[PATCH 1/3] ARM: OMAP2+: 32k-counter: Use hwmod lookup to check presence of 32k timer

[Shilimkar, Santosh]

On Wed, Apr 11, 2012 at 6:30 AM, Ming Lei <tom.leiming at gmail.com> wrote:
> On Tue, Apr 10, 2012 at 5:51 PM, Shilimkar, Santosh
> <santosh.shilimkar at ti.com> wrote:
>> On Tue, Apr 10, 2012 at 2:59 PM, Russell King - ARM Linux
>> <linux at arm.linux.org.uk> wrote:
>>> On Tue, Apr 10, 2012 at 02:27:36PM +0530, Santosh Shilimkar wrote:
>>>> On Tuesday 10 April 2012 02:14 PM, Russell King - ARM Linux wrote:
>>>> > On Mon, Apr 09, 2012 at 03:18:22PM -0500, Jon Hunter wrote:
>>>> >> True, but we would always want to use the 32k timer if CONFIG_PM is
>>>> >> specified. So what I am saying is that if a device has a 32ksync timer
>>>> >> and CONFIG_PM is defined, we always want to use the 32ksync timer and a
>>>> >> gptimer should never be used.
>>>> >
>>>> > Why?  What if you want to have PM enabled, and you also want to use the
>>>> > kernels high resolution timers, or you want more accurate timing than
>>>> > the 30.5us tick interval of the 32k timer?
>>>>
>>>> You might have missed the earlier comments on the thread. High
>>>> resolution GP timer(sysclk) will stop in deeper power states and
>>>> hence it can't be used with PM enabled usecases.
>>>
>>> Which means folk should be given the choice at boot time between running
>>> with the deeper power states and having a higher resolution timing source,
>>> rather than denying them the higher resolution timing source when PM is
>>> enabled.
>>
>> Good point. My point is such facilities is already part of the kernel and
>> there is no need to add a new one. The last proposal was allowing user to
>> choose gptimer as a clocksource and then you already have facility to
>> disable C-state now so, all should work in general
>
> 'nohlt' in boot cmd should work to prevent CPU from entering deep C-state,
> which looks enough to make gptimer working well if system suspend isn't
> considered.
>
That's another good option

Looks like we get all the needed flexibility with the reworked patch
from Vaibhav
to choose the command like option for high res. timer source.

Regards
Santosh