Hi Krzystof, thank you for your explanations. As I'm still quite new to writing bindings, I still have some questions: On Fri, 2023-04-07 at 11:03 +0200, Krzysztof Kozlowski wrote: > On 05/04/2023 14:14, Johannes Zink wrote: > > Hi Krysztof, > > > > thanks for your review, please find my questions below. > > > > On Wed, 2023-04-05 at 13:51 +0200, Krzysztof Kozlowski wrote: > > > [snip] > > > > A phandle to the regulator for USB VBUS. > > > > > > > > + fsl,phy-tx-vref-tune: > > > > + description: > > > > + HS DC Voltage level adjustment > > > > > > "Level" in what units? > > > > > > > The datasheet just shows percent, ranging from -6 to +24%, in 2% > > increments. What unit would you suggest? > > percent > https://github.com/devicetree-org/dt-schema/blob/main/dtschema/schemas/property-units.yaml I am still a bit confused how to use this properly. How can I restrict the values to multiples of 2 in order to avoid illegal values? At the moment the only thing I could come up with is something like fsl,phy-tx-vref-tune-percent: description: | Adjusts the high-speed DC level voltage $ref: /schemas/types.yaml#/definitions/int32 minimum: -6 maximum: 24 default: 0 Does something like this work? I am not quite sure if I am on the right track here, especially as this requires a signed int, of which I have not seen many examples so far. Also, as far as the description is concerned: This is almost the entire information I there is in the datasheet. As I try to upstream some of the vendor downstream patches, I do not have any additional information. > > > > > > > + $ref: /schemas/types.yaml#/definitions/uint32 > > > > + enum: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, > > > > 15, > > > > 16] > > > > + > > > > + fsl,phy-tx-rise-tune: > > > > + description: > > > > + HS Transmitter Rise/Fall Time Adjustment > > > > + $ref: /schemas/types.yaml#/definitions/uint32 > > > > + enum: [0, 1, 2, 3] > > > > + > > > > + fsl,phy-tx-preemp-amp-tune: > > > > + description: > > > > + HS Transmitter Pre-Emphasis Current Control > > > > > > If this is current then use standard unit suffixes. > > > > According to the datasheet this is in "unit amonts" of 600uA, > > basically > > 0x600uA, 1x600uA etc. Should I just suffix it with uA then? > > Yes > > https://github.com/devicetree-org/dt-schema/blob/main/dtschema/schemas/property-units.yaml > > The register values can work sometimes fine but also do not scale at > all. For any other variant all the meanings will differ. Any other > IMX8 > phy will need new bindings and new description/values for your > register-like-fields. I think this particular property should work, probably its something like fsl,phy-tx-preemp-amp-tune-microamps: description: | Transmitter Pre-Emphasis Current Control Controls the amount of current sourced to DPn and DMn after a J-to- K or K-to-J transition. $ref: /schemas/types.yaml#/definitions/uint32 minimum: 0 maximum: 1800 default: 0 What's the right way to communicate that the value is in multiples of 600uA and that this is only an approximate Value? Add some free-text to the description? For some other properties, such as fsl,phy-pcs-tx-swing-full or fsl,phy-pcs-tx-deemph-3p5db the datasheet provides no information at all, neither on the unit nor on a valid range. What is the proper way for something like them (I try to get some of the freescale downstream patches to mainline, but they did not even provide bindings for their driver...) For fsl,phy-comp-dis-tune-percent, the actual values to not map well to integer amount of percent, but I have not found a permill in property- units. Also, as the steps appear quite arbitrary large, what is the correct way of restricting the values to valid values that the hardware can actually support? As reference, I have only seen stuff like the st,trim-hs-current in Documentation/devicetree/bindings/phy/phy-stm32- usbphyc.yaml so far... Thanks for helping me and best regards Johannes > > Best regards, > Krzysztof > > > -- Pengutronix e.K. | Johannes Zink | Steuerwalder Str. 21 | https://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686| Fax: +49-5121-206917-5555 |
