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

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Message-ID: <a2fd85fd-c325-043b-a6d5-10969c4eb34b@collabora.com>
Date:   Tue, 17 Jan 2023 09:55:55 +0100
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     TingHan Shen (沈廷翰) 
        <TingHan.Shen@...iatek.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        Tiffany Lin (林慧珊) 
        <tiffany.lin@...iatek.com>,
        "mchehab@...nel.org" <mchehab@...nel.org>,
        Yunfei Dong (董云飞) 
        <Yunfei.Dong@...iatek.com>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "andersson@...nel.org" <andersson@...nel.org>,
        Andrew-CT Chen (陳智迪) 
        <Andrew-CT.Chen@...iatek.com>,
        "mathieu.poirier@...aro.org" <mathieu.poirier@...aro.org>
Cc:     "linux-remoteproc@...r.kernel.org" <linux-remoteproc@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v3 03/11] arm64: dts: mt8195: Add SCP core 1 node

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@...iatek.com>
>>> ---
>>>    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@...00000 {
>>>    			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@...a0000 {
>>> +				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@...00000 {
>> 	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@...00000 {
>> 	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@...00 {
>> 		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