On Sun, Feb 24, 2019 at 08:27:23AM +0000, Pankaj Bansal wrote:
> This adds device tree binding documentation for generic register based
> multiplexer controlled by a bitfields in a parent device's register range.
>
> Signed-off-by: Pankaj Bansal <pankaj.bansal@xxxxxxx>
> ---
>
> Notes:
> V3:
> - Added the patch in series with the driver patch
> - Fixed the node value out of bitfield error
> - removed the "parent register r/w functions" line
> V2:
> - Removed syscon reference from txt file
> - Removed loading zeroes from hex numbers
> - Fixed the depth of dts nodes
> - fixed minor formatting errors
>
> .../devicetree/bindings/mux/reg-mux.txt | 83 ++++++++++++++++++
> 1 file changed, 83 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/mux/reg-mux.txt b/Documentation/devicetree/bindings/mux/reg-mux.txt
> new file mode 100644
> index 000000000000..8bea6129c113
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mux/reg-mux.txt
> @@ -0,0 +1,83 @@
> +Generic register bitfield-based multiplexer controller bindings
> +
> +Define register bitfields to be used to control multiplexers. The parent
> +device tree node must be a device node to provide register r/w access.
We generally avoid register bit level bindings like this...
What happens when I need 8 or 16-bit accesses. Or some quirky encoding
of the bits. Or non-contiguous bit fields... It's an endless extending
of the binding to try to handle different cases.
> +
> +Required properties:
> +- compatible : "reg-mux"
> +- #mux-control-cells : <1>
> +- mux-reg-masks : an array of register offset and pre-shifted bitfield mask
> + pairs, each describing a single mux control.
> +* Standard mux-controller bindings as decribed in mux-controller.txt
> +
> +Optional properties:
> +- idle-states : if present, the state the muxes will have when idle. The
> + special state MUX_IDLE_AS_IS is the default.
> +
> +The multiplexer state of each multiplexer is defined as the value of the
> +bitfield described by the corresponding register offset and bitfield mask pair
> +in the mux-reg-masks array.
> +
> +Example:
> +
> +&i2c0 {
> + fpga@66 { // fpga connected to i2c
> + compatible = "fsl,lx2160aqds-fpga", "fsl,fpga-qixis-i2c",
> + "simple-mfd";
> + reg = <0x66>;
> +
> + mux: mux-controller { // Mux Producer
> + compatible = "reg-mux";
> + #mux-control-cells = <1>;
> + mux-reg-masks = <0x54 0xf8>, /* 0: reg 0x54, bits 7:3 */
> + <0x54 0x07>; /* 1: reg 0x54, bits 2:0 */
You can accomplish the same thing by moving these 2 properties to the
parent. The parent driver can register a generic mux if that's
appropriate.
Rob
