>-----Original Message----- >From: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx> >Sent: Tuesday, July 5, 2022 8:29 AM >To: Han Xu <han.xu@xxxxxxx>; Bough Chen <haibo.chen@xxxxxxx>; >ashish.kumar@xxxxxxx; yogeshgaur.83@xxxxxxxxx; broonie@xxxxxxxxxx; >robh+dt@xxxxxxxxxx; krzysztof.kozlowski+dt@xxxxxxxxxx; >singh.kuldeep87k@xxxxxxxxx; tudor.ambarus@xxxxxxxxxxxxx; p.yadav@xxxxxx; >michael@xxxxxxxx; miquel.raynal@xxxxxxxxxxx; richard@xxxxxx; vigneshr@xxxxxx; >shawnguo@xxxxxxxxxx; s.hauer@xxxxxxxxxxxxxx; kernel@xxxxxxxxxxxxxx >Cc: linux-spi@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; >devicetree@xxxxxxxxxxxxxxx; linux-mtd@xxxxxxxxxxxxxxxxxxx; festevam@xxxxxxxxx; >dl-linux-imx <linux-imx@xxxxxxx>; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; >zhengxunli@xxxxxxxxxxx >Subject: Re: [PATCH 07/11] dt-bindings: spi: spi-nxp-fspi: add a new property >nxp,fspi-dll-slvdly > >On 05/07/2022 15:19, Han Xu wrote: >>>>>> + nxp,fspi-dll-slvdly: >>>>>> + $ref: /schemas/types.yaml#/definitions/uint32 >>>>>> + description: | >>>>>> + Specify the DLL slave line delay value. >>>>> >>>>> What are the units? >>>> >>>> Do you mean here need to give more detail explain about this properity? >>>> >>>> How about change like this? >>>> Specify the DLL slave line delay value. The delay target for slave delay line is: >>> ((nxp,fspi-dll-slvdly+1) * 1/32 * clock cycle of reference clock (serial root clock). >>> >>> This would be good. >>> >>>> The range of this value is 0~16. >>> >>> This needs to go to schema instead as "maximum: 16". >>> >>> But still the question is - what are the units used in this "delay"? ms? us? >> >> HI Krzysztof, >> >> According to the formula, the range should be 0~15, 16 should do nothing or no >delay. > >Sure, just add some constraint. > >> >> The unit should be clock phase. In other words, the delay can be in range of >1/32~1/2 clock cycle. > >So we probably misunderstood each other... looking at the driver it also explains >the confusing. You encoded here register value which is pretty often wrong >approach. > >This should be instead meaningful value for the user of the bindings, so usually >using one of property units: >https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com >%2Fdevicetree-org%2Fdt- >schema%2Fblob%2Fmain%2Fdtschema%2Fschemas%2Fproperty- >units.yaml&data=05%7C01%7Chan.xu%40nxp.com%7C0ffe3d706e064f14382 >108da5e8a5add%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C6379262 >45564450475%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV >2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=Q4 >SfVnBN%2BQ0vYKJzRf%2FXZkCA1WGyPV9doFcb%2BLSKx4w%3D&reserved=0 > >I think you could use here clock cycles or clock phase, but then it has to be obvious >it is that unit. Hi Krzysztof, Let me clarify it, in the document a term "delay cell" was used to descript this register bit. Each delay cell equals "1/32 clock phase", so the unit of delay cell is clock phase. The value user need set in DT just number to define how many delay cells needed. > >Best regards, >Krzysztof
