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

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Date:	Tue, 19 Aug 2014 14:15:21 -0500
From:	Wolfram Sang <wsa@...-dreams.de>
To:	atull@...nsource.altera.com
Cc:	baruch@...s.co.il, mika.westerberg@...ux.intel.com,
	grant.likely@...aro.org, robh+dt@...nel.org, skuribay@...ox.com,
	Romain.Baeriswyl@...lis.com, rafael.j.wysocki@...el.com,
	alan@...ux.intel.com, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	delicious.quinoa@...il.com, dinguyen@...nsource.altera.com,
	yvanderv@...nsource.altera.com
Subject: Re: [PATCH 1/2] i2c: designware: device tree bindings for i2c speed
 mode

On Tue, Aug 19, 2014 at 01:34:35PM -0500, 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.

NACK. This should be deduced from the clock-frequency setting...

> 
> 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.

... which is described here, but surprisingly not supported in the
driver yet :(

Check i2c-riic for an example.

> + - speed-mode      : 0 = standard (0 - 100Kb/s)
> +                   : 1 = fast (<= 400Kb/s) <== default
>  
>  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@...0000 {
> -- 
> 1.7.9.5
> 

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