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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-mtd" Errors-To: linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org On 22/07/05 05:38PM, Krzysztof Kozlowski wrote: > On 05/07/2022 16:52, Han Xu wrote: > > On 22/07/05 04:12PM, Krzysztof Kozlowski wrote: > >> On 05/07/2022 16:06, Michael Walle wrote: > >>> > >>>>> > >>>>> 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? > >> > >> Thanks. We don't have it documented currently, but the unit seems > >> reasonable. > > > > IMO, use the unit "-degrees" makes it more complicate. Personaly I would > > calculate how many clock cycle delay needed, such as 1/4 clock cycle or half > > clock cycle. Using degree brings extra calculation. > > And what if the next device uses a bit different divider? Like 1/16? > This is why we have standard units so people won't push register values > into the bindings. > > > > > The granularity of the clock phase change is 1/32 of 180 degree, but the range > > 0-180 make people feel it can be set in any degree in range. > > Yes, because that's how the bindings are being written - allowing any > reasonable value, not register-specific value, to be used because it is > the most flexible, hardware-independent and allows further customization > of bindings (e.g. new devices). Embedding device programming model into > the bindings contradicts it. > > Second, nothing stops you from narrowing the acceptable values with an > enum. This still allows extension. Your 1/32 does not. > > > > > If I describe all details of the relation between "nxp,fspi-dll-slvdly" and > > "delay cell" in patch v2, do you think it's clear for users? > > 1/32 could be a nice unit, but degrees is better. Just like uV is better > than 1/32 of V. Like 1 us is better than 1/32 of ms. > > Do you see in the bindings many other values like time, potential, > current or power described in 1/32 units? That make sense. I will use degree as the unit and round to register proper value in driver as Michael suggested. Thanks for all comments. > > Best regards, > Krzysztof ______________________________________________________ Linux MTD discussion mailing list http://lists.infradead.org/mailman/listinfo/linux-mtd/