linux-kernel - Re: [PATCH v2] RTC: RK808: Work around hardware bug on November 31st

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Date:	Thu, 10 Dec 2015 19:41:19 +0100
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Julius Werner <jwerner@...omium.org>
Cc:	Doug Anderson <dianders@...omium.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	Sonny Rao <sonnyrao@...omium.org>,
	Chris Zhong <zyw@...k-chips.com>,
	Heiko Stuebner <heiko@...ech.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	rtc-linux@...glegroups.com
Subject: Re: [PATCH v2] RTC: RK808: Work around hardware bug on November 31st

Hi Julius, Doug,

On 09/12/2015 at 13:32:52 -0800, Julius Werner wrote :
> > Thinking about all this: these's actually a totally different
> > alternative approach we could take if you wanted.  It would fix S5 and
> > avoid all the anchor stuff, unless I'm crazy.
> >
> > Basically totally give up on the RTC time reflecting reality.  Add a
> > "real time to rk808" and "rk808 time to real time" function.  Always
> > use it when reading from rk808 and always use it when writing to
> > rk808.  Choose 2015 as the "truth" year if you want (or pick another
> > year).  In early 2016 the rk808 always contains 1 day back.  In 2017
> > the rk808 always contains 2 days back.  Etc, etc, etc.
> >
> > The firmware would get confused, but ...
> 
> Well... other than that it's crazy and that I'd have to rewrite the
> whole patch again, I can't come up with a good argument against this.
> In Chromebook firmware the time is only needed for a debug log, so
> we'd probably just be willing to accept it being wrong. If U-Boot ever
> gets RK808 support, they'll probably just copy the Linux driver
> wholesale anyway so they'll conform to the same system.
> 
> So if nobody else raises fundamental objections to this approach, I
> guess I'll get started on another patch version. (Further replies
> below for reference, but most of that stuff would then become moot.)
> 

I'll try to review and evaluate both solution by the end of the week (no
guarantee though).

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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