On 6/12/14, 8:01 PM, "Robert Nelson" <robertcnel...@gmail.com> wrote:
>On Thu, Jun 12, 2014 at 9:56 PM, Justin Morgan <jdm...@gmail.com> wrote: >> I've noticed a difference in behavior between the latest Angstrom Linux >> image and the latest Debian image available for the BeagleBone Black >>when it >> comes to enumerating the real-time clocks present when a RTC "Cape" is >> "present". [I have the actual clock present by use of a generic breakout >> board, but not the actual cape.] >> >> I am trying to determine if Angstrom Linux has a patch that is not >>present >> in Debian, as I prefer the RTC behavior I am seeing in Angstrom. (I'd >>think >> Debian would want the Angstrom behavior, because if the user has >>attached an >> RTC, then there is most likely a battery backing it; the BBB currently >>does >> not support shutdown to the RTC rail only, so the on-board RTC is going >>to >> be wrong on a cold boot.) >> >> When I tell Angstrom that I have a "BB-BONE-RTC" cape attached, my RTC >>(the >> DS1307) is enumerated as /dev/rtc0. As such, my clock becomes the clock >>that >> is used to set the system clock, and is otherwise going to get all of >>the >> privileges of being the first RTC. >> >> When I tell Debian that I have a "BBB-RTC-01" cape attached, the >>on-board >> RTC is still enumerated as /dev/rtc0. My RTC is enumerated as >>/dev/rtc1. As >> such, the clock is wrong on boot. >> >> I used different capes because I was going for firmware already on the >>BBB. >> I don't see anything about either DTO that explains the difference in >> behavior. > >Well, i just compared Angstrom's config with the one i've been pushing >out for our 3.8 branch.. No difference an any "RTC" config's.. > >Probally comes down to Angstrom's much newer version of systemd, or >something custom. Is systemd really creating /dev/rtc0? Isn't initcall starting the driver and posting an event to udev which then creates /dev/rtc0. I think this is simply a race condition on which driver gets started first. Here is a test that Justin can do to resolve this. Add ³initial_debug² to his kernel command line (on both Debian and Angstrom) and after he has booted each BBB OS, see which driver gets started first by running the ³dmesg" command. Regards, John > >Regards, > >-- >Robert Nelson >http://www.rcn-ee.com/ > >-- >For more options, visit http://beagleboard.org/discuss >--- >You received this message because you are subscribed to the Google Groups >"BeagleBoard" group. >To unsubscribe from this group and stop receiving emails from it, send an >email to beagleboard+unsubscr...@googlegroups.com. >For more options, visit https://groups.google.com/d/optout. -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
