linux-kernel - Re: [linux-sunxi] [PATCH 0/3] Add basic support for RTC on Allwinner H6 SoC

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Message-ID: <20190807105502.GK3600@piout.net>
Date:   Wed, 7 Aug 2019 12:55:02 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Chen-Yu Tsai <wens@...e.org>, Mark Rutland <mark.rutland@....com>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        devicetree <devicetree@...r.kernel.org>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-sunxi <linux-sunxi@...glegroups.com>,
        Rob Herring <robh+dt@...nel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-rtc@...r.kernel.org
Subject: Re: [linux-sunxi] [PATCH 0/3] Add basic support for RTC on Allwinner
 H6 SoC

Hi,

On 06/08/2019 20:30:45+0200, Ondřej Jirman wrote:
> Maybe whether XO or DCXO is used also matters if you want to do some fine
> tunning of DCXO (control register has pletny of options), but that's probably
> better done in u-boot. And there's still no need to read HOSC source from DT.
> The driver can just check compatible, and if it is H6 and OSC_CLK_SRC_SEL is 1,
> it can do it's DCXO tunning, or whatever. But neither OS nor bootloader will
> be using this info to gate/disable the osciallator.
> 

It is actually useful to be able to tweak the crystal tuning at
runtime to be able to reduce clock drift and compare with a reliable
source (e.g. NTP).
I'm curious, what kind of options does this RTC have?

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com