Re: [PATCH v3 03/11] arm64: dts: mt8195: Add SCP core 1 node

[AngeloGioacchino Del Regno]

Il 17/01/23 09:19, TingHan Shen (沈廷翰) ha scritto:
> On Tue, 2022-09-27 at 13:01 +0200, AngeloGioacchino Del Regno wrote:
> > Il 27/09/22 04:55, Tinghan Shen ha scritto:
> > > Add the 2nd core(core 1) of MT8195 dual-core SCP to devicetree file.
> > > Reserve some SRAM spaces for the core 1 image.
> > >
> > > Signed-off-by: Tinghan Shen <tinghan.shen@xxxxxxxxxxxx>
> > > ---
> > >    arch/arm64/boot/dts/mediatek/mt8195.dtsi | 14 +++++++++++++-
> > >    1 file changed, 13 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/arch/arm64/boot/dts/mediatek/mt8195.dtsi b/arch/arm64/boot/dts/mediatek/mt8195.dtsi
> > > index 905d1a90b406..48d457bd39b8 100644
> > > --- a/arch/arm64/boot/dts/mediatek/mt8195.dtsi
> > > +++ b/arch/arm64/boot/dts/mediatek/mt8195.dtsi
> > > @@ -760,12 +760,24 @@
> > >    
> > >    		scp: scp@10500000 {
> > >    			compatible = "mediatek,mt8195-scp";
> > > -			reg = <0 0x10500000 0 0x100000>,
> > > +			reg = <0 0x10500000 0 0xa0000>,
> > >    			      <0 0x10720000 0 0xe0000>,
> > >    			      <0 0x10700000 0 0x8000>;
> > >    			reg-names = "sram", "cfg", "l1tcm";
> > >    			interrupts = <GIC_SPI 462 IRQ_TYPE_LEVEL_HIGH 0>;
> > >    			status = "disabled";
> > > +
> > > +			#address-cells = <1>;
> > > +			#size-cells = <1>;
> > > +			ranges = <0x105a0000 0 0x105a0000 0x20000>;
> > > +
> > > +			scp_c1: scp-c1@105a0000 {
> > > +				compatible = "mediatek,mt8195-scp-core";
> > > +				reg = <0x105a0000 0x20000>;
> > > +				reg-names = "sram";
> > > +				interrupts = <GIC_SPI 463 IRQ_TYPE_LEVEL_HIGH 0>;
> > > +				status = "disabled";
> > > +			};
> >
> > I think that the best way of describing a dual-core SCP in devicetree would
> > be either something like:
> >
> > scp: scp@10500000 {
> > 	compatible = "mediatek,mt8195-scp";
> > 	reg = <0 0x10500000 0 0xa0000>, <0 0x105a0000 0 0x20000>,
> > 	      <0 0x10720000 0 0xe0000>, <0 0x10700000 0 0x8000>;
> > 	reg-names = "sram", "sram-c1", "cfg", "l1tcm";
> > 	interrupts = <GIC_SPI 462 IRQ_TYPE_LEVEL_HIGH 0>,
> > 		     <GIC_SPI 463 IRQ_TYPE_LEVEL_HIGH 0>;
> > 	status = "disabled";
> > };
> >
> > ...but that may pose an issue when trying to assign different (or more instances
> > of the same) subnode(s) to each core... for which, I'd be more for something like:
> >
> > scp: scp@10500000 {
> > 	compatible = "mediatek,mt8195-scp";
> > 	reg = <0 0x10720000 0 0xe0000>, <0 0x10700000 0 0x8000>;
> > 	reg-names = "cfg", "l1tcm";
> > 	#address-cells = <1>;
> > 	#size-cells = <1>;
> > 	ranges = <0 0 0x10500000 0x100000>;
> > 	status = "disabled";
> >
> > 	scp_c0: scp-core@0 {
> > 		compatible = "mediatek,mt8195-scp-core";
> > 		reg = <0x0 0xa0000>;
> > 		reg-names = "sram";
> > 		interrupts = <GIC_SPI 462 IRQ_TYPE_LEVEL_HIGH 0>;
> > 	};
> >
> > 	scp_c1: scp-core@a0000 {
> > 		compatible = "mediatek,mt8195-scp-core";
> > 		reg = <0xa0000 0x20000>;
> > 		reg-names = "sram";
> > 		interrupts = <GIC_SPI 463 IRQ_TYPE_LEVEL_HIGH 0>;
> > 	};
> > };
> >
> > Regards,
> > Angelo
> Hi Angelo,
>
> I'm thinking about identifying the cores by the order of the sub nodes,
> i.e. core 0 must be the first sub node and core 1 must be the second sub node,
> because the scp cores in the example have the same compatible name.
>
> I'm hesitant to make the sub nodes appear in a certain order. Is it appropriate?
> Or, would it be more readable to create a new core id property? Or utilizing
> different compatble strings for cores? I would appreciat it if you could share your opinion.

Assuming that in a future >2 cores architecture only the first core, which I will
call "core 0" for commodity, will have "special treatment" and core 1, 2, 3...N
will always be "interchangeable", I think that something like `mediatek,scp-leader`
would work to identify the first core.

Cheers!
Angelo