On Fri, Aug 30, 2024 at 10:19 PM Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote: > > On Fri, Aug 30, 2024 at 11:46:39AM +0800, Tyrone Ting wrote: > > Modify i2c frequency from table parameters > > for NPCM i2c modules. > > > > Supported frequencies are: > > > > 1. 100KHz > > 2. 400KHz > > 3. 1MHz > > There is no explanations "why". What's wrong with the calculations done in the > current code? > > -- > With Best Regards, > Andy Shevchenko > > Hi Andy, The original equations were tested on a variety of chips and base clocks. Since we added devices that use higher frequencies of the module we saw that there is a mismatch between the equation and the actual results on the bus itself, measured on scope. So instead of using the equations we did an optimization per module frequency, verified on a device. Most of the work was focused on the rise time of the SCL and SDA, which depends on external load of the bus and PU. We needed to make sure that in all valid range of load the rise time is compliant of the SMB spec timing requirements. This patch include the final values after extensive testing both at Nuvoton as well as at customer sites. BR, Tali Perry Nuvoton.
