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Wed, 06 Jul 2022 07:35:18 -0700 (PDT) Message-ID: <27c99ecf-75ab-1798-2b59-3be397d153d0@linaro.org> Date: Wed, 6 Jul 2022 16:35:17 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH v1 08/16] arm64: dts: mt8195: Add power domains controller Content-Language: en-US To: Matthias Brugger , Tinghan Shen , Yong Wu , Joerg Roedel , Will Deacon , Rob Herring , Krzysztof Kozlowski , Chun-Jie Chen , AngeloGioacchino Del Regno , Enric Balletbo i Serra , Weiyi Lu References: <20220704100028.19932-1-tinghan.shen@mediatek.com> <20220704100028.19932-9-tinghan.shen@mediatek.com> <3b65405d-167f-a0c7-d15e-5da6f08d99b3@linaro.org> <17203a8a-407e-30cf-79de-352716c3ebce@gmail.com> From: Krzysztof Kozlowski In-Reply-To: <17203a8a-407e-30cf-79de-352716c3ebce@gmail.com> Cc: devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Project_Global_Chrome_Upstream_Group@mediatek.com, iommu@lists.linux-foundation.org, linux-mediatek@lists.infradead.org, linux-arm-kernel@lists.infradead.org X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On 06/07/2022 15:41, Matthias Brugger wrote: > > > On 04/07/2022 14:38, Krzysztof Kozlowski wrote: >> On 04/07/2022 12:00, Tinghan Shen wrote: >>> Add power domains controller node for mt8195. >>> >>> Signed-off-by: Weiyi Lu >>> Signed-off-by: Tinghan Shen >>> --- >>> arch/arm64/boot/dts/mediatek/mt8195.dtsi | 327 +++++++++++++++++++++++ >>> 1 file changed, 327 insertions(+) >>> >>> diff --git a/arch/arm64/boot/dts/mediatek/mt8195.dtsi b/arch/arm64/boot/dts/mediatek/mt8195.dtsi >>> index 8d59a7da3271..d52e140d9271 100644 >>> --- a/arch/arm64/boot/dts/mediatek/mt8195.dtsi >>> +++ b/arch/arm64/boot/dts/mediatek/mt8195.dtsi >>> @@ -10,6 +10,7 @@ >>> #include >>> #include >>> #include >>> +#include >>> >>> / { >>> compatible = "mediatek,mt8195"; >>> @@ -338,6 +339,332 @@ >>> #interrupt-cells = <2>; >>> }; >>> >>> + scpsys: syscon@10006000 { >>> + compatible = "syscon", "simple-mfd"; >> >> These compatibles cannot be alone. >> > > You mean we would need something like "mediatek,scpsys" as dummy compatible > that's not bound to any driver? Yes. syscon (and simple-mfd) must always come with a specific compatible. > >>> + reg = <0 0x10006000 0 0x1000>; >>> + #power-domain-cells = <1>; >> >> If it is simple MFD, then probably it is not a power domain provider. >> Decide. > > The SCPSYS IP block of MediaTek SoCs group several functionality, one is the > power domain controller. Others are not yet implemented, but defining the scpsys > as a MFD will give us the possibility to do so in the future. No, quite the opposite. Having simple-mfd prevents you from implementing it correctly later as a driver, because you cannot remove it. It would be ABI break. It's fine to have one block being a simple MFD having several children, but then it's not a power controller. Children could be such power controller, but not simple-mfd. Rob explained this several times: https://lore.kernel.org/all/YXhINE00HG6hbQI4@robh.at.kernel.org/ https://lore.kernel.org/all/20220701000959.GA3588170-robh@kernel.org/ Best regards, Krzysztof _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu