Hi Andy: Thank you for your comments. Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> 於 2024年10月1日 週二 下午9:23寫道： > > On Tue, Oct 01, 2024 at 02:28:54PM +0800, Tyrone Ting wrote: > > From: Tyrone Ting <kfting@xxxxxxxxxxx> > > > > Modify i2c frequency from table parameters > > for NPCM i2c modules. > > This two lines have a too small wrapping limit. > I'll make the statement in one line. > > Supported frequencies are: > > > > 1. 100KHz > > 2. 400KHz > > 3. 1MHz > > > > 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. > > > > Meanwhile, the equations were not accurate to begin with. > > They are an approximation of the ideal value. The ideal value is > > calculated per frequency of the core module. > > > > 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. > > > > Different PCB designs, or specifically to this case: the number > > and type of targets on the bus, impact the required values for > > the timing registers. > > > > Users can recalculate the numbers for each bus and get an even better > > optimization, but our users chose not to. > > > > We manually picked values per frequency that match the entire valid > > range of targets (from 1 to max number). Then we check against the > > AMR described in SMB spec and make sure that none of the values > > is exceeding. > > > > This process was led by the chip architect and included a lot of testing. > > Personally I consider table approach is not so flexible and it is definitely > does not scale (in the result — hard to maintain for all customers), but if > it's hard to calculate all necessary data and there are other pros of it, > I'm fine. > > TL;DR: I don't like this patch, but I don't want to stop you, hence no tags > from me. > > -- > With Best Regards, > Andy Shevchenko > > Thank you again. Regards, Tyrone
