On Fri, Aug 08, 2014 at 10:20:40AM +0100, Chris Wilson wrote:
> On Tue, Jul 29, 2014 at 12:26:36PM +0200, Daniel Vetter wrote:
> > On Tue, Jul 29, 2014 at 08:37:48AM +0100, Chris Wilson wrote:
> > > On Mon, Jul 28, 2014 at 10:54:06AM +0200, Daniel Vetter wrote:
> > > > On Sat, Jul 26, 2014 at 11:27:38AM +0100, Chris Wilson wrote:
> > > > > On Wed, Jun 18, 2014 at 10:54:13PM +0200, Daniel Vetter wrote:
> > > > > > On Fri, Jun 13, 2014 at 04:38:03PM +0100, oscar.ma...@intel.com
> > > > > > wrote:
> > > > > > > From: Oscar Mateo <oscar.ma...@intel.com>
> > > > > > >
> > > > > > > Or with a spinlock grabbed, because it might sleep, which is not
> > > > > > > a nice thing to do. Instead, do the runtime_pm get/put together
> > > > > > > with the create/destroy request, and handle the forcewake get/put
> > > > > > > directly.
> > > > > > >
> > > > > > > Signed-off-by: Oscar Mateo <oscar.ma...@intel.com>
> > > > > >
> > > > > > Looks like a fixup that should be squashed into relevant earlier
> > > > > > patches.
> > > > >
> > > > > The whole gen6_gt_force_wake_get() calling intel_runtime_pm_get() is
> > > > > broken due to this - we must be able to read registers in atomic
> > > > > context!
> > > > >
> > > > > Please revert c8c8fb33b37766acf6474784b0d5245dab9a1690
> > > >
> > > > force_wake_get can't call runtime_pm_get becuase pm_get can sleep. So if
> > > > you want to read registers from atomic context you have to have a
> > > > runtime
> > > > pm reference from someone else.
> > >
> > > Nope. That cannot work.
> >
> > Well it works currently. So where do you see the problem?
>
> Sampling registers from an timer - in particular, we really do not want
> to disable runtime pm whilst trying to monitor the impact of runtime pm.
In that case you can grab a runtime pm reference iff the device is powered
on already. Which won't call anything scary, just amounts to an
atomic_add_unless or so, and then drop it again.
Unfortunately there doesn't seem to be such a thing around already, so
need to add it first. Greg, how much would you freak out if we add
something like
/**
* pm_runtime_get_unless_suspended - grab a rpm ref if the device is on
*
* Returns true if an rpm ref has been acquire, false otherwise. Can be
* called from atomic context to e.g. sample perfomance counters (where we
* obviously don't want to disturb system state if everything is off atm).
*/
static inline bool pm_runtime_get_unless_suspended(struct device *dev)
{
return atomic_add_unless(&dev->power.usage_count, 1, 0);
}
Cheers, Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
