Re: [PATCH v20 08/17] clocksource/drivers/arm_arch_timer: Rework counter frequency detection.

Mark Rutland
2017-01-31T11:42:33Z

On Mon, Jan 30, 2017 at 05:49:59PM +0000, Mark Rutland wrote:
> On Thu, Jan 26, 2017 at 01:49:03PM +0800, Fu Wei wrote:

> > And because Linux kernel is running on Non-secure EL1, so should we
> > skip "SECURE" timer in Linux?
>
> I guess you mean by checking the GTx Common flags, to see if the timer
> is secure? Yes, we must skip those.
>
> Looking further at this, the ACPI spec is sorely lacking any statement
> as to the configuration of CNTCTLBase.{CNTSAR,CNTTIDR,CNTACR}, so it's
> not clear if we can access anything in a frame, even if it is listed as
> being a non-secure timer.

Given CNTNSAR.NS<n> enables non-secure access to CNTACR<n>, I guess the
obvious interpretation is that for frames listed as non-secure, this has
been configured to permit non-secure access to the frame and associated
CNTACR<n>.

I will work to that assumption while reviewing, though I still believe
this needs to be clarified in the spec.

Thanks,
Mark.