[LinuxBIOS] RTC on geode gx1

ramesh bios ramesh_bios at yahoo.com
Thu Mar 31 04:25:54 CEST 2005

I noticed that, unlike, some of the other
northbridge/southbridge code, the cs5530 code doesn't
do an rtc_init(0). I added that and that now allows me
to set the date. But... I still have weirdness going

RTC Init
RTC: Checksum invalid zeroing cmos
Invalid CMOS LB checksum

So now I'm in the process of reading the rtc_init
code, looking at the board (I know now that my
w83977AF is connected to a 32.768kHz oscillator) and
then figuring out what all the settings mean. That is,
stuff like below. I'm not sure whether the defaults
are good for any board or if they need to be
customized. I guess I'll be finding this out

/* control registers - Moto names
#define RTC_REG_A               10
#define RTC_REG_B               11
#define RTC_REG_C               12
#define RTC_REG_D               13


--- Peter Stuge <stuge-linuxbios at cdy.org> wrote:
> On Tue, Mar 29, 2005 at 07:28:00PM -0800, ramesh
> bios wrote:
> > I'm using the freebios v1 tree on a geode
> > gx1/cs5530a/w83977 with 2.6.11. I noticed that
> there
> > appears to be problem with writing to the RTC
> using
> > hwclock. I seem to be able to use hwclock to set
> the
> > time but not the date. That is:
> There are a few bits in the 5530 at page 107 in the
> data sheet
> regarding the RTC, but I doubt the RTC would be
> reachable at all if
> they weren't ok.
> I just went over the RTC part of the W83977F data
> sheet too and it
> seems to have a couple of control bits that may have
> to be tweaked
> to get proper operation. I don't remember if anyone
> else has had
> similar problems with that superio.
> Besides timing, the only other explanation I can
> think of is that
> since time is stored in RTC registers 00h, 02h and
> 04h, date of month
> in 07h and month/year in 08h-09h, if address bit 3
> wasn't connected
> properly then the date registers would be
> unreachable, but then you
> should see some connection between time and date, so
> lack of proper
> initialization or possibly a timing issue is my
> guess..
> //Peter
> _______________________________________________
> LinuxBIOS mailing list
> LinuxBIOS at openbios.org
> http://www.openbios.org/mailman/listinfo/linuxbios

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