[RFC PATCH] ARM: dts: ls1021a: add size-cells and address-cells to scfg and dcfg nodes

[RFC PATCH] ARM: dts: ls1021a: add size-cells and address-cells to scfg and dcfg nodes

[Rasmus Villemoes]

A single u32 is sufficient to specify a register in the Device
Configuration Unit/Supplemental Configuration Unit. Moreover, they only
consist of 32 bit registers (for the DCFG we even have "These registers
only support 32-bit accesses." according to the reference manual), so no
size specification is needed.

Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
---
None of the in-tree .dts files using ls1021a.dtsi currently define a
subnode of either node. It is possible, though somewhat unlikely, that
some out-of-tree .dts file is built against the in-tree ls1021a.dtsi,
and I don't know if such files are treated the same as out-of-tree
modules (i.e., they get to fix the breakage).

The reason I'm proposing to add these is that I'm about to add a subnode
of scfg with a reg property, and if possible I'd like to avoid the
somewhat clumsy

  reg = <0 0x1ac 0 4>;

when reg = <0x1ac>; would convey the same information. But if the
#address-cells and #size-cells properties are set in stone once the
.dtsi is in mainline, I'll just accept the clumsiness.

arch/arm/boot/dts/ls1021a.dtsi | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm/boot/dts/ls1021a.dtsi b/arch/arm/boot/dts/ls1021a.dtsi
index c31dad98f989..3c9fadcd611d 100644
--- a/arch/arm/boot/dts/ls1021a.dtsi
+++ b/arch/arm/boot/dts/ls1021a.dtsi
@@ -159,6 +159,8 @@
 		dcfg: dcfg@1ee0000 {
 			compatible = "fsl,ls1021a-dcfg", "syscon";
 			reg = <0x0 0x1ee0000 0x0 0x10000>;
+			#address-cells = <1>;
+			#size-cells = <0>;
 			big-endian;
 		};
 
@@ -202,6 +204,8 @@
 		scfg: scfg@1570000 {
 			compatible = "fsl,ls1021a-scfg", "syscon";
 			reg = <0x0 0x1570000 0x0 0x10000>;
+			#address-cells = <1>;
+			#size-cells = <0>;
 			big-endian;
 		};
 
-- 
2.15.1

Re: [RFC PATCH] ARM: dts: ls1021a: add size-cells and address-cells to scfg and dcfg nodes

[Rasmus Villemoes]

On 2018-02-23 14:31, Rasmus Villemoes wrote:
> A single u32 is sufficient to specify a register in the Device
> Configuration Unit/Supplemental Configuration Unit. Moreover, they only
> consist of 32 bit registers (for the DCFG we even have "These registers
> only support 32-bit accesses." according to the reference manual), so no
> size specification is needed.
> 
> Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
> ---
> None of the in-tree .dts files using ls1021a.dtsi currently define a
> subnode of either node. It is possible, though somewhat unlikely, that
> some out-of-tree .dts file is built against the in-tree ls1021a.dtsi,
> and I don't know if such files are treated the same as out-of-tree
> modules (i.e., they get to fix the breakage).
> 
> The reason I'm proposing to add these is that I'm about to add a subnode
> of scfg with a reg property, and if possible I'd like to avoid the
> somewhat clumsy
> 
>   reg = <0 0x1ac 0 4>;

Ah, apparently I've misunderstood how address-cells/size-cells worked; I
thought they would be taken from the nearest ancestor node specifying
them, so that 2/2 would apply to scfg. But it seems they have to be
present in the parent node itself, otherwise defaulting to 2/1. So the
above should be <0 0x1ac 4>, which is still clumsier than needed.

Rasmus