Default to fast mode if property is not
> > present.
> > 
> > Signed-off-by: Alan Tull <atull@...nsource.altera.com>
> > ---
> >  .../devicetree/bindings/i2c/i2c-designware.txt     |    3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/i2c/i2c-designware.txt b/Documentation/devicetree/bindings/i2c/i2c-designware.txt
> > index 5199b0c..0e4cd21 100644
> > --- a/Documentation/devicetree/bindings/i2c/i2c-designware.txt
> > +++ b/Documentation/devicetree/bindings/i2c/i2c-designware.txt
> > @@ -9,6 +9,8 @@ Required properties :
> >  Recommended properties :
> >  
> >   - clock-frequency : desired I2C bus clock frequency in Hz.
> > + - speed-mode      : 0 = standard (0 - 100Kb/s)
> > +                   : 1 = fast (<= 400Kb/s) <== default
> 
> This is a bit opaque.
> 
> Is this a limit on the max bit-rate the device should operate at?
> 
> Why not just have an optional boolean property to limit to standard
> speed?

I see there's a new patch doing this based on clock-frequency, so feel
free to ignore this.

Mark.
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