Messages in this thread | | | Date | Tue, 05 Apr 2011 12:14:14 +0200 | From | Alexander Holler <> | Subject | Re: rtc-twl: catch22 in 2.6.37 and 2.6.38 when clock was never set |
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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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