How do I figure the I2C timings for a peripheral?
This is not something you'd typically need to adjust away from defaults.
In ordinary open-drain operation rise time would be governed by the pullup resistor chosen and bus capacitance.  You basically would not be able to make it &quot;too fast&quot; without requiring excessive drive down current, so really would just need to check that the rise time isn't approaching the maximum.  If it is you may need smaller resistors, within reason.  Should you find you need to a pullup firmer than say 2K2 to get a reasonable rise time, you probably have something wrong with the bus - often you can use at least twice that resistance if not more.
The fall time would depend on the strength of the drive, and is limited by physics.  Trying to achieve very short fall times is both pointless given the slow clock speed to be used, and perhaps counterproductive as hard edges could lead to the device being a source of radio interference extending to higher frequencies.