[PATCH] clocksource: arm_global_timer: Allow DT to specify already reset timer counter

[Jassi Brar]

On Tue, Dec 15, 2015 at 11:44 PM, Mark Rutland <mark.rutland at arm.com> wrote:
> On Wed, Nov 25, 2015 at 10:54:04AM +0530, Jassi Brar wrote:
>> The GT counter is common to every core in a cluster. There is a usecase
>> when Linux is spawned by a 'master' firmware/OS running on some core of
>> the same cluster and the GT is used by the both.
>>  Linux, upon boot, resetting the GT counter is obviously fatal to the
>> other OS. So provide a way for DT to tell Linux if it's running in that
>> 'slave' mode and must not reset the counter.
>
> Is the other OS only using the counter?
>
I understand only the Global Counter and the (unused) PreScalar are
common to cores in a cluster.

> Or are there other porions of the global timer that it assumes its in
> sole control of?
>
More important than 'control' is the fact that the other OS boots
first. So it can not survive a reset to the global counter.

>> +
>> +** Optional properties:
>> +
>> +- arm,gt_no_reset : Firmware/bootloader already initialized the
>> +     global timer-counter and expects it to be not reset again.
>
> s/_/-/ in property names.
>
> No need for the "gt" prefix, this is on tthe glboal timer node.
>
OK

> It "no-counter-reset" seems like a better description, though that
> really depends on how the other OS is using this.
>
OK will change it to "no-counter-reset".

Thanks.