Device Tree configuration for I2C-Multiplexer and its Clients

Device Tree configuration for I2C-Multiplexer and its Clients

[Herzig, Christian]

Hi listmembers!

I'm working on a MPC8360 (powerpc) based target. I'd like to implement
the facility loading drivers for clients behind a I2C multiplexer. 
A driver for the I2C multiplexer family PCA954x is already written by
Rodolfo Giometti.

Let's assume, my hardware looks like that:

                                   ------  ------
                                   |LM75|  |AT24|
                                   |    |  |    |
                       PCA9542     |0x48|  |0x50|
     MPC8360          ---------    ------  -----
    ---------         | MUX   |   2   |      |
    |       |     2   |      0|--/------------
    | I2C-0 |----/----|       |   2
    |       |         |      1|--/------------
    ---------         | 0x70  |              |
                      ---------            ------
                                           |AT24|
                                           |    |
                                           |0x50|
                                           ------

Describing hardware in the traditional style isn't possible any more:


i2c at 3000 {
        #address-cells = <1>;
        #size-cells = <0>;
        cell-index = <0>;
        compatible = "fsl-i2c";
        reg = <0x3000 0x100>;
        interrupts = <43 2>;
        interrupt-parent = <&mpic>;
        dfsrr;

        mux at 70 { 
                #address-cells = <1>;
                #size-cells = <0>;
                compatible = "philips, pca9542";
                reg = <0x70>;

		/* and now the clients behind the multiplexer: */

                /* channel 0 */
                dtt at 48 {
                        compatible = "national, lm75";
                        reg = <0x48>;
                };	
                at24 at 50 {
                        compatible = "atmel, at24c08";
		        reg = <0x50>;
                };

                /* channel 1 */
                at24 at 50 {
                        compatible = "atmel, at24c08"; 
		        reg = <0x50>;
                };
        };
};

That can't work for reasons of naming and allocation. My proposal to
describe the hardware:

i2c at 3000 {
        #address-cells = <1>;
        #size-cells = <0>;
        cell-index = <0>;
        compatible = "fsl-i2c";
        reg = <0x3000 0x100>;
        interrupts = <43 2>;
        interrupt-parent = <&mpic>;
        dfsrr;

        mux at 70 { 
                #address-cells = <1>;
                #size-cells = <0>;
                compatible = "philips, pca9547";
                reg = <0x70>;
		
		/* and now the clients behind the multiplexer: */

                /* channel 0 */
                0-dtt at 48 {
                        mux-channel = <0>;
                        compatible = "national, lm75";
                        reg = <0x48>;
                }	
		0-at24 at 50 {
                        mux-channel = <0>;
                        compatible = "atmel, at24c08";
		        reg = <0x50>;
                }

                /* channel 1 */
                1-at24 at 50 {
                        mux-channel = <1>;
                        compatible = "atmel, at24c08";
		        reg = <0x50>;
                }
        }		
}

maybe that's absolute nonsense. I'd like to obtain other opinions and
suggestions.

Christian

Re: Device Tree configuration for I2C-Multiplexer and its Clients

[Grant Likely]

On Tue, Aug 18, 2009 at 2:31 AM, Herzig,
Christian<Christian.Herzig-SkAbAL50j+5BDgjK7y7TUQ@public.gmane.org> wrote:
> i2c at 3000 {
>        #address-cells = <1>;
>        #size-cells = <0>;
>        cell-index = <0>;
>        compatible = "fsl-i2c";
>        reg = <0x3000 0x100>;
>        interrupts = <43 2>;
>        interrupt-parent = <&mpic>;
>        dfsrr;
>
>        mux at 70 {
>                #address-cells = <1>;
>                #size-cells = <0>;
>                compatible = "philips, pca9542";
>                reg = <0x70>;
>
>                /* and now the clients behind the multiplexer: */
>
>                /* channel 0 */
>                dtt at 48 {
>                        compatible = "national, lm75";
>                        reg = <0x48>;
>                };
>                at24 at 50 {
>                        compatible = "atmel, at24c08";
>                        reg = <0x50>;
>                };
>
>                /* channel 1 */
>                at24 at 50 {
>                        compatible = "atmel, at24c08";
>                        reg = <0x50>;
>                };
>        };
> };
>
> That can't work for reasons of naming and allocation. My proposal to
> describe the hardware:

It looks to me like you should be using this form:

    mux@70 {
            #address-cells = <2>;   /* Note this change */
            #size-cells = <0>;
            compatible = "philips, pca9542";
            reg = <0x70>;

            /* and now the clients behind the multiplexer: */

            /* channel 0 */
            dtt@0,48 {
                    compatible = "national,lm75";
                    reg = < 0 0x48 >; /* now reg is specified with 2 cells */
            };
            at24@0,50 {
                    compatible = "atmel,at24c08";
                    reg = < 0 0x50 >;
            };

            /* channel 1 */
            at24@1,50 {
                    compatible = "atmel,at24c08";
                    reg = < 1 0x50 >;
            };
    };

RE: Device Tree configuration for I2C-Multiplexer and its Clients

[Herzig, Christian]

Hi Grant!

mux@70 {
        #address-cells = <2>;   /* Note this change */ /* I've noted ;-)
*/
        #size-cells = <0>;
        compatible = "philips, pca9542";
        reg = <0x70>;

        /* channel 0 */
        dtt@0,48 {
                compatible = "national,lm75";
                reg = < 0 0x48 >; /* now reg is specified with 2 cells
*/
        };
        at24@0,50 {
                compatible = "at24,24c08";
                reg = < 0 0x50 >;
        };
        /* channel 1 */
        at24@1,50 {
                compatible = "at24,24c08";
                reg = < 1 0x50 >;
        };
};

That looks very good to me!

Thank you very much, 
Christian