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[72.83.177.149]) by smtp.gmail.com with ESMTPSA id cj24-20020a05622a259800b00399fe4aac3esm6540268qtb.50.2022.10.20.10.59.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 20 Oct 2022 10:59:42 -0700 (PDT) Message-ID: <835d3432-daf2-e824-5c84-7d47604f586f@linaro.org> Date: Thu, 20 Oct 2022 13:59:40 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.0 Subject: Re: [PATCH v2 2/3] arm64: dts: qcom: Add base QDU1000/QRU1000 DTSIs Content-Language: en-US To: Stephan Gerhold Cc: Melody Olvera , Andy Gross , Bjorn Andersson , Rob Herring , Krzysztof Kozlowski , linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org References: <20221014221138.7552-1-quic_molvera@quicinc.com> <20221014221138.7552-3-quic_molvera@quicinc.com> <56af2a04-1b21-000d-e3f9-86b6ac74aaf2@linaro.org> <50372a15-56ce-6ad6-f622-00624b909db8@linaro.org> <9fbe1bf5-a84d-c56b-1c0e-6848ee3d30fe@linaro.org> From: Krzysztof Kozlowski In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On 20/10/2022 13:18, Stephan Gerhold wrote: >> No, it puts attention to the board designer that he needs to provide the >> clock in his design. >> >> We had such talks about other platforms, although I do not have any >> recent bookmarks. Something older: >> >> https://lore.kernel.org/all/3382034.5ADO0F7naY@wuerfel/ >> >> https://lore.kernel.org/linux-samsung-soc/53DAB0A6.9030700@gmail.com/ >> > > If I understand you correctly your argument for having the clock in the > board DTS instead of the SoC DTSI is: > > The SoC DTSI describes the components of the SoC, while the board DTS > describes the components of the board (built around the SoC). The clock > is part of the board (and not the SoC) and therefore belongs into the > board DTS and not the SoC DTSI. Having the SoC/board components clearly > separated ensures people writing new board DTS pay attention to > everything board-specific. > > Correct? This sounds reasonable to me. Yes. > > However, the main question of my previous mail was: Why do you > alternatively recommend to keep the clock defined in the SoC DTSI and to > just put the clock-frequency into the board DTS? This sounds like a > contradiction of the above to me: the clock is still (partially) > described as part of the SoC, even though it belongs to the board. The proposal is a trade-off, compromise between code duplication and above recommendation of splitting SoC <-> board. As you said, all boards will provide this clock, so it is reasonable to put some pieces of it in the SoC DTSI to avoid duplication. But the final piece - what clock is there exactly (model, frequency etc) should be put in board DTS to clarify that this comes with board. > Someone writing a board DTS should not just put attention to the > clock-frequency, but also if they have a single fixed-clock or > maybe some kind of clock-fixed-factor setup, as I wrote. True. If such setup is probably, then my recommendation would be to put entire clock to the board. Just note, that even in proposed frequency->board DTS, it is still possible to use the clock-fixed-factor. Best regards, Krzysztof