[PATCH v3] clocksource: arch_timer: Allow the device tree to specify the physical timer

[Doug Anderson]

Hi,

On Mon, Sep 29, 2014 at 10:30 AM, Sonny Rao <sonnyrao at chromium.org> wrote:
> On Fri, Sep 26, 2014 at 3:00 AM, Mark Rutland <mark.rutland at arm.com> wrote:
>> On Thu, Sep 11, 2014 at 06:00:01PM +0100, Doug Anderson wrote:
>>> +** Optional properties:
>>> +
>>> +- arm,use-physical-timer : Don't ever use the virtual timer, just use the
>>> +  physical one.  Only supported for ARM (not ARM64).
>>
>> I'm still not keen on telling the kernel what to do rather than
>> describing the actual state of affairs and having the kernel decide what
>> to do. Perhaps what we actually need is:
>>
>> - cntvoff-not-fw-configured: Firmware does not configure CNTVOFF, which
>>   may reset to (different) arbitrary values on each CPU.
>>
>> This also doesn't describe that CNTHCTL.PL1PC(T)EN must both be 1. While
>> that is the reset state, it still feels dodbgy to me to rely on that.
>>
>> Mark.
>
> Mark, I'm happy to repost it with that name for Doug.
>
> I think it's fair to describe this state in the binding, and if a
> firmware were to put this property into the device-tree for and
> CNTHCTL.PL1P(T)CEN also have configured to 0, then the kernel can
> merely consider that to be a broken usage of this property.   We
> certainly can't protect against all of the possible invalid states
> caused and probably shouldn't try.  If we implement something like
> Christopher's suggestion for transitioning from secure svc to NS hyp
> mode then the kernel can simply ignore this property at that point.

I've already talked in person to Sonny about this, but just to post on
the list too...  I think Mark Rutland's suggestion is a good one and
I'm more than happy for Sonny to repost that way for me.  Thanks!  :)

-Doug