[U-Boot] [PATCH 0/4] Add LS1021A-QDS/TWR Non-secure and HYP support.

Li.Xiubo at freescale.com
2014-07-07T03:46:17Z

> >>> [U-Boot,v4,03/10] ARM: non-sec: reset CNTVOFF to zero
> >>>
> >>> Before switching to non-secure, make sure that CNTVOFF is set
> >>> to zero on all CPUs. Otherwise, kernel running in non-secure
> >>> without HYP enabled (hence using virtual timers) may observe
> >> But we have HYP enabled. In this case why are the series dependent on
> >> this patch?
> >>
> > Well, if the HYP is enabled, the host OS will use the Physical timer,
> > and these CNTVOFFs could be cleared in kernel too.
> >
> > When and where to clear them is better ? In uboot or in kernel when needed?
>
> If HYP mode is available CNTVOFF is cleared in Linux. What I am trying
> to say is that it will work also without the patch you mentioned.
>
> Diana

Yes, it will work, but the time won't be correct sometimes till the CNTVOFFs
are cleared in Linux, which we can see from the Linux boot logs with the
following is enabled:

CONFIG_PRINTK_TIME=y

This is because, if the HYP mode is available for Host OS, the Physical timers
Will be used, but the ARCH ARM Timer will still use the Virtual timer's counter
To count the xtime.

Thanks,

BRs
Xiubo