linux-kernel - Re: [PATCH 1/3] ARM: dts: omap5-board-common: enable rtc and charging of backup battery

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Message-Id: <832803EE-E4CB-46B1-BF39-2DC0BB695A5D@goldelico.com>
Date:	Fri, 8 Jan 2016 19:32:54 +0100
From:	"H. Nikolaus Schaller" <hns@...delico.com>
To:	Tony Lindgren <tony@...mide.com>
Cc:	Laxman Dewangan <ldewangan@...dia.com>, Nishanth Menon <nm@...com>,
	Benoît Cousson <bcousson@...libre.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	linux-omap <linux-omap@...r.kernel.org>,
	devicetree@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	Marek Belisko <marek@...delico.com>
Subject: Re: [PATCH 1/3] ARM: dts: omap5-board-common: enable rtc and charging of backup battery


Am 08.01.2016 um 19:15 schrieb Tony Lindgren <tony@...mide.com>:

> * H. Nikolaus Schaller <hns@...delico.com> [160108 09:50]:
>> Tony,
>> it is strange. It now works under unknown conditions - without any obvoius change.
>> 
>> Am 06.01.2016 um 18:09 schrieb Tony Lindgren <tony@...mide.com>:
>>> 
>>> OK. It could be also some .config change with something built-in?
>> 
>> I have compared /proc/config.gz from both systems and /sys/firmware/fdt
>> with no significant and obvious change.
>> 
>> Then I booted the 4.4-rc8 again and this time it worked.
>> 
>> To verify, I have checked out linux-next this morning, cherry-picked this palmas
>> rtc patch, compiled with omap2plus defconfig, and used the omap5-uevm.dtb. And
>> hwclock works after doing a modprobe rtc_palmas.
> 
> Weird. No luck here with current linux next or anything.
> 
>> Then I did the same with official v4.4-rc8 and hwclock hangs. And now our
>> 4.4-rc8 production kernel hangs again as well. Even if I use the
>> DTB from the 4.3 kernel.
> 
> I'm not seeing the RTC second increase in u-boot either, this
> should show it:
> 
> # i2c md 0x48 0x100
> 
> Of course the rtc may not be enabled in u-boot unlike for x15.
> 
>> So I think it is something which is unstable in 4.4-rc8 that is (probably) fixed in
>> linux-next and unrelated to this DT patch.
>> 
>> But I have no hint or idea what it is.
> 
> Or something hangs the RTC? And the back-up battery has to drain to
> reset the RTC somehow?

Indeed it could be something like this. I already suspected that it depends
on boot order of some components.

But you get the /dev/rtc and /sys/class/rtc nodes? This is what this patch
should enable (and not fix potential driver issues).

BR,
Nikolaus