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

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Date:	Fri, 8 Jan 2016 10:15:51 -0800
From:	Tony Lindgren <tony@...mide.com>
To:	"H. Nikolaus Schaller" <hns@...delico.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

* 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?

Regards,

Tony