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

[Mark Rutland]

On Tue, Aug 19, 2014 at 07:34:35PM +0100, atull@xxxxxxxxxxxxxxxxxxxxx wrote:
> From: Alan Tull <atull@xxxxxxxxxxxxxxxxxxxxx>
> 
> 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@xxxxxxxxxxxxxxxxxxxxx>
> ---
>  .../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?

Thanks,
Mark.

>  
>  Optional properties :
>   - i2c-sda-hold-time-ns : should contain the SDA hold time in nanoseconds.
> @@ -29,6 +31,7 @@ Example :
>  		reg = <0xf0000 0x1000>;
>  		interrupts = <11>;
>  		clock-frequency = <400000>;
> +		speed-mode = <0>;
>  	};
>  
>  	i2c@1120000 {
> -- 
> 1.7.9.5
> 
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