On 09/07/2025 14:22, Luca Weiss wrote: > On Wed Jul 9, 2025 at 12:16 PM CEST, Krzysztof Kozlowski wrote: >> On 09/07/2025 11:40, Luca Weiss wrote: >>> 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. >>>>>>> >>>>>>> Signed-off-by: Luca Weiss <luca.we...@fairphone.com> >>>>>>> --- >>>>>>> Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml | >>>>>>> 6 ++++++ >>>>>>> 1 file changed, 6 insertions(+) >>>>>>> >>>>>>> diff --git >>>>>>> a/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml >>>>>>> b/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml >>>>>>> index >>>>>>> 27f064a71c9fb8cb60e8333fb285f0510a4af94f..6bfd11657e2992735998063b3ca390e04a03930d >>>>>>> 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 >>>>>>> >>>>>>> + qcom,tune-res-fsdif: >>>>>>> + $ref: /schemas/types.yaml#/definitions/uint8 >>>>>>> + description: FS Differential TX Output Resistance Tuning >>>>>> >>>>>> 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 = 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 = -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? >> >> This is a new property, so other existing properties do not matter here. >> We cannot take new code which you already think should be deprecated. >> >> register-like values are acceptable for vendor properties, but that does >> not make them usually more readable. The question is whether this should >> be more readable for hardware engineers or anyone writing/validating >> DTS. Is the actual resistance important or no one ever cares because you >> paste whatever qcom told you and you do not know what should be actually >> there? >> >> I can imagine the first - that some document explains you should have >> resistance of foo because of bar, which would mean the property should >> be more readable. But I can also imagine the second. Make your claim in >> commit msg. > > Would this text in the commit message work for you? > > --- > Document the FS Differential TX Output Resistance Tuning value found on > the eUSB2 repeater on Qualcomm PMICs. The tuning values have special > meanings, being different offsets of the resistance to the default value > in Ohms but the exact meaning is not relevant here, as the correct > tuning is determined by hardware engineers to make sure the electrical > properties are as expected. > --- > > I'm trying to avoid resending the whole series if we're not yet aligned > on the wording. Sounds fine.
Best regards, Krzysztof
