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[188.155.174.239]) by smtp.googlemail.com with ESMTPSA id a102-20020a509eef000000b0041614c8f79asm7552126edf.88.2022.03.14.00.39.57 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 14 Mar 2022 00:39:58 -0700 (PDT) Message-ID: Date: Mon, 14 Mar 2022 08:39:57 +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 1/3] dt-bindings: phy: qcom,usb-snps-femto-v2: Add phy override params bindings Content-Language: en-US To: Pavan Kondeti Cc: Sandeep Maheswaram , Rob Herring , Andy Gross , Bjorn Andersson , Kishon Vijay Abraham I , Vinod Koul , Greg Kroah-Hartman , Wesley Cheng , Stephen Boyd , Doug Anderson , Matthias Kaehlcke , devicetree@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-phy@lists.infradead.org, linux-usb@vger.kernel.org, quic_ppratap@quicinc.com, quic_kriskura@quicinc.com References: <1646288011-32242-1-git-send-email-quic_c_sanm@quicinc.com> <1646288011-32242-2-git-send-email-quic_c_sanm@quicinc.com> <20220314032952.GA27561@hu-pkondeti-hyd.qualcomm.com> From: Krzysztof Kozlowski In-Reply-To: <20220314032952.GA27561@hu-pkondeti-hyd.qualcomm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On 14/03/2022 04:29, Pavan Kondeti wrote: > Hi Krzysztof, > > On Thu, Mar 03, 2022 at 04:59:22PM +0100, Krzysztof Kozlowski wrote: >> On 03/03/2022 07:13, Sandeep Maheswaram wrote: >>> Add device tree bindings for SNPS phy tuning parameters. >>> >>> Signed-off-by: Sandeep Maheswaram >>> --- >>> .../bindings/phy/qcom,usb-snps-femto-v2.yaml | 125 +++++++++++++++++++++ >>> 1 file changed, 125 insertions(+) >>> >>> diff --git a/Documentation/devicetree/bindings/phy/qcom,usb-snps-femto-v2.yaml b/Documentation/devicetree/bindings/phy/qcom,usb-snps-femto-v2.yaml >>> index 0dfe691..227c097 100644 >>> --- a/Documentation/devicetree/bindings/phy/qcom,usb-snps-femto-v2.yaml >>> +++ b/Documentation/devicetree/bindings/phy/qcom,usb-snps-femto-v2.yaml >>> @@ -50,6 +50,131 @@ properties: >>> vdda33-supply: >>> description: phandle to the regulator 3.3V supply node. >>> >>> + qcom,hs-disconnect: >>> + $ref: /schemas/types.yaml#/definitions/uint32 >>> + description: >>> + This adjusts the voltage level for the threshold used to >>> + detect a disconnect event at the host. Possible values are. >> >> ':', instead of full stop. >> >>> + 7 -> +21.56% >>> + 6 -> +17.43% >>> + 5 -> +13.32% >>> + 4 -> +9.73% >>> + 3 -> +6.3 >>> + 2 -> +3.17% >>> + 1 -> 0, Design default% >> >> Use "default:" instead. Here and in other places. >> >>> + 0 -> -2.72% >> >> In current form this should be an enum... but actually current form is >> wrong. You should not store register values in DT. What if next version >> of hardware has a different meaning of these values? >> >> Instead, you should store here meaningful values, not register values. >> > > Thanks for the feedback. > > The values in % really makes the tuning easy. People look at the eye diagram > and decided whether to increase/decrease the margin. The absolute values > may not be that useful. All we need is an "adjustment" here. The databook > it self does not give any absolute values. > > I agree to the "enum" suggestion which we have been following for the > qusb2 driver already. > > The values have not changed in the last 5 years for this hardware block, so > defining enums for the % values would be really helpful. I did not say you cannot store here percentages. Quite opposite - store here the percentages. Just do not store register value. No. Please read my comment again - meaningful values are needed. Best regards, Krzysztof