On Mon, Apr 12, 2021 at 08:03:14PM +0800, Qii Wang wrote: > On Wed, 2021-04-07 at 20:19 +0200, Wolfram Sang wrote: > > > Due to clock stretch, our HW IP cannot meet the ac-timing > > > spec(tSU;STA,tSU;STO). > > > There isn't a same delay for clock stretching, so we need pass a > > > parameter which can be found through measurement to meet most > > > conditions. > > > > What about using this existing binding? > > > > - i2c-scl-internal-delay-ns > > Number of nanoseconds the IP core additionally needs to setup SCL. > > > > I can't see the relationship between "i2c-scl-falling-time-ns" and clock > stretching, is there a parameter related to clock stretching? ( you wrote "i2c-scl-falling-time-ns" above, didn't you mean "i2c-scl-internal-delay-ns" instead? ) Not yet, and I wonder if there can be one. In I2C (not SMBus), devices are allowed to stretch the clock as long as they want, so what should be specified here? I suggesteed "internal-delay" because AFAIU your hardware needs this delay to be able to cope with clock stretching. > If you think both of them will affect the ac-timing of SCL, at this > point, "i2c-scl-falling-time-ns" maybe a good choice. Do you mean "i2c-scl-falling-time-ns" or "i2c-scl-internal-delay-ns"?
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