> -----Original Message----- > From: Johannes Zink <j.zink@xxxxxxxxxxxxxx> > Sent: Tuesday, April 11, 2023 10:23 PM > To: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>; > vkoul@xxxxxxxxxx; kishon@xxxxxxxxxx; shawnguo@xxxxxxxxxx; > s.hauer@xxxxxxxxxxxxxx; kernel@xxxxxxxxxxxxxx; festevam@xxxxxxxxx; > dl-linux-imx <linux-imx@xxxxxxx>; robh+dt@xxxxxxxxxx; > krzysztof.kozlowski+dt@xxxxxxxxxx; Jun Li <jun.li@xxxxxxx>; Bough Chen > <haibo.chen@xxxxxxx>; linux-phy@xxxxxxxxxxxxxxxxxxx; > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > devicetree@xxxxxxxxxxxxxxx > Subject: Re: [PATCH 1/2] dt-bindings: phy: imx8mq-usb: add phy tuning > properties > > 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://gith/ > > > ub.com%2Fdevicetree-org%2Fdt-schema%2Fblob%2Fmain%2Fdtschema%2Fschemas > > %2Fproperty-units.yaml&data=05%7C01%7Cjun.li%40nxp.com%7Ca2e1e5bb6a78 > 4 > > > de5941d08db3a9847d0%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C63816 > > > 8197947407580%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2lu > > > MzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=kY4dXkOHRs9k% > > 2BeUQ5iixLYsNC8UotIgq6eOPGjbf01o%3D&reserved=0 > > 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://gith/ > > > ub.com%2Fdevicetree-org%2Fdt-schema%2Fblob%2Fmain%2Fdtschema%2Fschemas > > %2Fproperty-units.yaml&data=05%7C01%7Cjun.li%40nxp.com%7Ca2e1e5bb6a78 > 4 > > > de5941d08db3a9847d0%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C63816 > > > 8197947407580%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2lu > > > MzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=kY4dXkOHRs9k% > > 2BeUQ5iixLYsNC8UotIgq6eOPGjbf01o%3D&reserved=0 > > > > 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...) I will check with internal design team for those not well documented properties. Li Jun > > > 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.p/ > engutronix.de%2F&data=05%7C01%7Cjun.li%40nxp.com%7Ca2e1e5bb6a784de5941d > 08db3a9847d0%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C6381681979474 > 07580%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBT > iI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=Dq06I6tprUib5nOmp4pDFdY > MgYULn8MLj5iHwVlQHMY%3D&reserved=0 | > 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | > Amtsgericht Hildesheim, HRA 2686| Fax: +49-5121-206917-5555 |
