[RFC PATCH 04/19] powerpc: wii: device tree

Albert Herranz albert_herranz at yahoo.es
Tue Nov 24 08:55:57 EST 2009

Grant Likely wrote:
> This looks pretty good to me.  The documentation format isn't strict,
> just follow the pattern seen in other bindings.  Make sure you post
> new bindings to devicetree-discuss at lists.ozlabs.org for review.  A
> couple of comments below.

Ok. I know it now for the next time :)

>> Documentation/powerpc/dts-bindings/gpio/i2c.txt
>> GPIO-based I2C
>> Required properties:
>> - compatible : should be "virtual,i2c-gpio".
>> - gpios : should specify GPIOs used for SDA and SCL lines, in that order.
>> - sda-is-open-drain : should be non-zero if SDA gpio is open-drain.
>> - sda-enforce-dir : should be non-zero if SDA gpio must be configured for
>>                    input before reading and for output before writing.
>> - scl-is-open-drain : should be non-zero if SCL gpio is open-drain.
>> - scl-is-output-only : should be non-zero if SCL is an output gpio only.
> Instead of looking for a value in these properties, just make them
> empty properties and change behaviour based on whether or not the
> property is present.

It seems reasonable. Thanks.

> Why is the scl-is-output-only property needed?

It is needed to specify that the I2C master can't honour clock stretching done by I2C slave devices, as it cannot read back SCL.

>> - udelay : signal toggle delay. SCL frequency is (500 / udelay) kHz
> You should follow the lead of
> Documentation/powerpc/dts-bindings/fsl/i2c.txt here and specify a
> clock-frequency property.


>> - timeout : clock stretching timeout in milliseconds.
> I don't understand what this property means.

It is the maximum time that the I2C master should wait for SCL to go high when a I2C slave is "clock-stretching".


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