From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Holler Subject: Re: rtc-twl: catch22 in 2.6.37 and 2.6.38 when clock was never set Date: Tue, 05 Apr 2011 12:14:14 +0200 Message-ID: <4D9AEB76.2060509@ahsoftware.de> References: <4D99D5B0.6010503@ahsoftware.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4D99D5B0.6010503@ahsoftware.de> Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org Cc: linux-omap@vger.kernel.org List-Id: linux-omap@vger.kernel.org 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