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[188.155.181.108]) by smtp.gmail.com with ESMTPSA id el5sm10993751edb.71.2022.02.23.01.15.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 23 Feb 2022 01:15:37 -0800 (PST) Message-ID: <455a8a87-63e7-7864-f765-142be18d1fa8@canonical.com> Date: Wed, 23 Feb 2022 10:15:36 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [PATCH v2 09/15] scsi: ufs: deprecate 'freq-table-hz' property Content-Language: en-US To: Bjorn Andersson Cc: Alim Akhtar , Avri Altman , Rob Herring , Andy Gross , Wei Xu , Nishanth Menon , Vignesh Raghavendra , Tero Kristo , "James E.J. Bottomley" , "Martin K. Petersen" , Jan Kotas , Li Wei , Stanley Chu , Yaniv Gardi , linux-scsi@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-mediatek@lists.infradead.org References: <20220222145854.358646-1-krzysztof.kozlowski@canonical.com> <20220222145854.358646-10-krzysztof.kozlowski@canonical.com> From: Krzysztof Kozlowski In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On 22/02/2022 19:16, Bjorn Andersson wrote: > On Tue 22 Feb 06:58 PST 2022, Krzysztof Kozlowski wrote: > >> The 'freq-table-hz' is not correct in DT schema, because '-hz' suffix >> defines uint32 type, not an array. Therefore deprecate 'freq-table-hz' >> and use 'freq-table' instead. >> > > Patch looks good in itself, but why don't we use opp-table to describe > the performance states? > > In particular looking at the two columns of frequencies for various > Qualcomm boards they require different performance-states. > > A concrete example is sm8350.dtsi, which specifies 75MHz and 300MHz as > the first frequency pair. The lower level requires the VDD_CX power rail > to be at least &rpmhpd_opp_low_svs, the higher frequency has a > required-opps of &rpmhpd_opp_nom. > > > As this isn't possible to express in the current binding we've just been > forced to always run at a higher voltage level and kept this in the todo > list. > > But rather than migrating freq-table-hz to freq-table and then having to > introduce an opp table to express the power constraints, could we > perhaps skip the intermediate step? > > Or would you have any other suggestion about how we can represent the > required-opps level together with the freq-table (if that's what we want > to stick with). Usage of OPP tables is interesting solution. It would solve your problem of power rail levels. This would need several opp-tables - one for each clock, which is not a big problem. The problem is that I do not have any UFS hardware (none of my Samsung Exynos boards have UFS... I don't have even arm64 Exynos chips :( ), so implementing it theoretically will be painful. OTOH, I believe that having a working dtschema is very useful. Having dtschema without errors/warnings is even worth some churn/intermediary work. The intermediary work is also not that big. Once proper OPP is implemented, we will have "just" two deprecated properties in the bindings. Best regards, Krzysztof