Messages in this thread | | | Date | Tue, 05 Jul 2022 16:06:02 +0200 | From | Michael Walle <> | Subject | Re: [PATCH 07/11] dt-bindings: spi: spi-nxp-fspi: add a new property nxp,fspi-dll-slvdly |
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Am 2022-07-05 16:00, schrieb Han Xu: >> -----Original Message----- >> From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> >> Sent: Tuesday, July 5, 2022 8:29 AM >> To: Han Xu <han.xu@nxp.com>; Bough Chen <haibo.chen@nxp.com>; >> ashish.kumar@nxp.com; yogeshgaur.83@gmail.com; broonie@kernel.org; >> robh+dt@kernel.org; krzysztof.kozlowski+dt@linaro.org; >> singh.kuldeep87k@gmail.com; tudor.ambarus@microchip.com; >> p.yadav@ti.com; >> michael@walle.cc; miquel.raynal@bootlin.com; richard@nod.at; >> vigneshr@ti.com; >> shawnguo@kernel.org; s.hauer@pengutronix.de; kernel@pengutronix.de >> Cc: linux-spi@vger.kernel.org; linux-kernel@vger.kernel.org; >> devicetree@vger.kernel.org; linux-mtd@lists.infradead.org; >> festevam@gmail.com; >> dl-linux-imx <linux-imx@nxp.com>; >> linux-arm-kernel@lists.infradead.org; >> zhengxunli@mxic.com.tw >> 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
Hm, you should fix your mail server.
>> >> 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.
Then should the unit be "-degrees" and the possible range 0-180?
-michael
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