Russell,
On Sun, Dec 15, 2019 at 04:39:05PM +0000, Russell King wrote:
> The I2C specification states that tsu:sto for standard mode timing must
> be at minimum 4us. Pictographically, this is:
>
> SCL: ____/~~~~~~~~~
> SDA: _________/~~~~
> ->| |<- 4us minimum
>
> We are currently waiting 2.5us between asserting SCL and SDA, which is
> in violation of the standard. Adjust the timings to ensure that we meet
> what is stipulated as the minimum timings to ensure that all devices
> correctly interpret the STOP bus transition.
>
> This is more important than trying to generate a square wave with even
> duty cycle.
Ack.
> Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
> - /* Creating STOP again, see above */
Can we keep this comment, though? I think it still has value together
with the other comment above it.
> - ndelay(RECOVERY_NDELAY / 2);
> + if (scl) {
> + /* Honour minimum tsu:sto */
> + ndelay(RECOVERY_NDELAY);
> + } else {
> + /* Honour minimum tf and thd:dat */
> + ndelay(RECOVERY_NDELAY / 2);
> + }
Thanks,
Wolfram
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