[AMD Official Use Only - General] Hi, > -----Original Message----- > From: Peter Korsgaard <peter@xxxxxxxxxxxxx> > Sent: Thursday, June 9, 2022 8:30 PM > To: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx> > Cc: Srinivas Neeli <srinivas.neeli@xxxxxxxxxx>; a.zummo@xxxxxxxxxxxx; > robh+dt@xxxxxxxxxx; krzysztof.kozlowski+dt@xxxxxxxxxx; > michal.simek@xxxxxxxxxx; sgoud@xxxxxxxxxx; shubhraj@xxxxxxxxxx; Neeli, > Srinivas <srinivas.neeli@xxxxxxx>; neelisrinivas18@xxxxxxxxx; > devicetree@xxxxxxxxxxxxxxx; linux-rtc@xxxxxxxxxxxxxxx; linux-arm- > kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; git@xxxxxxxxxx > Subject: Re: [PATCH V6 2/2] rtc: zynqmp: Add calibration set and get support > > >>>>> "Alexandre" == Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx> > writes: > > > On 09/06/2022 16:50:03+0200, Peter Korsgaard wrote: > >> >>>>> "Srinivas" == Srinivas Neeli <srinivas.neeli@xxxxxxxxxx> writes: > >> > >> > Zynqmp RTC controller has a calibration feature to compensate >> > > time deviation due to input clock inaccuracy. > >> > Set and get calibration API's are used for setting and getting >> > > calibration value from the controller calibration register. > >> > As per RTC spec default calibration value is 0x7FFF. > >> > >> Where do you see that? ug1085 rev2.2 still lists: > >> > >> Programming Sequences > >> init rtc > >> 1. Write the value 0019_8231h into the calibration register, CALIB_WRITE. > >> > > > This is a very weird value. Last time I had a look, I couldn't find an > > explanation for it. > > Agreed. I am not arguing that it is sensible, I just wondered where this new > value comes from? > This information is missing in our TRM, as per the internal RTC IP design specification document, the calibration value should be crystal clock frequency minus one. For a crystal oscillator of 32.768KHz(0x8000) frequency, the calibration value will be 0x7FFF. Will update TRM with the required information. > -- > Bye, Peter Korsgaard
