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* rtc-twl: catch22 in 2.6.37 and 2.6.38 when clock was never set
@ 2011-04-04 14:29 Alexander Holler
  2011-04-05 10:14 ` Alexander Holler
  0 siblings, 1 reply; 12+ messages in thread
From: Alexander Holler @ 2011-04-04 14:29 UTC (permalink / raw)
  To: linux-kernel; +Cc: linux-omap

Hello,

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.

Regards,

Alexander Holler

^ permalink raw reply	[flat|nested] 12+ messages in thread

end of thread, other threads:[~2011-06-09  9:23 UTC | newest]

Thread overview: 12+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2011-04-04 14:29 rtc-twl: catch22 in 2.6.37 and 2.6.38 when clock was never set Alexander Holler
2011-04-05 10:14 ` Alexander Holler
2011-04-05 13:40   ` [PATCH] arm: omap3: beagle: Ensure msecure is mux'd to be able to set the RTC Alexander Holler
2011-05-31 10:29     ` Tony Lindgren
2011-06-07  8:01       ` Alexander Holler
2011-06-07  9:50         ` Igor Grinberg
2011-06-07 11:15           ` Alexander Holler
2011-06-08 21:57             ` Igor Grinberg
2011-06-09  0:21               ` Alexander Holler
2011-06-09  7:40                 ` Igor Grinberg
2011-06-09  9:23                   ` Alexander Holler
2011-05-31 10:28   ` rtc-twl: catch22 in 2.6.37 and 2.6.38 when clock was never set Tony Lindgren

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