Re: [RFC 08/15] rtc: at91sam9: Add missing MFD_SYSCON dependency on HAS_IOMEM

[Arnd Bergmann <arnd@xxxxxxxx>]

On Thursday 03 March 2016 13:27:59 Geert Uytterhoeven wrote:
> On Thu, Mar 3, 2016 at 11:55 AM, Arnd Bergmann <arnd@xxxxxxxx> wrote:
> > On Thursday 03 March 2016 17:03:34 Krzysztof Kozlowski wrote:
> >> index 0da40e2e4280..5c530b6b125d 100644
> >> --- a/drivers/rtc/Kconfig
> >> +++ b/drivers/rtc/Kconfig
> >> @@ -1302,6 +1302,7 @@ config RTC_DRV_AT91RM9200
> >>  config RTC_DRV_AT91SAM9
> >>         tristate "AT91SAM9 RTT as RTC"
> >>         depends on ARCH_AT91 || COMPILE_TEST
> >> +       depends on HAS_IOMEM    # For MFD_SYSCON
> >>         select MFD_SYSCON
> >>         help
> >>           Some AT91SAM9 SoCs provide an RTT (Real Time Timer) block which
> >>
> >
> > This is technically correct, but the entire RTC menu is hidden
> > inside of 'depends on !UML && !S390', so we won't ever get there
> > on any configuration that does not use HAS_IOMEM.
> >
> > If we did, all other RTC drivers would also fail.
> 
> So UML has no RTC. Should/can it use RTC_DRV_GENERIC?

I think nothing should use that, even if it could ;-)

Funny enough, RTC_DRV_GENERIC would probably actually work if you
run UML as root and set iopl() to allow port access, but we don't
really want it to mess with the host RTC.

I don't know where UML gets it real time, but it doesn't actually
need much other than calling clock_gettime(CLOCK_REALTIME, ...)
to get the host time. Presumably it uses some variation of that.

	Arnd
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