linux-kernel - Re: rtc-twl: catch22 in 2.6.37 and 2.6.38 when clock was never set

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Date:	Tue, 05 Apr 2011 12:14:14 +0200
From:	Alexander Holler <holler@...oftware.de>
To:	linux-kernel@...r.kernel.org
CC:	linux-omap@...r.kernel.org
Subject: Re: rtc-twl: catch22 in 2.6.37 and 2.6.38 when clock was never set

Hello,

Am 04.04.2011 16:29, schrieb Alexander Holler:

> it just happened here that the rechargeable backup battery for the RTC
> on a TPS65950 run out off power, because of some days while the device
> wasn't powered.
>
> Afterwards I couldn't read or set the clock with hwclock using a kernel
> 2.6.37.n or 2.6.38.n.
>
> I don't have a fix, but I think I've analyzed the problem and can offer
> a (bad) workaround.
>
> What happens is the following:
>
> When trying to read or set the clock with hwclock, the driver (rtc-twl)
> starts an alarm, but the irq for the alarm will never get called. The
> result is that a select in hwclock times out (for both operations, read
> or set).
>
> Because I had this clock running before, I've got the idea to try one of
> those old OMAP-kernels (2.6.32-angstrom) using the same userland.
> And with that kernel I could set the clock.
> Using 2.6.37 or 2.6.38 afterwards, hwclock did function again, both read
> an set are working.
>
> So it looks like there is a catch22 in kernels >=2.6.37 (I haven't
> tested .33-.36):
>
> When the clock was never set, the alarm(-irq) doesn't work, so hwclock
> doesn't work, so one can't set the clock.

It turns out that the missing/wrong initialization of the msecure line 
is the problem which disabled setting the clock. After doing that 
through a quick hack, I could set the clock.

I'm using a BeagleBoard C4, but I can't find any msecure initialization 
for other boards too.

What happened with those patches? E.g. those:

http://www.mail-archive.com/linux-omap@vger.kernel.org/msg16125.html

Regards,

Alexander
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