On Fri, 12 Jan 2007, sh_hallmark wrote:
> Where can I find the TS RTC driver mentioned below?
errr..... in the TSA kernel source tree !!!
drivers/char/rtc.c
It's actually only a small conditiional change to the default rtc driver.
happy hacking
Jim
>
>
> --- In Jim Jackson <> wrote:
> >
> >
> >
> >
> > On Tue, 9 Jan 2007, gcworrell wrote:
> >
> > > Hello.
> > >
> > > On our TS-7300's we have found the hw clock drift to be too large
> to
> > > support our objectives. To correct this we have replaced the on-
> board
> > > hw clocks with another. After replacement, on boot, an error
> message
> > > is displayed indicating the hw clock cannot be accessed using any
> known
> > > methods. If you manually run the "hwclock" utility with the debug
> > > option, it says that /dev/rtc cannot be opened because it doesn't
> > > exist. Upon examination, /dev/rtc does not exist.
> >
> > Have you written a driver for it? AFAIK the Linux Kernel hasn't yet
> > been embued with clairvoyance :-)
> >
> > > What is the mechanism whereby the hw clock is discovered and when
> > > is /dev/rtc created? Is there something we need to do to get the
> OS to
> > > recognize the new clock?
> >
> > You write a driver for it in the kernel. Check out the TS RTC one
> as a
> > prototype.
> >
> > But I have to ask - do you mean the HW clock drift? I may be
> teaching my
> > grandmother to suck eggs, but when the kernel is running, the HW
> clock
> > plays no role in timekeeping. The timekeeping is done entirely by
> the
> > kernel, by setting appropriate timer interrupts etc and corrections.
> >
> > On shutdown the system time is written to the HW clock, and on boot
> the
> > kenrel reads to current time from the HW clock - the HW clock drift
> would
> > affect timing accuracy while the board is powered down.
> >
> > I know that when the Technologics first ARM board the TS7200 first
> came
> > out, the kernel timer interrupt config was very poor, and time
> keeping was
> > very poor while running - being many minutes out per day. I fine
> tuned the
> > kernel timer interrupt setting and used the adjtimex to fine adjust
> the
> > kernel timing to better than 1 sec in 5 days (in my pretty constant
> temp.
> > environment).
> >
> > cheers
> > Jim
> >
>
>
>
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