linux-kernel - Re: [PATCH V6 2/2] rtc: zynqmp: Add calibration set and get support

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Date:   Fri, 10 Jun 2022 12:12:11 +0200
From:   Peter Korsgaard <peter@...sgaard.com>
To:     "Neeli, Srinivas" <srinivas.neeli@....com>
Cc:     Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Srinivas Neeli <srinivas.neeli@...inx.com>,
        "a.zummo@...ertech.it" <a.zummo@...ertech.it>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "michal.simek@...inx.com" <michal.simek@...inx.com>,
        "sgoud@...inx.com" <sgoud@...inx.com>,
        "shubhraj@...inx.com" <shubhraj@...inx.com>,
        "neelisrinivas18@...il.com" <neelisrinivas18@...il.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-rtc@...r.kernel.org" <linux-rtc@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "git@...inx.com" <git@...inx.com>
Subject: Re: [PATCH V6 2/2] rtc: zynqmp: Add calibration set and get support

>>>>> "Neeli," == Neeli, Srinivas <srinivas.neeli@....com> writes:

Hi,

 >> >> 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.

Ok, great!

Please put this change in a separate commit from the get/set logic.

-- 
Bye, Peter Korsgaard