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:

quoted

quoted

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"?