On 12/03/2023 14:19, Andi Shyti wrote: > The I2C specification allows for the clock line to be held low > for a specified timeout to force the slave device into a 'wait' > mode. This feature is known as 'Clock stretching' and is > optional. > > In the NXP I2C specification, clock stretching is described as > the process of pausing a transaction by holding the SCL line LOW. > The transaction can only continue when the line is released HIGH > again.[*] However, most target devices do not include an SCL > driver and are therefore unable to stretch the clock. > > Add the following properties: > > - i2c-scl-clk-low-timeout-ms: This property specifies the > duration, in milliseconds, for which the clock is kept low and > a client needs to detect a forced waiting state. > > - i2c-scl-has-clk-low-timeout: This property specifies whether > the I2C controller implements the clock stretching property. > > It's important to note that this feature should not be confused > with the SMBUS clock timeout, which serves a similar function but > specifies a timeout of 25-35ms. The I2C specification does not > recommend any specific timeout. > > [*] NXP, UM10204 - I2C-bus specification and user manual > Rev. 7.0, 1 October 2021, chapter 3.1.9. > > Signed-off-by: Andi Shyti <andi.shyti@xxxxxxxxxx> > --- > Documentation/devicetree/bindings/i2c/i2c.txt | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/Documentation/devicetree/bindings/i2c/i2c.txt b/Documentation/devicetree/bindings/i2c/i2c.txt > index fc3dd7ec0445..12c311f0e831 100644 > --- a/Documentation/devicetree/bindings/i2c/i2c.txt > +++ b/Documentation/devicetree/bindings/i2c/i2c.txt Although the properties are still sometimes added here, but the bindings are now in dtschema, so rather this should be updated: https://github.com/devicetree-org/dt-schema/blob/main/dtschema/schemas/i2c/i2c-controller.yaml > @@ -45,6 +45,15 @@ wants to support one of the below features, it should adapt these bindings. > Number of nanoseconds the SCL signal takes to rise; t(r) in the I2C > specification. > > +- i2c-scl-clk-low-timeout-ms > + Number of miliseconds the clock line needs to be pulled down in order > + to force a waiting state. > + > +- i2c-scl-has-clk-low-timeout > + Boolean value that indicates whether the controller implements the > + feature of wait induction through SCL low, with the timeout being > + implemented internally by the controller. > + > - i2c-sda-falling-time-ns > Number of nanoseconds the SDA signal takes to fall; t(f) in the I2C > specification. Best regards, Krzysztof
