Overlapping regions in DT

[Tsahee Zidenberg]

syscon regmap is one possible way to access a register file from two
different drivers without mapping it twice. But in that case you loose
the name-per-register in devicetree. The devtree maps the general
regfile, and the drivers know the offsets by themselves.
Have a look here:
Have a look: http://thread.gmane.org/gmane.linux.kernel/1352299

On 8 February 2015 at 05:17, Stefan Wahren <stefan.wahren at i2se.com> wrote:
> Hi,
>
> currently i work on two DT capable drivers for a ARM9 processor. The former
> driver mxs_power.c should trigger the population of the underlying power
> management functions and the ladder take care of the on-chip regulators. In the
> future more drivers
> should be added as child nodes of the power driver.
>
> My problem is that some of the processor registers are not separated per
> function. So
> the drivers need access (mostly read) on the same registers.
>
> Here are my questions:
>
> How should define i the register space in the device?
> Define the regions in the parent node and use offsets in the childs?
> Which functions are recommend for such access?
>
> I want to make use of of_platform_populate / of_platform_depopulate.
> Is there anything i should take care of?
>
> The relevant parts of the devicetree is at the end of the mail.
>
> Best regards
> Stefan
>
>        power: power at 80044000 {
>                 compatible = "fsl,imx28-power"; /* handled by mxs_power.c */
>                 #address-cells = <1>;
>                 #size-cells = <1>;
>                 reg = <0x80044000 0x2000>;
>                 interrupts = <6>;
>                 ranges;
>
>                 reg_vddd: regulator at 80044040 {
>                         reg = <0x80044040 0x10>,
>                               <0x80044010 0x10>,
>                               <0x800440c0 0x10>;
>                         reg-names = "base-address",
>                                     "v5ctrl-address",
>                                     "status-address";
>                         compatible = "fsl,imx28-vddd"; /* handled by
> mxs-regulator.c */
>                         regulator-name = "vddd";
>                         regulator-min-microvolt = <1350000>;
>                         regulator-max-microvolt = <1550000>;
>                         vddd-supply = <&reg_vdda>;
>                 };
>
>                 reg_vdda: regulator at 80044050 {
>                         reg = <0x80044050 0x10>,
>                               <0x80044010 0x10>,
>                               <0x800440c0 0x10>;
>                         reg-names = "base-address",
>                                     "v5ctrl-address",
>                                     "status-address";
>                         compatible = "fsl,imx28-vdda"; /* handled by
> mxs-regulator.c */
>                         regulator-name = "vdda";
>                         regulator-min-microvolt = <1725000>;
>                         regulator-max-microvolt = <1950000>;
>                         vdda-supply = <&reg_vddio>;
>                 };
>
>                 reg_vddio: regulator at 80044060 {
>                         reg = <0x80044060 0x10>,
>                               <0x80044010 0x10>,
>                               <0x800440c0 0x10>;
>                         reg-names = "base-address",
>                                     "v5ctrl-address",
>                                     "status-address";
>                         compatible = "fsl,imx28-vddio"; /* handled by
> mxs-regulator.c */
>                         regulator-name = "vddio";
>                         regulator-min-microvolt = <3000000>;
>                         regulator-max-microvolt = <3575000>;
>                         regulator-microvolt-offset = <80000>;
>                 };
>         };
>
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