[U-Boot] am33xx board with no external RTC crystal issue

[Belisko Marek]

Hi Alex,

On Tue, Oct 30, 2018 at 7:12 AM Alex Kiernan <alex.kiernan at gmail.com> wrote:
>
> On Mon, Oct 29, 2018 at 11:36 PM Belisko Marek <marek.belisko at gmail.com> wrote:
> >
> > Hi,
> >
> > I'm working on custome am33xx based HW which have no external 32KHz
> > crystal. Anyway I want to use bootcount feature. I was trying to use
> > internal PRCM CLK_32KHZ clock as source for RTCSS but still when want
> > to read RTC registers I get data abort.
> >
> > I adapted this method :
> >
> > static void rtc32k_enable(void)
> >  {
> >         struct davinci_rtc *rtc = (struct davinci_rtc *)RTC_BASE;
> >
> >         /*
> >          * Unlock the RTC's registers.  For more details please see the
> >          * RTC_SS section of the TRM.  In order to unlock we need to
> > @@ -287,9 +288,8 @@ static void rtc32k_enable(void)
> >         writel(RTC_KICK1R_WE, &rtc->kick1r);
> >
> >         /* Enable the RTC 32K OSC by setting bits 3 and 6. */
> > -       writel((1 << 3) | (1 << 6), &rtc->osc);
> > +       writel((1 << 6), &rtc->osc);
> >  }
> >
> > to not use external crystal 32KHz clock but internal. Anyway when
> > doing that board just hangs and thats it. Any ideas or suggestions?
>
> I've a board exactly like that... check you're driving RTC_PORz
> correctly, if you hold it in reset, that's the behaviour I see.
OK thanks for info. I think it's hold in reset.
>
> > It
> > is even possible to have something like that? I just seen that
> > include/configs/siemens-am33x-common.h (using also am335x cpu without
> > external 32KHz crystal) storing bootcount to env. Thanks a lot for any
> > pointers.
> >
>
> FWIW I gave up trying to use the internal clock as I couldn't get it
> to tick reliably (my suspicion was my hand modified board wasn't
> actually driving the reset correctly) and instead switched to keeping
> the bootcounter in SRAM.
I'm using bootcount stored in env. I'm using 2017.09 and didn't see
option to store bootcount in RAM (maybe overlooked something).
So you mean bootcount is stored in internal cpu SRAM? Thanks.
>
> --
> Alex Kiernan

BR,

marek



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