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[144.178.202.139]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ae3f6b08568sm1069884166b.139.2025.07.09.02.40.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 09 Jul 2025 02:40:43 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Wed, 09 Jul 2025 11:40:42 +0200 Message-Id: Cc: "Vinod Koul" , "Kishon Vijay Abraham I" , "Rob Herring" , "Krzysztof Kozlowski" , "Conor Dooley" , "Abel Vesa" , <~postmarketos/upstreaming@lists.sr.ht>, , , , , Subject: Re: [PATCH 1/4] dt-bindings: phy: qcom,snps-eusb2-repeater: Document qcom,tune-res-fsdif From: "Luca Weiss" To: "Luca Weiss" , "Krzysztof Kozlowski" X-Mailer: aerc 0.20.1-0-g2ecb8770224a-dirty References: <20250625-sm7635-eusb-repeater-v1-0-19d85541eb4c@fairphone.com> <20250625-sm7635-eusb-repeater-v1-1-19d85541eb4c@fairphone.com> <20250708-unicorn-of-ancient-excellence-e8945c@krzk-bin> <20250708-stoic-slim-bison-ac55ee@krzk-bin> In-Reply-To: Hi Krzysztof, On Tue Jul 8, 2025 at 10:31 AM CEST, Luca Weiss wrote: > On Tue Jul 8, 2025 at 10:21 AM CEST, Krzysztof Kozlowski wrote: >> On Tue, Jul 08, 2025 at 10:13:24AM +0200, Krzysztof Kozlowski wrote: >>> On Wed, Jun 25, 2025 at 11:14:56AM +0200, Luca Weiss wrote: >>> > Document the FS Differential TX Output Resistance Tuning value found = on >>> > the eUSB2 repeater on Qualcomm PMICs. >>> >=20 >>> > Signed-off-by: Luca Weiss >>> > --- >>> > Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml = | 6 ++++++ >>> > 1 file changed, 6 insertions(+) >>> >=20 >>> > diff --git a/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-re= peater.yaml b/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeate= r.yaml >>> > index 27f064a71c9fb8cb60e8333fb285f0510a4af94f..6bfd11657e29927359980= 63b3ca390e04a03930d 100644 >>> > --- a/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.= yaml >>> > +++ b/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.= yaml >>> > @@ -52,6 +52,12 @@ properties: >>> > minimum: 0 >>> > maximum: 7 >>> > =20 >>> > + qcom,tune-res-fsdif: >>> > + $ref: /schemas/types.yaml#/definitions/uint8 >>> > + description: FS Differential TX Output Resistance Tuning >>>=20 >>> Resistance is in Ohms, tuning could be in dB, so I wonder what are the >>> actual units here. Neither commit msg nor this description helps me to >>> understand that. >> >> I checked and the values are in Ohms. > > Yes it's Ohms but not 0x00 =3D 0 ohms, and it's also an offset in ohms > from the nominal value according to the Hardware Register Description I > have, e.g. 0x7 =3D -12.1ohm from the default > > I can try and create bindings using these Ohm offset values, I didn't > worry about it too much since the other tuning values in these bindings > are also just register values, presumably from before Konrad had access > to the docs. I've taken some more looks, and checked how similar tuning is handled in qcom,usb-snps-femto-v2.yaml and phy-qcom-snps-femto-v2.c, and changing up the concept of tuning in the eUSB2-repeater bindings+driver is not a trivial task. Since this is adding just one more property in-line with the already supported properties in the bindings+driver, can we get this in as-is, and deprecate all 4 qcom,tune-* properties later with a replacement that describes the values better? We have enough people at Qualcomm by now that should be able to do that, and have the required resources to answer any potential questions. Regards Luca