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[89.27.92.210]) by smtp.gmail.com with ESMTPSA id p17-20020a2ea4d1000000b0025d64453f4dsm2316547ljm.122.2022.08.23.04.02.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 23 Aug 2022 04:02:44 -0700 (PDT) Message-ID: Date: Tue, 23 Aug 2022 14:02:43 +0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.12.0 Subject: Re: [PATCH v2 2/4] arm64: dts: apple: t8103: Add MCA and its support Content-Language: en-US To: =?UTF-8?Q?Martin_Povi=c5=a1er?= Cc: Liam Girdwood , Mark Brown , Rob Herring , Krzysztof Kozlowski , Hector Martin , Sven Peter , Philipp Zabel , Alyssa Rosenzweig , asahi@lists.linux.dev, alsa-devel@alsa-project.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org References: <20220819125430.4920-1-povik+lin@cutebit.org> <20220819125430.4920-3-povik+lin@cutebit.org> <38094e2d-c75c-920b-4b4d-aa377971f615@linaro.org> From: Krzysztof Kozlowski In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On 19/08/2022 17:24, Martin Povišer wrote: > > >> On 19. 8. 2022, at 15:12, Krzysztof Kozlowski wrote: >> >> On 19/08/2022 15:54, Martin Povišer wrote: >>> Add the MCA I2S transceiver node and its supporting NCO, ADMAC nodes. >>> >>> Signed-off-by: Martin Povišer >>> --- >>> arch/arm64/boot/dts/apple/t8103.dtsi | 70 ++++++++++++++++++++++++++++ >>> 1 file changed, 70 insertions(+) >>> >>> diff --git a/arch/arm64/boot/dts/apple/t8103.dtsi b/arch/arm64/boot/dts/apple/t8103.dtsi >>> index 51a63b29d404..2dc3125aca5b 100644 >>> --- a/arch/arm64/boot/dts/apple/t8103.dtsi >>> +++ b/arch/arm64/boot/dts/apple/t8103.dtsi >>> @@ -532,6 +532,76 @@ port02: pci@2,0 { >>> <0 0 0 4 &port02 0 0 0 3>; >>> }; >>> }; >>> + >>> + dart_sio: iommu@235004000 { >>> + compatible = "apple,t8103-dart", "apple,dart"; >>> + reg = <0x2 0x35004000 0x0 0x4000>; >>> + interrupt-parent = <&aic>; >>> + interrupts = ; >>> + #iommu-cells = <1>; >>> + power-domains = <&ps_sio_cpu>; >>> + }; >>> + >>> + nco_clkref: clock-ref { >>> + compatible = "fixed-clock"; >>> + #clock-cells = <0>; >>> + clock-frequency = <900000000>; >>> + clock-output-names = "nco_ref"; >>> + }; >> >> Reference clocks are usually physically outside of SoC (e.g. on the >> board), so: >> 1. Not part of "soc" node. >> 2. It should be defined by board. At least clock-frequency should be there. > > Ah, right, this deserves commentary: Since this is a reverse-engineered > driver/platform support, we give up on knowing the clock tree exactly. Instead > we model the clock input to the Numerically Controlled Oscillator (‘nco’ node > below) with this fabulated fixed clock reference. > > I guess eventually the clock tree is rooted off the SoC, and there’s > nothing guaranteeing the same reference clock to the NCO across machines (being > function of the board wiring and the proprietary firmware). In the end I would > argue for keeping the ‘clock-ref’ here in ’soc' but have the clock-frequency > defined by board. Sounds reasonable? Yes. Best regards, Krzysztof