On Thursday 03 March 2016 13:27:59 Geert Uytterhoeven wrote:

On Thu, Mar 3, 2016 at 11:55 AM, Arnd Bergmann [off-list ref] wrote:

quoted

On Thursday 03 March 2016 17:03:34 Krzysztof Kozlowski wrote:

quoted

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