Hello Harald,
On Fri, Nov 27, 2015 at 11:02:54AM +0100, Uwe Kleine-König wrote:
> On Thu, Nov 26, 2015 at 02:39:45PM +0100, Harald Geyer wrote:
> > Uwe Kleine-König writes:
> > > On Wed, Oct 07, 2015 at 12:19:12PM +0000, Harald Geyer wrote:
> > > > This device doesn't provide any information about boot status.
> > > > As workaround we use a persitent bit to track watchdog activity.
> > >
> > > Hmm, so you set a bit in a persistent register iff the watchdog is
> > > running. And if that bit is set during probe you assume the watchdog
> > > reset the machine. But this also happens, when the user presses the
> > > reset button which makes the detection unreliable.
> >
> > Yes, kind of. I'm using this driver on an imx233-olinuxino, where the
> > reset button causes the device to power cycle and thus clears the
> > persitent bit. So I can't test your case, but surely there are some paths
> > into reset, that don't clear the bit and cause false positives.
>
> OK, I found a i.MX28 machine in our repository:
>
> barebox# mw 0x80056080 0xbabecafe
> barebox# boot
> ...
> linux# reboot
> barebox# md 0x80056080+4
> 80056080: babecafe
>
> After a power cycle the value disappears (I didn't check the details, if
> there is a battery it might be empty).
>
> > I have considered gathering some additional information from the
> > power subsystem to refine the result, but decided that it's not
> > worth the complexity. Since the power system is a different silicon
> > block, we can't rely on it being available and would need to provide
> > a fall back implementation anyway.
>
> It would be really nice to get some details about boot rom usage of the
> persistent flags in use. I'd expect that these allow to determine the
> boot source.
A colleague just hinted me to
http://git.pengutronix.de/?p=barebox.git;a=blob;f=drivers/watchdog/im28wd.c;h=3510776a3afc8aaf113eee995900b099c12c2be9;hb=HEAD
which contains a few bit definitions for the i.MX28. Maybe they can help
you to understand your machine better?! At a quick glance there is
nothing that helps you to determine the boot reason, but still it might
contain a few interesting things.
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |
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