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

[Mark Rutland <mark.rutland-5wv7dgnIgG8@public.gmane.org>]

On Wed, Aug 20, 2014 at 10:34:59AM +0100, Mark Rutland wrote:
> On Tue, Aug 19, 2014 at 07:34:35PM +0100, atull-yzvPICuk2ABMcg4IHK0kFoH6Mc4MB0Vx@public.gmane.org wrote:
> > From: Alan Tull <atull-yzvPICuk2ABMcg4IHK0kFoH6Mc4MB0Vx@public.gmane.org>
> > 
> > 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-yzvPICuk2ABMcg4IHK0kFoH6Mc4MB0Vx@public.gmane.org>
> > ---
> >  .../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.