[PATCH V2 2/2] spi: dual and quad support(device tree)

[Gupta, Pekon]

> 
> Add spi-tmax-nbits and spi-rmax-nbits for spi slave node.
> Modify the related dt document(spi-bus.txt)
>  spi-tmax-nbits:Max number of bits slave will use for MOSI(writting)
>  spi-rmax-nbits:Max number of bits slave will use for MISO(reading)
> Support for spi-tx/rmax-nbits in SPI framework has been picked[1].
> [1]: http://comments.gmane.org/gmane.linux.kernel.spi.devel/14420
> Commit Id:f477b7fb13df2b843997559ff34e87d054ba6538
> 
> Signed-off-by: wangyuhang <wangyuhang2014 at gmail.com>
> ---
>  Documentation/devicetree/bindings/spi/spi-bus.txt |   16
> ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/spi/spi-bus.txt
> b/Documentation/devicetree/bindings/spi/spi-bus.txt
> index 296015e..211336c 100644
> --- a/Documentation/devicetree/bindings/spi/spi-bus.txt
> +++ b/Documentation/devicetree/bindings/spi/spi-bus.txt
> @@ -55,6 +55,22 @@ contain the following properties.
>      		chip select active high
>  - spi-3wire       - (optional) Empty property indicating device requires
>      		    3-wire mode.
> +- spi-tmax-nbits  - (optional) Max number of bits slave will use for
> +    		    MOSI(writting)
> +- spi-rmax-nbits  - (optional) Max number of bits slave will use for
> +    		    MISO(reading)
> +
> +So if for example the slave has 4 wires for writting and 2 wires for reading,
> +and the spi-tx/rx-nbits property should be set as follows:
> +
> +spi-tmax-nbits = <4>;
> +spi-rmax-nbits = <2>;
> +
> +Now the value that spi-tmax-nbits and spi-rmax-nbits can receive is only
> +1(single), 2(dual) and 4(quad). If you don't set spi-tmax-nbits or spi-rmax-
> nbits,
> +spi_device mode will be set in single(1 wire) as default. Another point, if
> +property:spi-3wire is set, spi-t/rmax-nbits is forbidden to set to <2 or 4>,
> +otherwise, an errro will return.
> 
>  If a gpio chipselect is used for the SPI slave the gpio number will be passed
>  via the cs_gpio
> --
> 1.7.9.5

Acked-by: Pekon Gupta <pekon at ti.com>

with regards, pekon