From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: 405LP RTC reset From: Hollis Blanchard To: David Gibson Cc: embedded list , Todd Poynor In-Reply-To: <20021218005542.GC3666@zax.zax> References: <1040150612.10740.111.camel@granite.austin.ibm.com> <20021218005542.GC3666@zax.zax> Date: 18 Dec 2002 09:38:53 -0600 Message-Id: <1040225939.29647.11.camel@granite.austin.ibm.com> Mime-Version: 1.0 Content-Type: text/plain Sender: owner-linuxppc-embedded@lists.linuxppc.org List-Id: On Tue, 2002-12-17 at 18:55, David Gibson wrote: > > On Tue, Dec 17, 2002 at 12:43:32PM -0600, Hollis Blanchard wrote: > > Here's the updated 405LP RTC reset diff (after David's move of the RTC > > functions to ibm405lp.c). This patch > > a) does a full RTC reset as specified in the docs > > b) sets the RTC clock speed in RTC "Register A" DV bits, i.e. it does > > not assume the firmware has done this correctly. > > One query though (I didn't think of this earlier) - is it such a great > idea to go setting the reference clock frequency? Unlike most other > drivers, we can't just take over the RTC and do what we like with it > once the kernel boots, because it has to keep running at the same rate > even when the device is rebooting or (mostly) off. The only issue I can think of here is the firmware setting it incorrectly or not at all. In that case, a few seconds will be expanded or compressed, but that's better than time running too fast or slow forever, right? Of course the rate settings must be battery-backed along with the time, so you only need to set it once per RTC power loss. That includes rebooting time and power off time. -Hollis -- PowerPC Linux IBM Linux Technology Center ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/